Electrical Systems
The general rules regarding Multiple Conductors in One Lug do not apply if
The manufacturer's instructions on the panelboard label state something different.
Enclosures installed outdoors or indoors in a damp location should have at least a
¼ inch air space behind the enclosure to allow drying and to avoid condensation; this feature is usually built into the back of the cabinet by making the attachment openings protrude.
Common sizes for ENT range from
½ to 2 inches diameter.
Common sizes for FMC range from
½ to 4 inches diameter.
Common sizes for PVC range from
½ to 6 inches diameter.
Industry convention places wall receptacles at about
12 inches above the floor and countertop receptacles at about 45 inches above the floor, but these heights are not required.
Surface-mounted incandescent and LED fixtures should not be located within
12 inches from the closet storage areas.
GFCI protected residential branch circuits at 20 amps or less may be buried at least
12 inches regardless of the wiring method.
A dishwasher and food-waste disposer may each need a dedicated
120 volt circuit.
In residential electrical systems, the voltage between the hot (ungrounded) wires and the neutral (grounded) wire is
120 volts.
Most lights in houses operate on
120 volts.
Receptacles on 15 amp general lighting and receptacle branch circuits should be
15 amp rated receptacles.
ENT should be supported every
3 feet and within 3 feet from boxes and terminations.
PVC should be supported every
3 feet for 1 inch and smaller sizes, 5 feet for 1¼ inch and larger sizes, and within 3 feet from boxes and terminations.
These devices measure the current flow between the energized and neutral wires and trip if they detect a difference of about
6 milliamperes or more (a ground fault).
The Edison base fuse is an older fuse that screws into
A round fuse holder.
If electricity flows where not intended, like between copper and aluminum wires or between aluminum wires and steel terminals intended for copper wires,
Corrosion can occur.
The bend radius of cables such as AC and NM should not be less than
Five times the cable diameter.
NM may not be installed
Outdoors, including inside conduit and tubing that is installed outdoors and conduit and tubing that is buried. These are considered wet locations.
Appliances listed for cord-and-plug connection may use the plug as the disconnecting means.
Examples include food-waste disposers, trash compactors, dishwashers, and microwave ovens.
Liquidtight Flexible Metal Conduit (LFMC) and Liquidtight Flexible Conduit (LFC) are
Flexible tubes designed for routing and protection of conductors and cables, specifically for use where water is an issue.
Interior receptacles may be installed in
Floors (with listed floor boxes), in ceilings, or anywhere in between.
If the service equipment is in a different cabinet from the main panelboard, the conductors between the service equipment and the main panelboard are called
Feeder conductors.
AFCIs protect structures from
Fire
Carbon monoxide alarms have a shorter service life of around
Five to seven years.
The two primary general concerns regarding light fixture installation are
Fixture support and grounding of exposed metal.
ENT should be protected by
Nail guards when run closer than 1¼ inches to the edge of a framing member such as a stud or a joist.
MC should be protected by
Nail guards when run closer than 1¼ inches to the edge of a framing member such as a stud or a joist.
NM should be protected by
Nail guards when run closer than 1¼ inches to the edge of a framing member such as a stud or a joist.
Energized neutral conductors not marked as energized
Neutral conductors may be used as energized conductors, but they must be permanently marked in the enclosure and at all accessible points; this is usually done with electrical tape or a black marker.
Fused neutral
Neutral conductors should not be connected to OPDs because in the unlikely event that the OPD opens the neutral conductor, current flow will stop but the circuit will remain energized; this is usually an issue only for very old electrical systems.
EGCs should not be connected to the neutral terminal bars.
Neutral terminal bars should not be connected to the subpanel enclosure.
AFCIs should be installed on
New branch circuits and when branch circuits are extended or modified.
The second rule, and last, to updating the electrical system is
New work and existing work that is modified or extended should comply with rules in effect when the work is done. This second rule applies regardless of whether a permit was required or issued.
Bonding jumpers must be installed around interruptions such as
Plastic boxes, water meters, and sometimes components such as water softeners and filters.
Screws with points used to secure enclosure covers
Points could penetrate conductor insulation and energize the enclosure.
Industry convention installs receptacles with the grounding slot down, but this is not required.
Some electricians install wall receptacles with the grounding slot up to indicate a switched receptacle.
Fires often start in one of two ways.
Some fires start by producing a lot of flame but little smoke. Some fires start by producing a lot of smoke but little flame. There are two types of smoke alarms.
Intermediate Metal Conduit (IMC) and Rigid Metal Conduit (RMC) are
Round pipes designed for routing and physical protection of conductors and cables.
Some switches have a small LED light in the switch for
Safety and convenience at night.
PVC comes in two wall thicknesses
Schedule 40 and Schedule 80. Schedule 80 should be used when protection against physical damage is necessary.
Load center
See Panel (panelboard, load center).
All neutral conductors (current-carrying) should be connected to
Separate neutral terminal bars or lugs that are isolated from the EGCs and from the enclosure.
Cartridge fuses are sometimes found as
Service equipment in old circuit breaker-equipped panels, in service equipment switches, and in disconnect boxes for HVAC equipment.
Like all devices, circuit breakers have a finite service life.
Service life estimates for circuit breakers range between 30 and 50 years.
Switches also include a wide variety of dimmers that are used to control light output from lamps and to control ceiling fan speed.
Several dimmer types are available including rheostats (old technology), and various types of solid state dimmers. Several dimmer styles are available including rotary, push button, and slide.
A clothes closet is one that contains
Shelves or rods designed for storage of clothing. Pantries and similar storage closets are not included in this section.
Twenty amp rated receptacles may be identified by a
Short notch perpendicular to the neutral slot.
Electricity in almost all residential electrical systems
Single phase 240/120 volts.
Most house panelboards are
Single-bus panelboards.
Disconnecting all electricity to a house should require operating or pulling no more than
Six circuit breakers, fuse blocks, and switches in any combination. The service equipment should be labeled to indicate its function, and it should be listed for use as service equipment.
A photoelectric alarm works by shining a light above a sensor at a 90° angle to the light.
Smoke entering the alarm disrupts the light, reflects some of the light toward the sensor, and triggers the alarm.
An ionization alarm works by using radioactive material to ionize the area between two sensors and allow the flow of electricity between the sensors.
Smoke entering the sensor disrupts the flow of electricity and triggers the alarm.
Ionization alarms are significantly less responsive at detecting
Smoky fires, and, in fact, may not activate until it is too late, if at all. They are significantly less responsive at detecting smoky fires, and, in fact, may not activate until it is too late, if at all.
In modern houses, most switches are either
Snap switches or Rocker switches.
Copper-clad aluminum wire does not share the same problems as
Solid-conductor aluminum wire and has not been a problem. It is also uncommon, which may explain why there have been no reported problems
The majority opinion among experienced home inspectors is split regarding these Bulldog Pushmatic panelboards.
Some believe there is insufficient evidence to warrant reporting the presence of these panelboards. Others believe that reporting the presence of these panelboards from the 1950s and 1960s is warranted if for no other reason than advanced age, and because listed replacement parts may be difficult to find and may be expensive.
The other problem with aluminum expanding more than copper when the wire gets hot was that over multiple expansion and contraction cycles, aluminum wire at the connections would become distorted, smaller, and brittle, permanently.
Some call this problem cold flow while others call it creep.
Home inspectors are not required to test AFCI devices.
Some do so in unoccupied buildings; many do not test devices in occupied buildings citing the risk of inconvenience to occupants and damage to equipment connected to the circuit when electricity is disrupted.
The substantial majority opinion among experienced home inspectors is to report the presence of these Federal Pacific Stab-Lok panelboards, explain the potential risks, and recommend evaluation by a qualified electrician; however
Some electricians are not aware of the alleged problems with these panelboards, so some home inspectors recommend replacing these panelboards.
The majority opinion among experienced home inspectors is to report the presence of the Zinsco/Zinsco-Sylvania panelboards, explain the potential risks, and recommend evaluation by a qualified electrician.
Some electricians are not aware of the alleged problems with these panelboards.
These home inspectors believe it is prudent to report the presence of the Bulldog Pushmatic panelboards, explain the potential risks, and recommend evaluation by a qualified electrician.
Some electricians are not aware of the alleged problems with these panelboards.
There is some disagreement about which test method is best; however, the GFCI receptacle manufacturers recommend using the TEST button.
Using the TEST button is recommended; also using the receptacle tester does no harm.
Three phase 240 volt and three phase 208 volt residential services are
Very uncommon for houses.
Wall space includes any wall more than 2 feet wide, fixed panels of doors, partial height walls, and room dividers such as railings.
Wall space does not include obstructions such as fireplaces and closets.
A fuse contains a strip of metal that is designed to melt when current flow exceeds a set amount for a set time period.
When the metal melts the current flow stops and an electrical fire is prevented.
Examples of situations when a home inspector may elect not to inspect an electrical enclosure interior include
When the panelboard was manufactured by a company that produced problematic panelboards and when access to the enclosure is blocked by owner belongings or is otherwise not safely accessible.
Modern NM jacket is color-coded to identify the wire gauge.
White = #14, Yellow = #12, Orange = #10, Black = #8 and #6.
Wind consistency and speed are the important environmental components in determining whether a wind turbine is practical.
Wind speed is assumed between 24 and 26 miles per hour when rating the electricity output of wind turbine generators. An average wind speed of at least 10 miles per hour is a recommended minimum.
Modern wind turbine electricity generating systems are the direct descendants of
Windmills that have been used for hundreds of years for applications such as pumping water and grinding grain.
Home inspectors should inspect inside disconnecting means enclosures that have fuse blocks and pull tabs.
Wiring defects such as damaged conductors and improper taps to serve other outlets are not common but can occur.
A multiwire branch circuit is a three wire branch circuit
With two hot (ungrounded) wires and one neutral (grounded) wire.
Tin-coated copper wire was most popular in the 1940s and 1950s.
You could find it in older houses too, and in houses built as late as the 1960s.
When a multiwire branch circuit is operating as intended, the voltage on the shared neutral (grounded) wire is
Zero.
Edison fuses are no longer
permitted for new installations.
Receptacles are not required behind sinks and cooking appliances unless
the countertop behind the sink or appliances is deeper than 12 inches.
EMT may serve as the
EGC when appropriate fittings are used.
LFC is made from
PVC
Exterior stairways to a basement should have the light at
The bottom landing.
A load calculation assumes that all electric circuits are not active simultaneously; thus, the calculated load is less than the sum of all circuits in the house, or all circuits served by a subpanel. The calculation is the sum of the following:
(1) The load of light and receptacle circuits (2) The load of kitchen and laundry receptacle circuits (3) The load of electric appliances such as the electric clothes dryer, water heater, and cooking appliances (4) The load of the largest heating or cooling equipment such as all air conditioning or heat pump condensers or electric space heating. The loads for numbers 1, 2, and 3 are reduced by a factor that accounts for circuits not being active simultaneously.
Smoke alarm and carbon monoxide alarm installation requirements include:
(1) connection of all smoke alarms to each other such that if one alarm is activated all alarms sound (interconnection may be hard wired or wireless) (2) primary power provided by the utility power to the building (3) back-up power provided by a battery in case the fire disrupts the utility power to the building. Carbon monoxide alarm interconnection is a new requirement, so most houses will not comply.
The grounding electrode system of a house's electrical system consists of:
(1) grounding electrode(s) and, (2) a grounding electrode conductor (GEC). Common grounding electrodes include: •at least 20 feet of #4 rebar or #4 AWG bare copper wire encased in concrete (a ufer ground), •a galvanized steel pipe or rod, or a copper-coated steel rod driven at least eight feet into the ground, •a metal water service pipe (including metal well casings) in contact with the ground for at least ten feet.
Flexible cords are cables that are usually:
(1) made from stranded conductors, (2) terminate with an attachment plug, (3) intended to connect an appliance to an outlet that is usually a receptacle. Flexible cords include extension cords.
Correctly installed knob and tube wiring should have these characteristics. Knob and tube wiring that does not comply with these is a reportable deficiency.
1. At least 1 inch distance between the wires and objects like walls, floors, and framing. 2. At least 3 inches distance between the wires. 3. Not more than 6 inches between knobs and a wire splice, including splices in boxes. 4. Not more than 4 ½ feet between knobs in wire runs. 5. Wires run on the sides of joists, rafters, and studs, not on top. 6. Tubes installed where the wires penetrate framing. 7. Taps between knob and tube wires and other knob and tube wires may occur outside of covered junction boxes. The taps should be soldered and taped using friction tape. 8. Taps between knob and tube wires and other wiring methods should occur inside a covered junction box or conduit body. 9. Wiring methods should enter boxes with appropriate protection and should be secured near the box as required. Each knob and tube wire should enter the box through a separate opening protected by a bushing. NM cable should enter the box through a clamped opening and should be secured within 12 inches from the box.
Typical defects for grounding and bonding that home inspectors should report include:
1. Damaged, disconnected, loose GEC at grounding electrode connection, 2. GEC too small for service (minimum #8 copper for under 150 amp service and #4 or #6 copper for 150 amp or larger service), 3. Absent, loose grounding or bonding clamp, 4. Grounding or bonding clamp connected to surfaces that are corroded, painted, dirty, or are covered by other high-resistance contaminants, 5. GEC improperly spliced; GEC may be spliced using a listed compression connector or by welding (not soldering), 6. Metallic conduit connected with plastic fittings (electrical connection disrupted), 7. Underground water pipe GEC connection located more than 5 feet from where water pipe enters the house (do not confuse this with the water distribution pipe bonding connection), 8. Absent, loose, broken metal conduit connections (bonding path interrupted by absent or poor physical or electrical connection), 9. Absent, loose, corroded metal water pipe bonding connection, 10. Bonding jumper absent around water meter, water pressure regulator, water softeners and filters, and similar removable non-metallic components in metal water distribution pipes, 11. Improper bonding connection installed for phone, cable, or similar services, 12. CSST gas tubing not bonded at first metal gas pipe or fitting after gas meter.
Typical Defects, Subpanels: Typical defects that home inspectors should report include:
1. EGCs and neutral conductors are connected to the same terminal bar, 2. EGCs or EGC terminal bar is not bonded to enclosure, 3. Refer to Other Typical Defects Inside Enclosures.
Typical Defects, Light Fixture and Ceiling Fans
1. Loose fixture or fan 2. Damaged, scorched, aged, fixture or fan 3. Absent parts 4. Exposed conductors in a fixture or fan box 5. Gap between light fixture and wall or ceiling 6. Damp or wet area fixture not installed where required 7. Interior fixture or fan installed outdoors 8. Inadequately supported fixture or fan 9. Fixture or fan does not function using nearby switches 10. Hanging fixture or ceiling fan too close to tub or shower 11. Fixture too close to clothes closet storage area 12. Exposed incandescent bulb in clothes closet 13. Recessed light operates intermittently 14. Ceiling fan unbalanced, wobbles.
Typical Defects, Receptacles
1. Loose receptacles (e.g., receptacle moves when plug inserted) 2. Damaged, scorched, aged/worn, or painted receptacles (e.g., plug falls out of receptacle) 3. Absent, damaged, or loose cover plates 4. Gap between receptacle and cover plate or between cover plate and wall 5. Damp or wet area cover not installed where required, or cover damaged 6. Receptacle connected to an improper branch circuit, (e.g., receptacle not in a bathroom is on the bathroom branch circuit) 7. Inadequately supported boxes 8. Improperly wired receptacles, (e.g., reverse polarity, not grounded, open neutral) 9. No power at receptacles 10. Receptacle ampacity rating not compatible with branch circuit 11. Receptacle not installed where required, (e.g., kitchen countertop receptacles too far apart) 12. Receptacle installed where not allowed, (e.g., above bathtub 13. Receptacles not AFCI or GFCI protected where required.
Typical Defects, Switches
1. Loose switches (e.g., switch moves when operated) 2. Damaged, scorched, aged/worn, or painted switches (e.g., switch makes noise (arcs) when operated 3. Absent, damaged, or loose cover plate 4. Gap between switch and cover plate or between cover plate and wall 5. Damp or wet area cover not installed where required, or cover is damaged 6. Inadequately supported switch box 7. No power at switch 8. 3-way and 4-way switches do not function properly in all switch positions 9. Dimmer switches do not function properly 10. Switch installed where not allowed (e.g., above bathtub) 11. Switch operates intermittently 12. Switch unusually warm 13. Switch appears to control a load greater than its ampacity rating 14. Switch installed upside down 15. Switch located behind a door or in another inconvenient location.
Bonding occurs when:
1. Metal that could carry electricity (but is not supposed to) 2. Is intentionally connected together to provide a permanent low resistance return path 3. That is capable of conducting all electricity accidentally carried by the metal back to its source.
Typical Defects for PV Systems:
1. PV system disconnected or not functioning (display on inverter usually shows system status) 2. Backfed PV circuit breaker not secured in panelboard 3. Components not labeled 4. Absent disconnect switches 5. Exposed conductors (except where intended) 6. Array tracking module not functioning (difficult to determine during a home inspection) 7. Metal components not bonded, or gaps in component physical or electrical connection 8. Panels cover vents and exhaust terminations (okay if space between panel and vent or termination at least as large as the opening) 9. Damaged panels including scratches on glass 10. Significant shading of arrays (may be accounted for in the system design).
Typical defects for electrical service that home inspectors should report include:
1. Service drop conductors in and around tree limbs, 2. Damaged service drop and service entrance conductor insulation, 3. No insulation at service drop connection to service entrance conductors, 4. Drip loops inadequate to drain water, 5. Loose, bent, or damaged service mast or service head 6. Absent, deteriorated, damaged, improperly installed service mast flashing, 7. Loose or damaged service drop connection at house, 8. Inadequate clearances between service drop and service entrance conductors and roofs, ground, and building openings, 9. Loose, damaged, deteriorated meter bases and electrical enclosures, 10. Meter bases and electrical enclosures not sealed where attached to wall coverings, this is a water infiltration point, 11. Loose or damaged conduit at or around enclosures, 12. Service equipment and panelboard upgraded to larger capacity, but service drop and service entrance conductors not changed.
Typical defects that home inspectors should report include:
1. Splices and taps not contained within an approved and covered box, 2. Box does not have an approved cover, 3. Box knockout does not have an approved cover, 4. Cable enters box without intact sheathing, at least ¼ inch of sheathing should enter the box, 5. Junction box concealed (usually not visible), 6.Wiring method not properly secured near box or enclosure or not secured along run, 7. Wiring method not protected against physical damage, 8. Wiring method installed outside and not approved for outside installation, 9. NM and AC cable installed outside or in buried conduit, 10. Cable or conductors enter metal box without cable clamp or busing, 11. Metal box not grounded (bonded), 12. Wiring method deteriorated or damaged, 13. Cable or conductors repaired with electrical tape or with other unapproved material, 14. Conduit loose at or around enclosures, 15. Extension cord used as permanent wiring, 16. Attachment plug provides electricity to permanent wiring method, 17. Flexible cord passes through or installed in a ceiling, wall, or floor.
Solar water Heating Typical Defects
1. System disconnected or not functioning (improper functioning may be difficult to visually determine), 2. Absent backflow preventer, 3. Absent or improperly installed pressure relief valve, temperature/pressure relief valve, or extension pipe, 4. Absent, improperly installed, or deteriorated pipe insulation, 5. Leaks from or inside collector, and leaks from pipes, 6. Damaged or corroded components, 7. Absent expansion tank where required, 8. Shading of collector, 9. Dirt on collector, 10. Leaks at roof mounts (for roof-mounted collectors), 11. Deformed roof framing (roof-mounted collectors filled with water are heavy), 12. Absent labels where required, such as at on collectors, on storage tanks, and at drain and fill valves.
There is much more to grounding and bonding. For home inspectors, this is the easiest way to think about them.
1. The grounding system of the house acts like a voltage surge suppressor that helps safely shunt voltage surges to ground. 2. Bonding is a safety system that helps clear ground faults in normally non-current carrying materials.
Typical Defects Wind Turbines
1. Wind system disconnected or not functioning (display on inverter usually shows system status), 2. Backfed wind circuit breaker not secured in panelboard, 3. Components not labeled, 4. Absent disconnect switches, 5. Exposed conductors (except where intended), 6. Metal components not bonded, or gaps in component physical or electrical connection, 7. Tower not grounded, 8. Damaged or deteriorated components, 9. Surge protector not installed.
EMT should be supported every
10 feet and within 3 feet from boxes and terminations.
IMC and RMC should be supported every
10 feet and within 3 feet from boxes and terminations.
The minimum distance between the lowest individual service drop or service entrance conductor and the ground or a pedestrian walkway is
10 feet.
The minimum electrical service current for a modern single-family house is
100 amps. Anything smaller is considered a reportable deficiency, even if the service is original.
For example, a fixed in place appliance should not be rated at more than 7.5 amps and a plug and cord connected appliance should not be rated at more than
12 amps on a 15 amp, 120 volt general lighting branch circuit.
The minimum distance above a residential driveway is
12 feet.
AFCI protection is now required for most
15 and 20 amp, 120 volt branch circuits in houses. The primary exceptions include circuits serving bathrooms, laundry rooms, basements, crawl spaces, garages, and the outdoors.
Switches for use by people with disabilities are usually located between
15 and 48 inches above the floor, depending on whether an obstruction is in front of the switch.
Many detached buildings are served by a single
15 or 20 amp branch circuit.
Receptacles on 20 amp general lighting and receptacle branch circuits should be
15 or 20 amp rated receptacles.
Lighting branch circuits in houses are restricted to
15 or 20 amps, 120 volts.
Receptacles serving general lighting and receptacle branch circuits are limited to those rated at
15 or 20 amps.
The minimum distance above a public street and above areas subject to truck traffic is
18 feet.
Floor receptacles may be used to comply if the receptacle is within
18 inches from the wall.
An exception reduces the minimum distance between the service drop and the roof to
18 inches if less than 6 feet of the service drop conductors extend above the roof (measured along the conductors), and if the service drop conductors extend above no more than 4 feet of the roof (measured along the roof). The 18 inch clearance is the most common distance seen in the field. Service drop clearances may be changed by additions to the house such as new rooms and porch roofs.
AC may be found in houses from the early
1900s to new construction.
Metal-clad Cable (MC) may be found in houses from the early
1900s to new construction.
Receptacle types began to be standardized in the
1930s through the efforts of the National Electrical Manufacturers Association (NEMA).
These Bulldog Pushmatic panelboards are most common in houses built in the
1950s and 1960s, but they may be found in homes built up to the 1990s.
FMC should be protected by nail guards when run closer than
1¼ inches to the edge of a framing member such as a stud or a joist.
LFMC and LFC should be protected by nail guards when run closer than
1¼ inches to the edge of a framing member such as a stud or a joist.
GFCI protected receptacles serving walls above kitchen countertops should be spaced so that no point along the wall above the countertop is more than
2 feet from a receptacle. This means receptacles are often spaced about every 4 feet.
At least one GFCI protected receptacle should be located at a peninsula if it measures more than
2 feet long (measured from the perpendicular wall closest to the peninsula) and 1 foot wide.
The required countertop receptacles should not be located more than
20 inches above the countertop or in an enclosed space such as an appliance garage. Receptacles may be located in these areas, but they do not count as one of the required receptacles
The minimum distance above a swimming pool is
22½ feet above the water and extending 10 feet in all directions from the pool edge.
Almost all utility-supplied residential electrical service is
240 volt single phase.
In residential electrical systems, the voltage between the two hot (ungrounded) wires is
240 volts
Hanging light fixtures, track lights, and ceiling fans should have no parts located within a zone from
3 feet horizontally and 8 feet vertically from the tub rim or shower threshold. No parts includes nonconductive parts such as glass and fan blades.
The minimum distance for a roof with a slope 4/12 or greater is
3 feet.
The minimum distance between the lowest individual service drop or service entrance conductor and the side or sill of an operable window, door, deck, balcony, or similar point is
3 feet. The lowest point is usually the drip loops
Recessed lights that are not IC rated should have at least
3 inches of space between the light and insulation.
In modern houses, the 120 volt receptacles will be the
3-slot grounded polarized receptacle.
Modern receptacles should be
3-slot grounded receptacles, and should be tamper-resistant receptacles. Existing receptacles may remain, but if replaced, the new receptacles should comply with modern standards.
The current rating of a fuse is color coded:
30 amp = green, 25 amp = green or yellow, 20 amp = orange or red, 15 amp = blue or purple, 10 amp = yellow or slate (can appear gray).
SE should be supported every
30 inches and within 12 inches from boxes and terminations.
The service equipment, panelboards, and equipment disconnect devices should have clear working space in front that is at least
36 inches deep, 30 inches wide, and 78 inches tall, measured from the floor.
The maximum flexible cord length is:
36 inches for a food-waste disposer. 48 inches for a range hood and a trash compactor. 78 inches for a built-in dishwashing machine.
Light fixtures controlled from three or more locations require a 3-way switch at each end of the circuit and
4-way switches in the middle.
Industry convention locates wall switches at about
48 inches above the floor, but this height is not required.
AC should be supported every
4½ feet and within 1 foot from boxes and terminations.
FMC should be supported every
4½ feet and within 1 foot from boxes and terminations.
LFMC and LFC should be supported every
4½ feet and within 1 foot from boxes and terminations.
Some home inspectors recommend replacing the entire panelboard and OPDs (fuses and circuit breakers) that are older than about
50 years because the panelboard and the OPD are beyond the end of their service life and may not function properly to protect the house and the occupants.
One fixed in place appliance should not exceed
50% of a general lighting branch circuit amperage rating.
MC should be supported every
6 feet and within 1 foot from boxes and terminations.
Surface-mounted fluorescent fixtures and recessed incandescent, LED, and fluorescent fixtures should not be located within
6 inches from the closet storage areas.
The service equipment, panelboards, and equipment disconnect devices should be located so that circuit breakers, fuse block pulls, and switch handles are not higher than
79 inches above the adjacent walking surface. This requirement applies to all switches including those controlling lights and receptacles. There is no minimum height requirement.
The maximum height of a switch is
79 inches above the floor when the switch is in the up position.
The minimum distance between the lowest individual service drop or service entrance conductor and a roof with a slope less than 4/12 is
8 feet.
One cord-and-plug connected appliance should not exceed
80% of a general lighting branch circuit amperage rating.
The cabinet door for service equipment, panelboards, and equipment disconnect devices should be able to swing open at least
90°.
Light fixtures controlled from two locations require
A 3-way switch in both locations.
EGC (Equipment Grounding Conductor)
A bare or green insulated conductor that provides a ground fault current path (a bonding connection) for equipment with metal cases and parts; these have been installed in most house branch circuit wiring since around 1960.
Branch circuit, multiwire
A branch circuit in which two energized conductors share one neutral conductor; examples can include clothes dryers, ranges and other cooking appliances, and split-wire receptacle circuits; 240 volt water heaters and condensers for air conditioners and heat pumps are not usually multiwire branch circuits.
Enclosure (electrical)
A case or cabinet intended to prevent accidental contact with energized parts; a panelboard is housed inside an enclosure.
Ground fault circuit interrupter (GFCI)
A circuit breaker or receptacle that detects a ground fault by monitoring the imbalance in current flow between the energized and neutral conductors and stops current flow (opens the circuit) when a ground fault is detected.
Grounded
A conductor that is intentionally connected to the earth; this describes what is often called the neutral conductor.
Grounding electrode conductor (GEC)
A conductor that runs between the grounding electrode and an accessible point downstream from where the grounded service entrance conductor connects to the service drop or lateral; the GEC connection is usually at the service equipment.
Lug
A connection point where conductors are inserted and secured; examples include the connection points on panelboards for service entrance and feeder conductors, on terminal bars for neutral and EGCs, and on circuit breakers for branch circuit conductors.
Standards of practice usually require only that the home inspector report the presence or absence of smoke alarms and carbon monoxide alarms.
A few standards require testing these alarms, but this is the exception.
Electrical Nonmetallic Tubing (ENT) is
A flexible corrugated tube designed for routing and protection of conductors and cables. It is usually made from PVC.
Flexible Metal Conduit (FMC) is
A flexible tube made of helically wound interlocking metal designed for routing and protection of conductors and cables.
Joules Law
A formula for calculating heat in an electrical circuit expressed as Heat = Current^2 X Resistance X Time.
Overcurrent protection device (OPD)
A fuse or a circuit breaker; overcurrent protection devices interrupt the flow of electricity when a set current flow is exceeded (an overload), or when a short circuit fault is detected; these devices prevent conductors and devices from overheating and causing fires.
Wiring errors such as reversing polarity at a receptacle or in a device such as a lamp could energize the neutral conductor.
A ground fault condition in improperly bonded metal presents a similar risk.
Conductor
A material, such as copper or aluminum, that permits electricity to flow with low resistance; wires are conductors.
Power
A measure of the work performed by electricity; unit of measure is the Watt.
Dead front cover
A panel that is removed to gain access to the energized components inside an enclosure; the dead front cover is usually behind a door that must be swung or lifted to gain access to the dead front cover.
Subpanel
A panelboard that receives power from an upstream panelboard, usually the main panelboard; also called a downstream or a distribution panel; however, there are no generally accepted terms to identify panels.
A service mast is
A pipe that extends above the roof.
Outlet
A place where current is taken for use; examples include receptacles, light fixtures, and connections at electric appliances such as water heaters.
Modern receptacles are polarized; some older receptacles are not.
A polarized receptacle is one in which a slot is a different size or orientation.
Equipment enclosures may be locked and may be located in a locked room; however, the key should be accessible to
A qualified person. The problem with locked equipment in houses is that the key is often lost or not easily locatable.
Electrical Metallic Tubing (EMT) , sometimes called thin wall, is
A round pipe designed for routing and protection of conductors and cables. It is made from steel or aluminum.
When the service drop conductors are attached to the service mast, the service entrance conductors enter the service mast through
A service head (gooseneck), run inside the service mast, and then run into the meter base.
Type L and Type D fuses have
A short time delay before opening. These fuses are usually more appropriate for general use.
Smoke alarm location requirements for split-level houses can be confusing.
A smoke alarm is required only on the upper level if there is no door between levels, and if the upper level is less than one full story above the lower level. Some jurisdictions require a smoke alarm on each level of a split-level house, and manufacturers usually recommend this as well.
Arc-flash occurs when
A spark jumps between an energized part and a grounded part.
Detached buildings served by 2 or more branch circuits or by feeder conductors to a subpanel require installation of a grounding electrode system.
A subpanel, if installed, should be configured as described next.
Other Solar water Heating system components may include
A temperature/pressure gauge, one or more pressure relief valves or temperature/pressure relief valves, and an expansion tank (if the system uses pressurized transfer fluids). Depending on the system type, a heat exchanger, pump, and a pump controller may be part of the system.
Receptacles in Wet and Damp Areas
A wet area is one exposed to large amounts of liquid water such as an exterior wall that is not protected by a roof. A damp area is one exposed to small amounts of liquid water such as an exterior wall under a roof.
When AC is installed in holes in framing members, measurement is to the edge of the hole.
AC #10 and smaller should be installed through holes in basement floor joists; it should not be attached to the bottom of floor joists.
The AC jacket can serve as the EGC for AC manufactured after 1959.
AC manufactured before that probably can serve as the EGC, but home inspectors should watch for rust and damage that might increase resistance and render the jacket less conductive.
AC may be run exposed, but not where subject to physical damage.
AC should be protected by nail guards when run closer than 1¼ inches to the edge of a framing member such as a stud or a joist.
AFCI protection should be provided by
AFCI circuit breakers.
OPDs and wires generate heat, especially
AFCIs and GFCIs.
Many smoke alarm manufacturers recommend replacing smoke alarms after
About ten years.
This equipment should be readily
Accessible; meaning that one should be able to reach it without climbing over or moving objects or by using portable ladders.
Ionization alarms are more prone to false alarms than are photoelectric alarms.
Alarms that combine ionization and photoelectric sensors in one unit can have higher false alarm rates than single sensor alarms. False alarm rates, by themselves, are a good reason to avoid ionization alarms.
Only 1 grounding electrode is usually required for older houses, however
All accessible grounding electrodes around a house must be bonded together using the same size wire as the grounding electrode wire.
The service equipment is the means to disconnect
All electricity to the house. More common terms include main disconnect, main breaker, and service disconnect.
The problem with the Edison base fuse is that
All fuses have the same size base, so a 20 or a 30 amp fuse can easily be substituted for a 15 amp fuse.
Home inspectors should test 3-way and 4-way switches from
All locations. Sometimes the light will function when a switch is in one position but not when a switch is in a different position.
If the service equipment is in a different cabinet from the main panelboard, the main panelboard is also
Also a Subpanel
Flexible cords may not be
Altered, spliced, or extended.
Anti-oxidant paste is also highly recommended where
Aluminum and copper wires are connected together.
A qualified electrician should perform a service load calculation to determine the amperage load for a house when the house is built, and when a significant increase in amperage load is contemplated.
Amperage load might increase as a result of major remodeling or the addition of new electric appliances such as heat pumps and air conditioners. A similar calculation should be performed for a subpanel before one is added.
Electrocution can occur when the home inspector touches
An energized part and becomes part of the electrical circuit. This risk can be reduced by taking great care when removing and replacing the dead front cover and when inserting your hand or metal objects into the enclosure. Note that home inspectors are not required to insert anything into an electrical enclosure.
Ground fault
An event that occurs when metal that should not conduct electricity (such as a metal water pipe) becomes energized; if the metal is properly bonded, current flow should increase in the circuit and trip the circuit breaker or fuse.
Typical service disconnects involve one or two disconnects in one enclosure.
An exception is an older panelboard design known as the split-bus panel, described later.
A wet area is one exposed to large amounts of liquid water such as
An exterior wall that is not protected by a roof.
A damp area is one exposed to small amounts of liquid water such as
An exterior wall under a roof.
Receptacle
An outlet designed to accept a plug that supplies electricity to an appliance.
The common house electrical service consists of
An overhead service drop or an underground service lateral, a service mast, service entrance conductors, an electric meter in a meter base, the service equipment, feeder conductors, and one or more panelboards. These components are configured in different ways based on the service type (underground or overhead), the age of the house, and local customs. A house may not have all these components.
Because of the tendency of aluminum to oxidize, using
Anti-oxidant paste at terminals is highly recommended.
Light fixtures with exposed incandescent bulbs should not be located
Anywhere in a clothes closet.
IMC and RMC may serve as the EGC when
Appropriate fittings are used.
The jacket covering MC can serve as the equipment grounding conductor (EGC) when
Appropriate fittings are used.
Common sizes for MC used in house wiring are
Around ½ inch diameter.
Unfinished Basement Receptacles
At least one GFCI protected receptacle should be installed in an unfinished basement. This is in addition to receptacles required for appliances such as HVAC.
Garage and Accessory Building Receptacles
At least one GFCI protected receptacle should be installed in each vehicle bay of an attached garage, and in any detached garage if it is provided with electricity.
Laundry Receptacles
At least one GFCI protected receptacle should be installed in the laundry.
Hallway Receptacles
At least one receptacle should be installed in a hallway that is 10 feet or more long when measured along the center of the hallway.
HVAC Service Receptacles
At least one receptacle should be installed within 25 feet from and on the same level as HVAC equipment such as furnaces and condensers.
Smoke alarms should not be installed near combustion sources such as in garages and near combustion equipment such furnaces, boilers, water heaters, and fireplaces of all types.
At least twenty feet of separation is recommended by some manufacturers. Nuisance activation is also common when smoke alarms are installed kitchens, so they should not be installed there.
Every outlet (meaning switch, receptacle, light, and appliance) with solid-conductor aluminum wiring must be repaired.
At up to $60 or more per outlet, this gets expensive. Finding an electrician who can do this may be difficult, at any price.
AC is sometimes called
BX; however, BX is a brand name now owned by General Electric, so only some AC is BX brand. The best description of this wiring method is AC or armored cable.
Solar water Heater Collector types include batch (integral) storage, flat plate, and insulated (evacuated) tube.
Batch collectors consist of a black tank in an insulated box. The water is heated in the tank and stored there until used. Flat plate collectors consist of pipes with black metal fins in an insulated box. Water absorbs heat as it moves through the pipes. Insulated tube collectors consist of glass tubes with metal fins enclosed in an air-sealed outer tubes. Water absorbs heat as it moves through the tubes.
Other places that smoke alarms should not be installed include
Bathrooms and laundry rooms (due to high humidity), near fans and operable windows (air currents could prevent smoke from reaching the sensor), and near florescent lights (electrical interference with the sensor).
Receptacles may not be installed in and above
Bathtubs and Showers.
Switches should not be installed in wet locations inside
Bathtubs and Showers.
If the house electricity system is not connected to the electricity grid, the system may serve most or all of the loads.
Batteries and generators may provide electricity at night and at other times when the system cannot provide enough electricity for the occupant's needs. A wind turbine may be used to supplement a stand-alone PV system.
A home inspector may want to go beyond the minimum standard and test the alarm.
Be careful; testing alarms and reporting the results can be a case where no good deed goes unpunished.
Three-slot grounded receptacles may not
Be ungrounded.
Electricity (Start to Finish)
Begins at a source (e.g., a power plant, a generator, solar photovoltaic panels), flows through an energized conductor (hot wire), performs work at a load (e.g., a light bulb, a range), and returns to the source through a grounded conductor (neutral wire)
One hundred amp and larger cartridge fuses usually have
Blades on both ends.
Any non-conductive contaminants such as paint and rust must be removed at the
Bonding connection point.
Satellite and cable TV coax cable must also be bonded.
Bonding connections at electrical fittings and boxes must be physically secure and provide a low resistance electrical connection.
And while grounding gets more attention,
Bonding is at least as important for electrical safety.
EGCs are really
Bonding wires. They are not part of the grounding system of the house.
Absent or improper handle ties on 240 volt or multiwire branch circuit breakers
Both conductors of these circuits must shut off together; only approved handle ties may be used; wires, nails, and other improvised handle ties are not permitted.
Receptacle and switch boxes should be securely supported.
Boxes supported by conduit should be supported by at least two pieces of conduit. The conduit should be secured within 18 inches of the box.
Switch and receptacle boxes should be securely supported.
Boxes supported by conduit should be supported by at least two pieces of conduit. The conduit should be secured within 18 inches of the box.
Branch circuits not labeled
Branch circuits should be labeled with a permanent marking in sufficient detail to distinguish the branch circuit from other branch circuits; identification by a reference to occupant specific room uses is not acceptable.
The problem with solid-conductor aluminum wiring was that buildings use materials different from that which is found in the electrical transmission and distribution grid.
Buildings have lots of devices like switches, receptacles, and circuit breakers. There are copper wires, such as in light fixtures and appliances, that need to connect to the aluminum wires. The building world was designed for copper wires. Apparently, nobody considered the problems that could occur when you throw aluminum into this copper world.
GFCI protection may be provided either
By GFCI receptacles or circuit breakers, but protection is usually provided by GFCI receptacles because they are less expensive.
The next attempt to fix the problem of terminals on devices that were designed for copper did not work well with aluminum wire was devices labeled
CO/ALR. These devices work and have been required by the NEC since 1981.
Cable installed in crawl spaces is usually not considered subject to physical damage, nor is cable installed away from attic access openings to the attic.
Cable installed within 7 feet vertically and 6 feet horizontally from an attic access opening is considered subject to physical damage.
The following situations may be considered subject to physical damage:
Cable, such as NM, AC, and UF installed under kitchen sinks, and cable within reach on finished walls and in exposed walls including in unfinished walls in basements and garages.
Wiring methods
Cables and raceways approved for distributing electricity from the service point to panelboards and outlets; examples include armored cable, nonmetallic sheathed cable, and various types of conduit and tubing.
Substituting the wrong size fuse
Can allow too much current to flow in the circuit and cause a fire.
Service equipment may be circuit breakers, fuses, or switches that may contain fuses.
Circuit breakers are common in newer houses.
Short circuit faults are detected by the intense magnetic field generated by the short circuit.
Circuit breakers using this technology are called magnetic-trip circuit breakers.
Overcurrent faults are detected by the heat produced by the overcurrent.
Circuit breakers using this technology are called thermal-trip circuit breakers.
The service life of residential depends on the Solar water Heating system type.
Collectors may serve for 20 years or more if properly maintained; direct systems are prone to mineral buildup in the collectors. Mechanical and electronic parts may serve between 5 and 15 years if properly maintained.
LFMC and LFC may be installed in all locations, except those subject to physical damage.
Common locations include exterior HVAC equipment, swimming pools, and hot tubs. They may be buried and embedded in concrete.
AC is a factory-made assembly of insulated conductors in a flexible interlocking metallic covering.
Common sizes used in house wiring are around ½ inch diameter.
AC may not be embedded in
Concrete or installed in conduit and tubing embedded in concrete.
NM may not be embedded in
Concrete or run in conduit and tubing embedded in concrete.
The neutral conductor is a current-carrying
Conductor. Under normal conditions the current is at zero voltage and presents no shock risk, but conditions are not always normal.
Damaged conductors and insulation
Conductors and insulation should be intact; nicked conductors and insulation and multi-strand conductors with absent strands should be cut back to intact material or should be replaced.
Feeder conductors
Conductors from the service equipment or from a panelboard that supply electricity to another panelboard such as a subpanel.
The service drop clearance requirement is to individual conductors, not to
Conductors in conduit and conductors in sheathing. Clearance is not required above openings.
A common defect found inside enclosures is an improper quantity of
Conductors inserted into a lug. This is sometimes called a double tap, especially when done with a circuit breaker.
(NM) serving branch circuits are often run in close proximity to each other and are run in attics that can get hot.
Conductors run in close proximity can get hotter than other conductors as can conductors located in hot places. The lower allowed current provides an extra margin of safety.
Conductors not inserted straight into lugs
Conductors should be installed so that the conductor is substantially straight as it enters a lug; conductors that are substantially skewed may not be securely fastened in the lug.
Branch circuit
Conductors that begin at a circuit breaker or fuse and serve one or more outlets.
When the service drop conductors are attached to the house, the service entrance conductors usually run inside
Conduit or inside the service entrance cable sheathing, then into the meter base.
Water can run down conductors and into the meter base or panelboard cabinet. Water can damage components and increase resistance at
Connections. Increased resistance creates heat and heat creates a fire hazard.
Type S fuse adapters are available for Edison base fuse holders and home inspectors should
Consider recommending that these adapters be installed for safety.
New branch circuits and feeders that serve detached buildings should
Contain an EGC.
Around 1964, somebody had what must have seemed like a good idea at the time.
Copper had become expensive, so why not make solid-conductor building wiring out of aluminum? Aluminum wire had been used for years to transmit and distribute electricity, and had even been used in some building wiring. And so in 1964 they started making solid-conductor aluminum wiring in #8 - 12 AWG nonmetallic sheathed cable intended for residential use.
The cartridge fuse is
Cylinder shaped.
Arcing faults occur when conductors or their insulation are
Damaged and sparks are generated either between conductors or along a conductor.
Light fixtures within the tub or shower perimeter should be listed for
Damp areas, and if shower spray is possible should be listed for wet areas.
Rocker switches are sometimes referred to by the brand name
Decora, which is owned by Lutron. Use of brand names in reports should be avoided.
If installed, the 20 amp, 120 volt branch circuit that serves the kitchen exhaust fan or microwave oven should be a
Dedicated circuit.
Photoelectric alarms are good at
Detecting smoky (smoldering) fires, which is the way many home fires start.
Copper-clad aluminum wire is rated as aluminum wire when
Determining wire ampacity.
A galvanic reaction (electrolysis) occurs when
Different metals are in contact in the presence of moisture. This may cause electricity to flow. This is a good thing, because without it, there would be no batteries.
Electricity flows by two different methods
Direct current and Alternating current
No special grounding and bonding connections are required if the single branch circuit contains an
Equipment grounding conductor (EGC), which it should.
Solar water heating systems can be classified based on the method of heating the water, and on the method of moving the water through the pipes.
Direct systems run the water through a collector and heat the water itself. Direct systems must be shut down and drained when the outside temperature falls below freezing. Indirect systems heat a transfer fluid (one that does not freeze at normal outside temperatures) which in turn heats the water in a heat exchanger. Passive systems rely on convection to move water (hot water rises as it is heated). Active systems use a pump to move water or the transfer fluid.
LFMC may serve as the
EGC when appropriate fittings are used.
Receptacles and switches should be connected to the
EGC, as should the metal box in which they might be installed.
Switches and receptacles should be connected to the
EGC, as should the metal box in which they might be installed.
EMT may be installed in most locations, except those subject to physical damage.
EMT may be buried if it is corrosion protected and is listed for burial.
ENT may be installed in most locations, except those subject to physical damage.
ENT may be installed outside, but only if it is listed for exterior use; all ENT is not listed for exterior use.
At least one GFCI protected receptacle should be located within 3 feet from the outside edge of
Each bathroom sink. The required receptacles may be mounted on the cabinet if the receptacle is not more than 12 inches below the countertop.
Cables and conduit not secured to enclosure
Each cable should enter an enclosure through a cable clamp or within conduit; metal conduit should be connected to the enclosure with a metal fitting or a bonding jumper should be installed.
Knob and tube was most popular from the
Early 1900s to the 1930s. Knob and tube is considered obsolete; however, it may be installed today as an extension of existing knob and tube wiring or by permission from the local building department.
NM is the predominant wiring method in most houses in most markets since the 1940s.
Early versions of NM may be found in houses from the late 1920s to the early 1960s. These early versions had cloth sheathing instead of PVC sheathing.
When MC is installed in holes in framing members, measurement is to the
Edge of the hole.
GFCIs protect people from
Electric shock
Three phase electrical service
Electrical service consisting of three energized conductors and one grounded conductor; this service type is mostly for commercial and industrial buildings.
Single phase electrical service
Electrical service consisting of two energized 120 volt conductors and one grounded conductor; this is by far the most common residential electrical service.
The area directly above and below the enclosure for the service equipment, panelboards, and equipment disconnect devices is reserved for
Electrical system components and should not contain components such as plumbing pipes and HVAC ducts.
Raceway
Enclosed metallic or nonmetallic components designed and listed for holding conductors or cables between points in the electricity distribution system of the house; examples include various types of conduit and tubing.
Damaged enclosure
Enclosures should be intact with all manufacturer approved parts installed and should be free from physical damage; covers and doors should operate smoothly and open at least 90° to allow safe access to interior components.
Exposed metal connected to EGCs and to other bonding means could become
Energized and present a shock risk to anyone who touches the metal.
Another risk reduction technique is to touch the enclosure cover with the back of your hand before opening the door or removing the dead front cover.
Energized conductors can touch the enclosure and screws with pointed tips can penetrate conductor insulation and touch the conductor; both of these can energize the enclosure.
Equipment hidden by decorations such as mirrors and pictures is not usually considered readily accessible.
Equipment blocked by shelves, workbenches, and similar components is not usually considered readily accessible.
Fixed in place appliances should have a means to disconnect electricity to the appliance for the safety of service personnel.
Examples of appliances that usually have a separate disconnecting means include furnaces, boilers, air handlers, air conditioning condensers, electric baseboard heaters, sump pumps, sewage ejector pumps, and swimming pool pumps.
In new homes, at least 75% of the light bulbs should be high-efficacy bulbs.
Examples of these bulbs are: CFLs, LEDs, and fluorescent.
The OPD will allow more current to flow than is considered safe.
Excess current can produce excess heat which can cause a fire.
Electric current produces heat.
Excess current can produce heat beyond the amount that conductors, insulation, and devices in the circuit are designed to tolerate. Excess heat can damage conductors, insulation, and devices. The electrical components can become hot enough to cause nearby combustible materials to ignite, and most houses are built with combustible materials (such as wood). The result can be an electrical fire..0
Enclosures should be large enough to allow sufficient air circulation around OPDs and wires to avoid
Excessive heat buildup that can damage components and cause an electrical fire.
The first rule to updating the electrical system
Existing work does not need to be updated if it complied with rules in effect when installed, and if the system or component is functioning safely.
Ohm's Law and Watt's Law
Expressions of the relationship between current, volt-age, power, and resistance; expressed as Power = Volts X Amps and Resistance = Volts/ Amps.
FMC may be installed in many interior locations, except those subject to physical damage.
FMC may not be buried or embedded in concrete.
Alternating current
Flows back and forth at a frequency of 60 cycles per second (in North American electric power systems). Do not try to envision how alternating current flows, just trust that it does. Alternating current is used in modern utility electrical distribution systems.
Direct current
Flows in one direction from a positive pole to a negative pole. Direct current comes from batteries and from some power supplies used for electronic devices.
Receptacles should be installed so that they are
Flush with or protrude from the cover plate, and so that they do not move when a plug is inserted or removed.
Enclosures installed in wood walls should be
Flush with the wall or should project from the wall. The maximum gap around an enclosure in a finished wall is ⅛ inch.
The allowed current for these conductors is also different if they are used as a service entrance or as a feeder conductor.
For example, #4 copper conductors could be allowed to carry up to 100 amps when used as feeder conductors. One reason for this difference is the assumption that all branch circuits served by a feeder will not be operating simultaneously for a long enough time period to cause the conductor to heat up beyond its safe operating temperature.
The allowed current for #8 and larger copper conductors (#6 and larger aluminum conductors) run in conduit or tubing is different from the value in the previous table.
For example, #8 copper conductors run in conduit could be allowed to carry up to 55 amps when run in conduit or tubing. One reason for this difference is the assumption that nonmetallic sheathed cables
Polarized receptacles help keep metal on devices such as lamps
From becoming energized.
For purposes of grounding and bonding, subpanels include all panelboards downstream
From the service equipment, including the main panelboard if it is a main lug type panelboard. Also included are all outlets, junction boxes, appliance disconnects, and appliances.
The service lateral conductors run
From the transformer into a riser at the house, and then into the meter base. After the meter base, a service lateral system is like a service drop system.
The service drop conductors run
From the transformer on the pole belonging to the utility to a point at the house where they connect to the service entrance conductors (usually with a visible splice). This connection point is called the service point
House panelboard and service equipment enclosures are usually made from steel and some-times from plastic.
Galvanized steel is used if the enclosure is listed for wet or damp area installation. Nonmetal enclosures may be allowed if listed as electrical enclosures.
LFMC is made from
Galvanized steel with a water-resistant PVC outer jacket.
Peak power and continuous power are different.
Generators, especially the portable models, are not intended to operate near peak power for long periods of time.
A common color for PVC is
Gray, but other colors are made.
MC is sometimes called
Greenfield, especially by older electricians, because Green-field cable was an early form of MC.
Like solar PV systems, wind turbine systems are either
Grid-connected or stand alone.
A ground fault occurs when electricity flows in metal (or other conductive material) that is not normally energized.
Ground faults usually occur when a hot wire comes in contact with the conductive material.
EGCs should be connected to separate
Grounding terminal bars. These terminal bars should be connected (bonded) to the subpanel enclosure.
Wind turbine towers are either self-supporting or supported using guy cables.
Guyed towers are less expensive, but require more land to install the guy cables. Some towers can be raised and lowered to allow easier maintenance of the rotor and generator module.
Two circuit breakers may be, and often are, connected with a
Handle tie to protect one 240 volt circuit.
Circuit breakers protecting multiwire branch circuits should be connected with an approved
Handle tie. This is a safety requirement so that both hot legs of the circuit are disconnected simultaneously.
A clothes closet is divided into two storage areas.
Hanging rod storage area and shelf storage area.
Joule's law states that
Heat in an electrical circuit is based on the amount of current flowing, the resistance in the circuit, and time. Increase resistance and heat increases. Heat can cause electrical fires.
Home inspectors should consider reporting when they find an Edison base fuse.
Home inspectors should also report if a penny or similar object is discovered in a fuse holder. Home inspectors should recommend evaluation of the electrical circuits where overfusing has occurred.
Few, if any, alternative energy systems may be legally installed without a permit.
Home inspectors should consider recommending that clients request evidence of a permit and approved inspections when an alternative energy is present.
Many home inspectors test the remote control if it is available.
Home inspectors should report that a fan was not operated if operation is only by remote control and if the remote control was not located.
Generators and all associated components are out of scope of a home inspection.
Home inspectors should report the presence of a generator, and of any related components such as a transfer switch, disclaim inspection, and recommend specialist evaluation to determine the condition and functioning of a generator system.
Alternative energy systems and all associated components are out of scope of a home inspection.
Home inspectors should report the presence of a these systems, and of any related components, disclaim inspection, and recommend specialist evaluation to determine the condition and functioning of the system. Home inspectors who elect to report about these systems should disclose the limitations of their inspection and reporting.
Most of these problematic panelboards are at or past the end of their service life.
Home inspectors should report this end of life condition in addition to defects related to the specific panelboards.
A few older panelboards are known to be, or are suspected to be, problematic.
Home inspectors should watch for these panelboards and make appropriate recommendations. Information about these panelboards is available on the internet and some home inspectors refer clients to websites for more information.
In new construction, at least one carbon monoxide alarm is required in
Houses with a fuel-burning appliance and in houses with an attached garage.
Other alternative (renewable) energy systems include:
Hydroelectricity (electricity generated by water movement), nuclear energy, marine hydrokinetic systems (electricity produced by tides or ocean currents), geothermal (systems using heat from deep within the planet), burning various types of biomass (such as pellets made from wood waste products), hydrogen fuel cells, and algae fuel.
Using Ohm's Law we know that:
I(current in amps) = E(voltage in volts) / R(resistance in ohms). If E=120 volts and R=10 ohms, then 120/10=12 amps. This poorly bonded circuit will carry 12 amps. Twelve amps will not trip a 15 amp circuit breaker, but it is more than enough to kill the rat or anyone else.
IC rated recessed lights should be labeled as such, but the label is usually on the inside of the can.
Identifying an IC rated recessed light from the outside is difficult. Home inspectors may wish to consider whether and how to report recessed lights that are in contact with insulation.
Also in newer houses, 2 grounding electrodes are now required if
If a rod and pipe grounding electrode is used.
The best way to remember bonding requirements is like this:
If it is metal and it is or could be near electrical wires, then it probably needs to be bonded to the grounded wire of the utility.
A receptacle should be located at an island if it measures more than 2 feet long and 1 foot wide.
If the island contains a sink or cooking appliance, the kitchen countertop wall receptacle requirements apply. The required receptacles may be mounted on the cabinet if the receptacle is not more than 12 inches below the countertop and if the countertop does not extend more than 6 inches past the cabinet above the receptacle.
The service equipment is usually located in one enclosure, but it may be in more than one enclosure.
If the service equipment is in separate enclosures, the enclosures should be in one location.
Type W fuses open almost
Immediately when the rated current limit is exceeded. These fuses may be used for general lighting circuits but are inappropriate for circuits serving motors because the fuse may open during the cur-rent surge on normal motor startup.
Voltage will decrease
In a circuit as the resistance increases, given a constant current load.
Some of these recessed lights can allow significant air leakage to occur.
In addition to the energy costs, the heat and air leakage from these lights can contribute to ice dams and can introduce excess moisture into attics. Excess moisture can lead to staining and damage of wood, and to fungal growth.
GFCI devices do not use the EGC to detect a ground fault, so GFCI devices may be installed and will function as intended in circuits without an EGC.
In fact, an approved method of substituting a 3-slot receptacle for a 2-slot receptacle in older houses is to install a GFCI receptacle and label it "NO EQUIPMENT GROUND."
At least one smoke alarm is required on each story including basements and habitable attics, but not including crawl spaces and uninhabitable attics.
In fact, smoke alarms and carbon monoxide alarms should not be installed in crawl spaces and attics because the alarms do not function properly in these dirty and unconditioned environments.
The 240 volt receptacles will be the 4-slot grounded receptacle.
In older houses, some 2-slot receptacles may remain as will 3-slot ungrounded 240 volt receptacles.
The first GFCI requirements (other than for swimming pools) began
In the 1970s for bathroom, garage, and outdoor receptacles. Kitchen countertop receptacles were added in the 1990s and receptacles near laundry room and bar sinks were added in the 2000s.
Copper-clad aluminum wire was produced
In the 1970s. It looks like copper wire except you can see the aluminum wire where the wire is cut.
The materials in an alloy can significantly alter how the metal behaves.
In the case of solid-conductor aluminum wire, the original alloy made the wire brittle and caused a problem called creep.
The first AFCI requirements began
In the early 2000s for circuits serving bedroom receptacles. Requirements for other circuits began in the late 2000s.
AC is limited to interior dry locations, such as
In walls and in masonry cells that are not exposed to dampness or are located below grade.
The switch for exterior lights should be located
Inside the house.
The panelboard label specifies where on the panelboard half-height circuit breakers may be
Installed, and the maximum number of circuit breakers that may be installed on the panelboard.
Enclosures should be listed for use where
Installed. (Enclosures installed outdoors should be listed for outdoor use. This should be indicated on the enclosure label).
IC rated recessed lights may be covered with
Insulation, although this can cause overheating problems that can cause the thermal cutoff switch to activate and shut off the light.
NM is limited to
Interior dry locations, such as in walls, and in masonry cells that are not exposed to dampness and are not below grade.
Exceptions exist that relieve smoke alarm and carbon monoxide hard wiring and interconnection requirements if the work would require disturbing finish surfaces. Interconnection can be accomplished with listed wireless technology.
Interpretation and enforcement of these updating requirements and exceptions varies widely among jurisdictions.
One purpose of Overcurrent Protection Device (OPDs) is to
Interrupt the flow of electricity when excess current is present in the circuit (overcurrent).
One of the reasons for the grounding system
Is to help safely deal with voltage surges.
Where do the electrical system components that are in the scope of a home inspection start?
It begins at the service drop or the visible service lateral and include the service entrance conductors, service equipment, panelboards, enclosures, overcurrent protection devices, grounding and bonding, branch circuit and feeder conductors and associated conduit and tubing, ground fault devices, arc fault devices, and a representative number of receptacles, switches, and lights.
One property of the aluminum alloy used in the original, old technology, solid-conductor aluminum wire is that
It expanded more than copper when the wire got hot. It also expanded at a different rate than the steel device terminals designed for copper.
SE is used as the service entrance conductors between the service point and the service equipment.
It is also used for branch circuits serving large appliances and as feeder cable between panelboards. The neutral conductor must be insulated when used as branch circuit and feeder cable.
The safest and possibly the best solution to solid-conductor aluminum wiring is to rewire the house with copper wire, but clients don't want to hear that.
It is expensive and disruptive, but worth considering.
A newer connector, called AlumiConn, has been available since the early 2000's.
It is much less expensive than the COPALUM connectors and AlumiConn connectors are sold to the public. Selling to the public isn't necessarily a good thing.
Ungrounded 3-slot receptacles are a common defect.
It is not acceptable to install a wire between a receptacle's EGC and neutral terminals. The receptacle tests as grounded when using a 3-light receptacle tester, but it is not grounded. This is sometimes called a bootleg ground, and it is a potential shock hazard because it places electric current into the grounding system.
Anti-oxidant paste is not, however, specifically required by the National Electrical Code (NEC).
It is recommended by some wire manufacturers and is required by some jurisdictions.
While it serves other functions, the grounding system of the house acts like a surge suppressor.
It limits voltage surges in the electrical distribution system of the house and shunts them safely to ground.
PVC may be installed in all locations.
It may be buried and embedded in concrete.
MC may be installed in most locations, except those subject to physical damage.
It may be buried if corrosion protected and listed for burial. It may not be embedded in concrete.
ENT may not be buried, but
It may be embedded in concrete.
Without the grounding system of the house, the energy has no safe path to ground.
It may find an unsafe path, perhaps arcing through branch circuit wire insulation to metal water pipes or gas pipes, or welding the wires in a motor or transformer, or damaging your new plasma TV. Damaged equipment, electrocution, and fires are all possible when voltage surges have no safe path to ground.
SE may be installed in most locations, except
It may not be buried (USE may be buried) and it may not be embedded in concrete. SE may not be run where subject to physical damage.
NM should be supported every 4½ feet and within 1 foot from boxes and terminations.
It should be supported within 8 inches of most plastic boxes.
Flexible cords often supply electricity to
Kitchen appliances.
It is important to note that different dimmers are required for different devices.
LED and florescent lamps, for example, often require a special dimmer designed for each of those lamps. Ceiling fans often require specially designed dimmers as well.
The other problem with cloth-covered NM, shared by most old wiring methods, is
Lack of an EGC. Some home inspectors report the presence of cloth-covered NM, especially if the visible sheathing appears deteriorated.
Areas where a wind turbine may be practical include
Land within a few miles of large bodies of water (oceans, the Great Lakes), elevated land (near tops of mountains and hills higher than surrounding terrain), and in the Midwest, Northeast, and Northwest.
Stranded aluminum wire is available in AWG sizes #8 and larger and is used for
Large appliance branch circuits and for service entrance and feeder wires. This wire has no problems when installed with devices labeled CO/ALR and circuit breakers labeled CU/AL.
Ceiling fans are not light fixtures; they are appliances.
Light fixture rules do not apply to ceiling fans. Ceiling fans place more load on supports because of blade movement, and because some fan blades are not properly balanced.
Light fixture connection to the EGC is almost always concealed during a home inspection and when concealed is out of scope.
Light fixture support is usually concealed.
Panelboards, service equipment, disconnect devices, and similar equipment for residential use are usually required to be inside a
Listed enclosure.
The service equipment location depends on
Local customs and on the age of the house.
Conductors connected to loose receptacles can become loose, arc or overheat, and cause a fire.
Loose receptacles are a common defect, especially receptacles mounted in bathroom mirrors.
EGCs function is to provide a
Low resistance return path for components like metal switch plates and metal equipment cabinets that may become energized.
Low voltage components inside enclosure and conduit
Low voltage components, such as door bell transformers and telephone and coaxial cable, may not be inside enclosures and conduit containing high voltage components unless the low voltage and high voltage components are physically separated by non-conductive guards.
Some lights operate on low voltage, usually 12 or 24 volts.
Low voltage lights are especially common in landscape lighting. Low voltage lighting is out of scope of a home inspection regardless of where the lights are located.
The service amperage is usually the
Lowest amperage rated component starting at the service entrance wires and concluding at the service equipment and the panelboard. For example, if the service entrance wires are 2/0 copper (rated for 200 amps), but the service equipment and panelboard are rated for 150 amps, then the service to the house is 150 amps.
The panelboard is supplied by a
Main breaker on the panelboard or by lugs that supply electricity to all OPDs on the panelboard.
The service life of residential wind turbine rotor/generator modules is reported to be similar to solar PV inverters, between about 5 to 15 years.
Many of these modules are too new to have a meaningful service life record.
Terminal bars
Metal bars associated with a panelboard on which neutral and equipment grounding conductors (EGCs) are mounted; called a neutral bar when neutral conductors or neutral and EGCs are connected; called a ground bar if only EGCs are connected.
Grounding electrode
Metal that is in direct contact with the earth and serves as the electrical system grounding connection; examples include copper-coated steel rods, galvanized steel pipes, water service and well pipes, and reinforcing steel encased in the footings.
AFCI receptacles are allowed only when a circuit is
Modified, extended, or replaced and when installing an AFCI circuit breaker is not practical.
Half-height circuit breakers are often used when
More branch circuits are required than slots are available on the panelboard.
Smaller size wires have
More resistance than larger size wires.
Longer wires have
More resistance than shorter wires
In newer houses, the connection to a water pipe grounding electrode may not occur
More than five feet from where the pipe enters the home.
Most 240 volt circuits are dedicated to serving one electric appliance such as a water heater, an air conditioning condenser, or a well pump.
Most 240 volt circuits serving cooking appliances such as ranges, wall ovens, and cooktops are also dedicated circuits; however, there are exceptions that allow multiple cooking appliances on one circuit.
Single phase 120 volt service to a house is usually considered a reportable deficiency because
Most cooking appliances require 240 volts, and because the electrical current capacity of 120 volt service might not be adequate.
Light fixtures that weigh not more than six pounds may be supported by
Most electrical boxes.
Even 100 amps is often marginal for all but small houses with gas service for heating and clothes drying.
Most newer houses have 150 or 200 amp service and large houses may have up to 400 amp service.
Receptacles installed before NEMA standards may have different slot orientations compared to modern receptacles.
Most of these receptacles have been replaced, but home inspectors may still encounter them.
Some comply with current limitations on allowing air to flow through them between conditioned and unconditioned space.
Most older recessed lights do not comply with current requirements.
The two most common bonding connections are made by
Mounting the terminal bar to the enclosure or by connecting a bar or strap to the terminal bar and connecting that bar or strap to the enclosure.
That is because the grounding system of the house has a minimal impact on clearing ground faults. Two reasons exist for this minimal impact, and they deal with two common electrical myths.
Myth one is that electricity wants to return to ground. It really wants to return to its source, which in the case of most house electrical systems is the transformer belonging to the utility, and ultimately the power generating station. Myth two is that electricity takes the path of least resistance back to its source. It really takes all available paths.
When NM is installed in holes in framing members, measurement is to the edge of the hole.
NM #10 and smaller should be installed through holes in basement floor joists; it should not be attached to the bottom of floor joists.
A flexible cord should not be made from NM or any other permanent wiring method.
NM may not terminate in a plug.
The GEC must be connected to the grounded (neutral) wire of the utility at an accessible location between the load side of the service drop or lateral and the service equipment.
No other grounding connections are permitted downstream from this connection, except for detached buildings supplied from service at another building. This is because additional grounding connections could create unintentional return paths to the source of the electricity.
Excess uninsulated conductor at circuit breaker lug
No uninsulated conductor should extend past the circuit breaker case; this is a possible electric shock hazard.
Neither grounding nor bonding is used during
Normal daily operation of the electrical system of the house.
The nominal capacity of the electric meter or the meter base is usually
Not a consideration when determining service amperage.
All distances are measured to the storage area, and
Not to the shelf or to the rod.
The GEC should be at least #6 AWG copper for 150 amp and greater service.
Number 4 AWG copper wire is required for ufer grounding electrodes with 200 amp and greater service. A number 8 AWG copper wire may be used for 125 amp and smaller services.
Walls above kitchen countertops include
Partial height walls that extend above peninsulas and islands.
Flexible cords may not be used as a substitute for
Permanent wiring.
NM is available in wire gauges from #14 to #2.
Older NM usually has a white jacket for #14 - 10 and a black jacket for larger sizes.
An overhead service drop is common for
Older houses and for houses in rural areas.
Traditional solar panels should function for between 20 and 25 years, although output declines with age.
Older panels are still functioning, and panels over 50 years old have been reported to be functioning. Inverters should function for between 5 and 15 years. The remaining components should function for between 30 and 50 years.
The service equipment for manufactured homes (often incorrectly called mobile homes) is usually located
On a post in the yard near the home. The panelboard in the home should be configured as a subpanel with the neutral conductors isolated from the EGCs.
The ideal smoke alarm location is
On the ceiling at least 4 inches away from the wall.
Wind turbines are not practical everywhere.
One acre or more of land is the recommended the minimum for a wind turbine system. Local zoning regulations should allow a tower 60 feet tall or taller. A 100 foot tall or taller tower is usually recommended for optimal performance.
The general rule for energized and neutral conductors is
One conductor per lug.
Inspecting electrical enclosure interiors presents two safety risks.
One risk is electrocution. The other risk is arc-flash.
Some ceiling fans are operated by remote control.
Operating the fan by remote control is out of scope of a home inspection.
Note that only Federal Pacific Stab-Lok panelboards are involved.
Other types of Federal Pacific panelboards do not have the same alleged defects.
Testing the timer function is
Out of scope for a home inspection.
Burial depth is usually not visible during a home inspection, and is usually
Out of scope.
AC may not be installed
Outdoors, including inside conduit and tubing that is installed outdoors and that is buried. These are considered wet locations.
Fuse
Overcurrent protection device (OPD)
Circuit breaker
Overcurrent protection device (OPD).
Aluminum, like other metals, has a tendency to
Oxidize. Think of oxidation as rust.
PVC conduit is not the same as PVC plumbing pipe.
PVC plumbing pipe may not be substituted for PVC conduit, and PVC conduit may not be substituted for PVC plumbing pipe.
Circuit breaker manufacturer different from panelboard manufacturer
Panel-boards and circuit breakers are made to work as a system; a device from a different manufacturer may not be used even if it seems to fit. Some circuit breaker models from different manufacturers may be substituted for each other. It is out of scope for a home inspector to determine this. The home inspector should recommend electrician evaluation to determine if the correct circuit breakers have been installed.
Alleged defects involve design of the Bulldog Pushmatic circuit breakers, especially circuit breakers from the 1950s and 1960s.
Potential problems include circuit breakers not tripping when they should and circuit breakers energized when showing deenergized.
Alleged defects involve design of the Zinsco/Zinsco-Sylvania panelboard and the circuit breakers.
Potential problems include circuit breakers not tripping when they should, circuit breakers energized when showing deenergized, and arcing at the connection of the circuit breaker with the busbar (not visible unless the circuit breaker is removed).
Alleged defects involve design of the Federal Pacific Stab-Lok panelboard, the enclosure, and the circuit breakers.
Potential problems include circuit breakers not tripping when they should, circuit breakers energized when showing deenergized, and arcing occurring at the connection of the circuit breaker with the busbar (not visible unless the circuit breaker is removed).
Ground Fault Circuit Interrupters (GFCI) circuit breakers and receptacles are intended to
Protect personnel from shock during a ground fault condition.
AFCI circuit breakers and receptacles are intended to
Protect structures from fire caused during an arcing fault condition of the wiring within the wall, the installed switches and outlets, and the equipment plugged in.
Grounding is more about
Protecting electrical equipment
Bonding is more about
Protecting people.
Grounding
Providing an intentional connection to the earth; grounding provides an alternate path for current to return to its source; in an electrical power system, the source is the utility's transformer and ultimately the power plant. See Grounding electrode and Grounding electrode conductor (GEC).
IMC is a thinner wall, lighter weight alternative to
RMC
Foyer Receptacles
Receptacles should be installed in a foyer with an area more than 60 square feet. A receptacle should be installed in each wall space that is at least 3 feet wide and is not interrupted by doors, tall windows, and similar openings.
Recessed lights in new houses should have sealed cans that limit airflow through the light.
Recessed lights in older houses are rarely sealed.
Tabs (twistouts)
Rectangular metal pieces on the dead front cover that are removed before installing a circuit breaker; a tab must be replaced by a filler plate if a tab has been removed and no circuit breaker is installed. See Knockouts.
Wiring method burial depth should be deep enough to
Reduce the chance of accidental damage and the resulting shock hazard that can occur during excavation.
Note that testing a GFCI device disrupts electricity to all downstream receptacles and this can cause problems with certain devices in the house such as refrigerators and freezers.
Remember to check that these appliances are operating before leaving the inspection.
Contact between knob and tube and metal, such as pipes, ducts, foil vapor retarders, and foil radiant barriers is a major
Reportable deficiency.
Oxidation or corrosion on wires (especially on aluminum wires) increases
Resistance at connections such as receptacles and switches.
An aluminum GEC wire may be used, but
Restrictions make it impractical in most cases.
The best description of this wiring method is NM or nonmetallic sheathed cable.
Romex-type may be an acceptable alternative description.
NM is sometimes called
Romex; however, Romex is a brand name owned by Southwire, so all NM is not Romex.
Rigid Polyvinyl Chloride Conduit (PVC) is a
Round pipe designed for routing and protection of conductors and cables.
Home inspectors are not required to test GFCI devices; however, many do.
Some home inspectors test using the TEST button on the device; others test using the test button on their 3-light receptacle tester.
The dead front cover for Federal Pacific Stab-Lok can be difficult to remove and circuit breakers may fall out when the cover is removed.
Some home inspectors will not remove these dead front covers.
The NEC (Article 394.12) does not allow covering knob and tube with thermal insulation in hollow spaces of walls, ceilings, and attics, so thermal insulation-covered knob and tube is a reportable deficiency in most areas.
Some jurisdictions, however, allow thermal insulation-covered knob and tube.
There are two important restrictions when using half-height circuit breakers
Some panelboards do not accept half-height circuit breakers, even if the circuit breaker seems to fit in a panelboard slot. Some panelboards limit the location of half-height circuit breakers to certain slots.
From a home inspection perspective only two recessed light features are important.
Some recessed lights are insulation contact (IC) rated and some are not.
Some solar water heating systems provide hot water for space heating.
Some systems are designed for heating swimming pool water.
Solar water heating systems use solar energy (primarily infrared) increase the temperature of water.
Some systems increase the water temperature to normal domestic hot water temperature and supply hot water directly to the house water distribution system; these are less common. Most systems preheat the water for use in an electric or fuel-fired water heater.
A transfer switch disconnects the house electrical system from the grid and provides electricity to selected branch circuits when the generator is providing electricity.
Some transfer switches perform this function automatically when the generator begins providing electricity; this applies mostly to high-end permanent systems that begin operation automatically when utility electricity ceases. Most transfer switches are manually operated when the occupant engages the generator.
Labels are sometimes faded or have been removed, especially on older fuses.
Sometimes the current rating is labeled inside the fuse or somewhere else on the case.
A few older panelboards are
Split-bus panelboards; so named because electricity for the 15 and 20 amp branch circuits on the lower bus is supplied by a circuit breaker on the upper bus. Split-bus panelboards do not have a main circuit breaker.
Examples of multiwire branch circuits include
Split-wired receptacles that provide the required two 20 amp kitchen countertop receptacle circuits, and split-wired receptacles that are sometimes used to provide electricity to a receptacle serving the dishwasher and the garbage disposer. Clothes dryer and range circuits are also examples.
Knockouts
Stamped openings in an enclosure where conduit or cable clamps are installed to secure conductors or cables. See Tabs (twistouts).
These low-voltage switch systems are specialized and the home inspector should inform the client about this system, and that it may require periodic maintenance because the relays can fail.
Standard hardware store switches will not work as replacements in these systems.
FMC is made from
Steel or aluminum including galvanized steel and stainless steel.
IMC and RMC may be made from
Steel, including galvanized steel, and from aluminum.
NM may be installed exposed, but not where
Subject to physical damage.
The neutral conductors should be isolated from the EGC and from any
Subpanel enclosure.
Remember, panelboards downstream from the service equipment are usually configured as
Subpanels (neutral conductors separated and isolated from the grounding conductors).
All panelboards downstream from the GEC connection are
Subpanels.
Solar photovoltaic (PV) systems use light from the sun to produce direct current (DC) electricity.
Sunlight (photons) strike a silicon-based solar cell inducing an electric current. Each cell produces a small amount of current at low voltage. Cells are assembled into modules which are connected into panels and arrays to produce enough voltage and current to perform useful work at typical voltage and current levels used by modern loads like lights and appliances.
UF may not be used for
Swimming pool, hot tub, and spa wiring because UF's EGC is uninsulated.
Alternative energy systems (also called renewable energy sources) are usually defined as
Systems that provide electricity, heat energy, or energy of motion using means other than combustion of fossil fuels (e.g., oil, gas, coal).
Photoelectric alarms are slightly less responsive than
Than ionization alarms at detecting flaming fires.
The neutral slot is slightly larger
Than the energized slot.
Other wind turbine system requirements include
That a surge protective device (lightning arrestor) should be installed between the wind turbine system and loads served by the house electrical system, and that the tower be connected to a grounding electrode.
The branch circuit serving the condenser should have at least the ampacity shown on the condenser label;
That ampacity should be at least that shown in the following table.
In most houses, the source of electricity is the transformer belonging to the utility and the low resistance return path is the grounded conductor belonging to the utility.
That is why you should find metal water pipe and gas pipe bonding conductors, and the equipment grounding conductors (EGCs) in electrical cable connected to the grounded terminal bar at or before the service equipment. This low resistance return path is essential. Without a low resistance path, enough current may not flow, so that the overcurrent protection device (OPD) clears the ground fault.
Circuit breakers are electro-mechanical devices, meaning
That they have electronic components and mechanical components.
Circuit breakers have been available for house electrical systems since
The 1930s, but were uncommon in many markets until the late 1940s.
Cloth-covered NM can be found in houses from late 1920s, but is more likely to be found in houses built during
The 1940s and 1950s.
These Zinsco/Zinsco-Sylvania panelboards are most common in houses built between
The 1940s and the 1970s.
Circuit breakers have gained substantial market share since
The 1960s and now most houses have circuit breaker-equipped panelboards either from original construction or from updating old fused panelboards.
It gets the derogatory nickname, rag wire, from its cotton or rayon sheathing.
The 1960s saw the cloth sheathing give way to PVC sheathing.
Panelboards using fuses were being installed as late as
The 1960s.
Installation on the wall is acceptable if the top of the case is at least 4 inches and less than 12 inches from the ceiling.
The 4 inch distance helps avoid dead air spots that may prevent smoke from reaching the sensor. Smoke tends to collect near the ceiling so the 12 inch distance helps in-sure that rising smoke reaches the sensor.
Carbon monoxide alarm location restrictions are similar to, but not identical to, smoke alarm restrictions.
The 4 inches from ceiling corner dead air location restriction applies, as do the restrictions involving combustion sources, high humidity, fans and operable windows, and kitchens. The 12 inches to ceiling location restriction does not apply to carbon monoxide alarms. In fact, a lower location on a wall may be advantageous in providing a more rapid response to the presence of carbon monoxide. Just be sure that the alarm is above the reach of children.
Most light fixtures should be connected to
The EGC.
Metal face plates should also be connected to
The EGC. This usually occurs through the screws that attach the face plate to the receptacle or switch.
A home inspector is likely to encounter three types of fuses:
The Edison base (Type T), the Type S base, and the cartridge. Within these types are two sub-types.
Home inspectors should verify the OPD ampacity against the condenser label.
The OPD is frequently not changed when a new, more efficient, condenser is installed. The old OPD ampacity is often too large.
A common defect found when inspecting OPDs is that
The OPD is protecting a conductor that is a smaller size than allowed.
AWG
The abbreviation for American Wire Gauge, a system for identifying the diameter of electrical wires; larger numbers identify smaller diameter wires; #14 (pronounced number 14 or 14 gauge) is the smallest wire used in house wiring, and 4/0 (pronounced four-oh) is usually the largest.
Tin-coated copper wire looks a lot like solid-conductor aluminum wire, but there are some ways to tell the difference.
The age of the house is one way. Houses built before 1964 might contain solid-conductor aluminum wire, but it is unlikely. Another way is to look carefully at where the wire is cut; you can see the copper there. Still another way is to look at the insulation. If the insulation is plastic, it is not tin-coated copper.
In new construction, at least one carbon monoxide alarm is required in houses with a fuel-burning appliance and in houses with an attached garage. Remember that a fireplace is a fuel-burning appliance.
The alarm should be located near the bedrooms and if the bedrooms are widely separated or are on different stories, then multiple alarms are required.
A fuse is a simple device that relies on the fact that the amount of heat produced by the flow of electric current is based on
The amount of current flow, the resistance of the material through which it flows, and time. This is known as Joules Law.
Current
The amount of electricity in a circuit; (similar to water gallons per minute; water flow in a pipe); unit of measure is the Ampere (Amp); expressed as I in Ohm's Law and Watt's Law equations.
The maximum OPD ampacity shown on a condenser label is greater than in the following table to allow for
The brief current surge that occurs when condensers start.
Flexible cords should terminate in a plug that may be inserted into a receptacle, unless
The appliance is listed for use with a flexible cord that may be connected directly to an outlet. Some cooking appliances and furnaces are examples of when direct connection of a flexible cord to an outlet may be acceptable.
A generator will feed electricity into the utility grid system unless the house electrical system is disconnected from the grid.
The backfeeding of electricity into the utility grid is very dangerous to utility workers who are restoring electricity.
Light fixtures that weigh more than fifty pounds should be supported independently from
The box or by a heavy duty box listed for heavy fixtures.
The difference between smoke alarm and carbon monoxide alarm life expectancies makes combining these devices into one problematic.
The carbon monoxide part could fail before the smoke part, rendering the device only partially functional. Combination devices are relatively new, but the home inspector may want to alert the clients to this service life difference for their future maintenance plans.
Knob and tube wiring gets its name from
The ceramic insulators used to support the conductors and from the ceramic tubes used to protect conductors when they ran through framing members.
Service equipment
The circuit breakers, switches, or fuses that shut off electricity to the house; all electricity should be shut off using six or fewer circuit breakers, switches, or fuses; often called the main shutoff or main disconnect.
The main problem with cloth-covered NM is that
The cloth sheathing and the wire insulation deteriorates and becomes brittle with age.
The maximum OPD ampacity and the minimum circuit ampacity for condensers are displayed on
The condenser's label.
The general rule for EGCs is two conductors per lug, if
The conductors are the same size. One reason for this rule is that conductors may slip out of lugs that are not designed for multiple conductors.
Service entrance conductors
The conductors between the service drop or service lateral and the service equipment.
Service drop and service lateral
The conductors between the transformer belonging to the utility and the house; a service drop is above-ground and a service lateral is below ground.
Flexible cords may not be installed inside panelboard enclosures unless
The cord is listed for this purpose (such as a cord for a swimming pool light).
Receptacles should not be located face up on
The countertop.
MC is a factory-made assembly of insulated conductors in a flexible interlocking metallic covering.
The covering may be made from aluminum or steel.
UF is similar to NM in almost all aspects.
The difference is that UF is designed for wet locations and may be buried.
System operation begins when direct current electricity flows from the solar arrays through the DC disconnect switch, which is a service and safety device that allows the arrays to be disconnected from the rest of the system when maintenance is necessary.
The direct current electricity flows into the inverter which converts it into alternating current (AC) electricity that can be used in the house or can be fed back into the utility grid for others to use. The AC disconnect switch is another service and safety device that allows the entire solar system to be disconnected from the house electric system when maintenance is necessary. Electricity from the AC disconnect switch flows into a panelboard of the house electric system through a backfed circuit breaker.
The most common modern 120 volt receptacle is
The duplex receptacle, so called because it can accommodate two plugs. The duplex receptacle is counted as two receptacles.
When ENT is installed in holes in framing members, measurement is to
The edge of the hole.
When FMC is installed in holes in framing members, measurement is to
The edge of the hole.
When LFMC and LFC are installed in holes in framing members, measurement is to
The edge of the hole.
A load controller is a device that allows
The electric utility to temporarily disconnect the electricity to a device during peak demand.
In most cases, light fixtures are mounted on and supported by
The electrical box.
High Voltage (120/240 volt) system
The electrical system of a house, from a home inspection perspective is
Panelboards containing fuses are usually past
The end of their service life, and many have been replaced. Some are still in service, especially in smaller subpanels.
Panel (panelboard, load center)
The equipment on which circuit breakers or fuses are mounted; panels include associated terminal bars; a panelboard is contained in an enclosure; the first and usually the largest panel is often referred to as the main panel or the service panel; however, there are no generally accepted terms to identify panels.
The problems with the COPALUM connector include
The fact that it is expensive, partly because the materials and tools are proprietary, and because electricians must be trained to use them.
Service drop conductors may be attached to the house on
The fascia or on the wall.
Two AFCI types exist.
The first type was the branch circuit/feeder. These devices detected arcing faults between conductors (parallel faults). These devices have not been permitted in new installations since the late 2000s. The present type is the combination type. These devices detect both parallel faults and faults along a conductor (series faults).
Modern NM is a factory-made assembly of insulated conductors and a typically uninsulated EGC.
The flexible nonmetallic covering is made from PVC.
SE is a factory-made assembly of insulated conductors and a typically uninsulated EGC.
The flexible nonmetallic covering is made from PVC.
The hanging rod storage area extends vertically from
The floor to the highest rod or 6 feet, whichever is higher, and horizontally 2 feet from the walls.
Flat NM should be stapled with the flat side toward
The framing member.
Modern molded case circuit breakers come in three case styles.
The full-height (1 inch) case and the half-height (½ inch) case styles protect one 120 volt circuit. The tandem case style protects one 240 volt circuit.
A wall switch-controlled permanent ceiling or wall fixture should be located in every hallway, interior and exterior stairway, attached garage, detached garage where electricity is supplied, and at exterior doors.
The garage vehicle door is not considered an exterior door.
A transfer switch is required to disconnect the house from
The grid while the generator is providing electricity to the house.
The low resistance return path is
The grounded conductor belonging to the utility.
You should find metal water pipe and gas pipe bonding conductors, and the equipment grounding conductors (EGCs) in electrical cable connected to
The grounded terminal bar at or before the service equipment.
The EGC should be connected to
The grounding electrode.
Bus (buss, busbar)
The heavy, rigid metal part of a panelboard on which circuit breakers or fuses are mounted; sometimes used to describe metal terminals to which the neutral and equipment grounding conductors (EGCs) are connected.
The shelf storage area extends vertically from
The highest shelf to the ceiling, and horizontally from the widest shelf or 12 inches from the wall, whichever is larger.
Home inspection standards of practice require home inspectors to inspect the interiors of electrical enclosures, if
The home inspector believes that it is safe to do so.
A home inspector is not required to inspect electrical enclosure interiors, or perform any other inspection procedure, if
The home inspector believes that there is a risk to the home inspector, to others, or to the property.
When the home inspector tests an alarm by pressing the test button, the home inspector may only be testing the sound producing device.
The home inspector may not be testing the alarm's sensor. There are UL listed aerosol smoke products for testing smoke sensors, but such testing is out of scope for a home inspection.
Each unit of a two-family house or a townhouse may have as little as a 60 amp service; however,
The home inspector may wish to report such a limited service to the client.
Interior stairway lights should be capable of lighting all treads and landings, including the top and bottom landings.
The home inspector should be aware of how the stairway and landings will be illuminated at night, including shadows and unsafe lighting.
FMC is a type of conduit.
The individual conductors or cables pulled in FMC are not paper wrapped either. None of this is usually visible during a home inspection.
Wiring method bends should not damage the component.
The internal diameter of conduit and tubing should not be reduced.
Most small portable generators are gasoline-powered; some are powered by propane.
The large permanent generators are usually powered by natural gas, propane, or diesel.
A wall switch-controlled light should be located in every habitable room and bathroom.
The light fixture should be a permanent ceiling or a wall fixture in kitchens and bathrooms. The light fixture may be controlled by a switched receptacle in other rooms.
Examples of detached buildings include storage and work sheds, barns, and guest houses if electricity to the guest house is supplied from
The main house.
The quantity of conductors that may be inserted into a lug is determined by
The manufacturer's instructions for the device.
Ampacity
The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.
One type of panelboard enclosure is often called a meter-main enclosure because
The meter base, service equipment, and the panelboard are located in one enclosure, with the meter base in one section and the service equipment and panelboard in the other section.
There are two types of smoke alarms.
The most common type is the ionization alarm. The less common type is the photoelectric alarm.
There are two ways to deal with this situation if the branch circuit does not have an EGC.
The most common way is to install a GFCI receptacle and label it "NO EQUIPMENT GROUND." The other way is to install an EGC to the nearest available EGC from another branch circuit, or to an EGC in the nearest panelboard.
Modern polarized 120 volt receptacles have:
The neutral slot on the left. The energized slot on the right The equipment grounding slot on the bottom (when installed in the typical grounding slot down position).
The modern 240 volt receptacle has:
The neutral slot on top The two energized slots on the sides The equipment grounding slot on the bottom (when installed in the typical grounding slot down position).
All tin-coated copper wire is near the end of its expected service life.
The old rubber insulation can crack and fail, especially when disturbed.
Note that new requirements in NEC 2014 include that receptacles in an attached garage should be on a dedicated circuit.
The one receptacle for each vehicle bay is also a new requirement. Older houses will usually not comply with this new requirement, and non-compliance is not a defect.
There are no specific limits on the number of receptacles on a general lighting and receptacle branch circuit in houses.
The only requirement is to evenly distribute the load among these branch circuits.
AC can be difficult to distinguish from metal-clad cable (MC) and flexible metal conduit (FMC).
The outer jacket of AC is usually interlocking metal. The outer jacket of MC may be interlocking metal, or it may be smooth or corrugated metal. Conductors in AC are wrapped in paper; conductors in MC are not. AC should have an anti-short bushing at termination points; this is not required for MC, although some electricians install them anyway.
The fuse or circuit breaker at a panelboard is always an acceptable disconnecting means if
The panelboard is in sight of the appliance.
Another type of panelboard enclosure is often called a main lug panelboard enclosure because
The panelboard is served by feeder conductors from the service equipment or from another panelboard. Main lug panelboards are usually configured as subpanels, even if the panelboard is the service panel for the house.
Too many circuit breakers on panelboard/half-height circuit breakers in wrong slots
The panelboard label states how many branch circuits the panel may serve and which slots, if any, may contain half-height circuit breakers.
Panelboard ampacity more than service entrance or feeder conductor ampacity
The panelboard label states the minimum ampacity of the supply conductors that should serve the panelboard; the conductors may be larger than the minimum capacity, but not smaller.
In newer houses, the connection to a water pipe grounding electrode may not occur more than five feet from where
The pipe enters the home.
Service point
The place where the service drop or service lateral conductors end and the house service entrance conductors begin; this is usually at the drip loops for service drops; the service point for service laterals is more difficult to distinguish, but is often at the meter.
Generators are either small portable models or large permanently installed models.
The portable models usually produce between 3,000 and 10,000 watts peak power and are intended to provide power for essential systems such as heat, a well pump, and refrigeration. The permanently installed models usually produce from 7,000 to over 22,000 watts peak power and are intended to provide power for most or all of the occupant's electricity use.
Voltage
The pressure of electricity in a circuit, similar to water pressure in a pipe; unit of measure is the Volt.
Bonding
The process of connecting, both physically and electrically, metal components of the electrical system that are not intended to carry electrical current to provide a low resistance return path to the circuit breaker or fuse to clear ground faults; bonding is an electrical safety system.
Resistance
The property of a material to allow or restrict the flow of electricity; materials with low resistance are conductors and materials with high resistance are insulators; unit of measure is the Ohm.
When the service equipment is a single overcurrent device
The rating on the service equipment overcurrent device is usually the service amperage, but not always.
When the tab between the receptacles is removed
The receptacle can be served by two different branch circuits, or half of the receptacle can be switched and the other half can be permanently energized.
Do not use a smoke pen or other unlisted smoke generating device to test a smoke alarm.
The result could be inaccurate, and the home inspector could damage the alarm.
Note that the grounded (neutral) wire and the EGC are connected in the distribution panelboard in the following illustration.
The result is that current is flowing on all bonded metal and on the EGC, as indicated by the yellow triangles. While this current is at zero volts (thus no power) under normal conditions, there are situations when this current could be at positive voltage, and could create a hazard to both people and equipment.
A modern wind turbine functions by capturing wind energy using a rotor (blades similar to an airplane propeller) which rotates a shaft which is connected to an electric generator.
The rotor and generator are mounted on a tower that is tall enough so that the rotor blades are at least 30 feet above obstructions such as buildings and trees within 300 feet. System electrical output can range from 20 watts to 30,000 watts or more, depending on wind speed and generator capacity.
Wind turbine systems have similar types of components and requirements as a solar PV system.
The rotor and generator module, previously discussed, takes the place of the solar arrays.
Home inspectors are required by most standards of practice to report
The service amperage to the house.
Another type of panelboard enclosure is often called a main breaker panelboard enclosure because
The service equipment and the panelboard are located in one enclosure.
Determining service amperage can be easy when
The service equipment is a single overcurrent device; the rating on the service equipment overcurrent device is usually the service amperage, but not always.
The grounding electrode conductor (GEC) usually connects to the electrical system at
The service equipment.
The service entrance conductors then run from the meter base to
The service equipment.
Service entrance conductors should form drip loops below
The service head so that water drains off the conductors before the conductors enter the service head. The service head should be angled down so that water does not enter through it.
The upper bus has slots for five 240 volt branch circuits and one 240 volt circuit breaker that serves the lower bus.
The six device service equipment limit is satisfied by shutting off the upper bus circuit breakers.
The IRC requires updating smoke alarms and carbon monoxide alarms to current standards when work requiring a permit is performed.
The smoke alarm update exceptions involve exterior work such as roof coverings and wall claddings, and work involving only plumbing and mechanical systems.
Existing branch circuits and feeders that serve detached buildings and do not contain an EGC may remain; however, a grounding electrode should be installed if one is not present.
The subpanel should be configured as a main breaker panel. EGCs and neutral conductors may be connected to the same terminal bars. Both EGCs and neutral conductors should be connected to the grounding electrode and bonded to the enclosure.
Basements, attics, and crawl spaces should have at least one light if the space is used for storage, or if it contains equipment that requires service.
The switch should be near the entrance to the space. The light may be located anywhere in the space except the light should be near the equipment, if any. The light may be a pull chain type if the light is located near the entrance to the space.
The term subject to physical damage is often used regarding electrical components.
The term is undefined, and as such is subject to interpretation.
Most exterior stairways should have a light near
The top landing.
In most houses, the source of electricity is
The transformer belonging to the utility
Two types of PV systems exist.
The two types are grid-connected (also called grid-tied and utility-interactive) and stand-alone. Within these two types are several possible configurations.
It is usually not possible to identify the smoke alarm type by looking at it from below.
The type is usually on the back and requires removing the alarm from its mounting bracket to identify its type.
Electricity leaves the house through
The uninsulated grounded conductor.
Grid-connected systems are connected to
The utility electricity grid and are intended to provide some or all of the occupant's electricity needs during daylight. The occupants rely on the utility to provide electricity in excess of the system's capacity, on cloudy days, and at night.
Some service equipment is located inside and some service equipment is located outside.
There is no benefit to either location.
The service equipment may be in one or more separate cabinets, or it may be in the same cabinet as the main panelboard.
There is no benefit to either location.
Water heater and air conditioning condenser circuits are usually not multiwire branch circuits because
There is no neutral (ungrounded) wire in the circuit.
Modern circuit breakers for house electrical systems are called
Thermal-magnetic-trip circuit breakers.
Light fixtures that weigh more than six pounds should be supported by a box listed for support of heavier light fixtures.
These boxes should be secured directly to framing or should be secured to metal bars that are secured to framing.
Boxes used to support ceiling fans should be labeled as suitable for ceiling fans.
These boxes should be secured directly to framing or should be secured to metal bars that are secured to framing. Ceiling fan support is usually concealed.
The most common exception is some 15, 20, and 30 amp circuit breakers manufactured by Square D and sometimes sold under the brand name Homeline.
These circuit breakers have a double saddle under the lug screw that accepts two conductors of the same size.
Receptacles installed in wet areas should have a cover that is weatherproof when a plug is inserted.
These covers are sometimes called bubble covers.
Receptacles installed in damp areas should have a cover that is weatherproof when a plug is not inserted.
These covers have a cap that snaps shut over the receptacle when the receptacle is not in use.
Switches installed in wet and damp areas should have a cover that is weatherproof.
These covers have a cap that snaps shut over the switch.
A separate disconnecting means should be installed if the panelboard is not within sight of the appliance.
These disconnecting means usually consist of a switch, a fuse block, or a pull tab inside an enclosure located near the appliance.
Several other switch types are available.
These include multiple switches in one device and a switch and a receptacle in one device for installation where space is insufficient for individual switches.
Some houses built in the 1960s and 1970s have low-voltage switches that activate 120 volt light fixtures.
These low-voltage switches connect to an enclosure full of relays located in the attic, or sometimes in the garage.
Modern circuit breakers used in house electrical systems are molded case circuit breakers.
These modern circuit breakers use two technologies to detect and clear two different types of electrical faults.
At least one GFCI protected receptacle should be installed in any accessory building that is provided with electricity.
These receptacles are in addition to receptacles required for appliances such as HVAC and laundry appliances.
Situations sometimes occur when it is not possible to determine the service amperage.
These situations occur most often when there are multiple service equipment disconnects in multiple enclosures.
Toggle switches containing mercury were popular in the 1960s and 1970s
These switches can be identified by their silent operation. These switches are considered hazardous waste.
Programmable switches and timer switches are available.
These switches usually have a manual override that allows the home inspector to test operation of the light fixture.
Many, if not most, metals we use every day are not pure forms of the metal.
They are a combination materials called an alloy.
GFCIs and AFCIs have similar names, but
They are completely different devices that provide protection against different risks.
These panelboards sometimes have the logo FPE on the enclosure and are also known as Federal Electric and Challenger.
They are most common in houses built between the mid-1950s and the early 1980s.
The service drop conductors may be attached to the house OR
They may be attached to a service mast.
IMC and RMC may be installed in all locations.
They may be buried and embedded in concrete if corrosion protected and listed for the location.
Generators are usually intended to provide electricity to the house if the utility electricity is interrupted.
They may provide all or some of the electricity to off-the-grid houses.
Stand-alone solar systems are not connected to the utility grid.
They may provide electricity to one or a few loads.
Receptacles may not be more than 66 inches above the floor if
They serve as a required receptacle.
Exterior receptacles should be installed where
They will not be subject to flowing water, but no minimum height is specified.
Multiple conductors in one lug may not be protected by an OPD or may be overfused.
This can be an especially dangerous defect.
Contaminants such as paint and drywall joint compound in the enclosure
This could increase resistance and cause an electrical fire.
Do not be confused by the term combination AFCI.
This device protects against two types of arc faults. An AFCI does not combine a GFCI and AFCI into one device.
Switches should be installed so that ON is in the up position.
This does not apply to 3-way and 4-way switches and to switches normally operated horizontally or by rotation.
The service equipment, panelboards, and equipment disconnect devices, such as for furnaces and condensers, should be located where access is safe, and should be provided with a safe space around them for inspection and repair.
This equipment should not be located in storage spaces, clothes closets, bathrooms, and above stair steps. Stair landings are an acceptable location if the working clearances are available. Indoor equipment should have an electric light nearby.
Short circuit
This event occurs when current flows between conductors in an unintended manner, such as between the hot and neutral conductors.
Toxic or flammable transfer liquids and gasses may not be used as the heat transfer medium.
This includes ethylene glycol (automobile antifreeze).
Flexible cords may not be installed within or through walls, ceilings, and floors.
This includes suspended and drop ceilings.
Melted insulation and charred conductors
This indicates a loose connection at the lug or overcurrent that was not interrupted by the OPD.
An old panelboard is sometimes replaced by a new panelboard and service equipment with a greater amperage rating, but the service entrance wires are not replaced.
This is a dangerous situation because the higher amperage equipment can allow more current to flow through the service entrance wires than the wires can safely handle. Insulation can melt and an electrical fire can start.
Absent tabs and knockouts
This is an electrical shock hazard; tabs and knockouts must be replaced with material similar to the original; tape, cardboard, and similar improvised materials are not permitted.
Rust
This is an indication of a possible water leak into the enclosure; this could increase resistance and cause an electrical fire.
Receptacles serving walls in habitable rooms should be spaced so that no point along the wall is more than 6 feet from a receptacle.
This means receptacles are often spaced about every 12 feet.
"A grounding connection shall not be made to any grounded circuit conductor on the load side of the service disconnecting means, except as provided in Section E3607.3.2."
This means that neutral conductors must be isolated from any equipment grounding conductors (EGCs) and other bonded metal at all points past the service equipment.
What about replacing all the switches and receptacles with CO/ALR devices?
This might help the situation with aluminum wire made after 1972, but this solution doesn't address the creep problem of old technology aluminum wire. This solution also does not address other aluminum wire terminations such as light outlets.
Home inspectors may wish to consider reporting very heavy light fixtures and recommending evaluation if support cannot be confirmed.
This situation is uncommon.
There should be a switch near the top and bottom landings if there are six or more risers.
This switch should be a 3-way or 4-way switch so that the light can be controlled at the top and bottom of the stairway.
The general rule regarding the allowed branch circuit conductor ampacity is contained in the following table.
This table does not apply to conductors serving air conditioning and heat pump condensers.
Most solar photovoltaic (PV) systems use traditional solar cell panels.
This technology has been available for over fifty years. Newer thin film technology allows solar cells to be integrated into building materials such as roof coverings.
Another solution to solid-conductor aluminum wiring is the COPALUM connector.
This uses a patented connector and crimping tool to cold weld copper wire to aluminum wire.
Metal face plates should also be connected to the EGC.
This usually occurs through the screws that attach the face plate to the receptacle or switch.
Electricity service is sometimes referred to as 220 volts.
This voltage is not supplied by modern electric utilities.
One problem with aluminum expanding more than copper when the wire gets hot was that expansion and contraction caused the wire to work loose at connections.
This was especially true for receptacles and switches connected from the back instead of using the side screws. Loose connections equal higher resistance and arcing.
Light fixtures should be securely attached to whatever mounting components are used, and
Those mounting components should be securely attached to framing.
There are currently about nineteen different NEMA standard receptacle types that might be found in a house, excluding
Those used in 3-phase electrical service.
Three phase electricity has
Three energized conductors
Think of each phase as a television channel.
Three phase electricity has three channels and single phase electricity has one channel. Three phase electricity has more potential power than single phase electricity, but not three times more.
The alarm will not activate if the sensor is not functioning and pressing the test button may not test the sensor.
Thus, pressing the test button does not insure that the alarm will function as intended under actual fire or carbon monoxide conditions. It is critical that the home inspector inform the clients about this distinction if home inspector tests the smoke alarms and carbon monoxide alarms and reports the test results.
An underground service lateral is common for newer houses and is more desirable because the conductors are less likely
To be damaged.
The other purpose of OPDs is
To interrupt the flow of electricity when a short circuit occurs.
Early switches included various types of rotary switches (1920s and before), push button switches (1920s-1940s), pull chain switches, and toggle switches (1930s to present).
Toggle switches are the ancestors of the modern snap switch, the type with a small handle.
Track lights should be installed according to manufacturer's instructions using parts made for use with the track lighting system.
Track lights should not be installed in wet or damp locations, where they could be subject to physical damage, and through walls.
Single phase electricity has
Two energized conductors.
The electricity enters the house through
Two insulated energized conductors with 120 volts on each conductor.
NM is commonly described using
Two numbers separated by a slash or a dash, such as 14/2 or 14-2. The first number is the wire gauge and the second number is the quantity of insulated conductors. One EGC is included but may not be specified.
Cable
Two or more conductors encased in sheathing; examples include non-metallic sheathed cable (often referred to by the brand name Romex) and armored cable (often referred to by the brand name BX).
The substitution problem caused by Edison base fuses was corrected by the
Type S base fuse. Each Type S fuse has a different size base, so one size cannot be substituted for another.
The usual burial depths are:
UF and MC: 24 inches, RMC and IMC: 6 inches, PVC, LFMC, and LFC: 18 inches.
Unbalanced blades can cause the fan to wobble and place more load on the box and other connections.
Unbalanced ceiling fans are a reportable defect.
Covering knob and tube with thermal insulation is a bad idea, but not for the reason many believe.
Under normal operating conditions, knob and tube covered by thermal insulation should not overheat more than any other wiring method. Thermal insulation-covered knob and tube may be damaged by attic traffic. Carelessly installed thermal insulation may push the wires too close to framing and other surfaces.
A GFCI protected receptacle should be installed within 78 inches vertically from a deck, balcony, or porch that is
accessible from inside the house; this receptacle is addition to the required at-grade receptacle.
Electricity is generated
as three phase, and is converted to single phase for almost all residential electrical systems.
Panelboards are limited to a fixed number of
branch breakers.
UF may not be embedded in concrete, but
it may be installed in conduit and tubing embedded in concrete. The jacket covering UF is usually gray.
Although Thomas Edison patented an early version of the circuit breaker in the late 1800s, the fuse was the primary OPD in houses through
much of the 1950s.
In newer houses, metal water service pipe may
not be the only grounding electrode, but if it is present, it must be bonded to all other grounding electrodes.
At least one GFCI protected receptacle should be installed within 78 inches vertically from
the walking surface (grade) at both the front and rear of the house.
One characteristic of houses built when knob and tube was popular was a lack of (or minimal)
thermal insulation.
Common sizes for IMC and RMC range from
½ to 4 inches diameter.
Common sizes for EMT range from
½ to 4 inches in diameter, and it comes in 10 foot sections.
Solar water heating system components include:
• A collector, • A storage tank (may be the collector in a batch system), • Insulated pipes, • A temperature limitation system to limit the temperature of fluids entering or exchanging heat with a pressurized vessel inside the building to not more than 180° F, • Valves to isolate the solar water heating system from the rest of the domestic hot water system, • A backflow preventer, • Labels as required by local standards.
Other components of a PV system include:
• Conduit, electrical metallic tubing (EMT) and metal-clad cable (MC) are common, but other types of conduit and tubing may be acceptable if listed for use where installed; conductors should be run in conduit except where entering or leaving equipment or when necessary to allow movement of an array, • Conductors, may be single conductors or multiple conductor cables if listed for use where installed, • Mounting hardware appropriate for the modules installed, • Waterproofing components where components penetrate roofs and walls.
Common light fixture types include:
• Flush-mounted ceiling fixtures that are installed flush against the ceiling • Hanging fixtures (e.g., chandeliers and pendants) that hang from the ceiling by a chain, rod, or cord • Wall-mounted fixtures (sometimes called sconces) • Recessed fixtures (sometimes called can, high-hat, or pot lights) that are installed into holes in the ceiling • Track lights that are installed in a metal strip that is usually attached to the ceiling • Various types of under-cabinet fixtures that are usually for task lighting of kitchen countertops • Other specialty light fixtures, such as cable lights, are also available.
Areas where GFCI protection for receptacles is now required are usually where water may be present and include:
• Kitchen countertops, • Bathrooms, • Garages, • Laundry rooms, • Unfinished basements, • Unfinished detached buildings, • Crawl spaces, • Outdoors. • GFCI protection is also required for the circuit serving the dishwashing machine (NEC 2014).
Other PV system requirements include:
• PV conductors should be identified as such where accessible • PV conductors should not be installed in the same conduit or tubing as conductors from other systems, except where the PV conductors connect to other systems • Conduit, tubing, and boxes containing PV conductors should be labeled as such, this is a newer requirement so older systems may not comply • Exposed non-current-carrying metal parts of the PV system should be grounded • At least two 36 inch wide pathways should be provided on separate roof planes for access by emergency personnel, at least one of these should be on the street side, this is a new requirement so most systems will not comply • Arrays should be set back from a roof ridge either 18 or 36 inches depending on how much of the roof area is occupied by arrays, this is a new requirement so most systems will not comply.
The most common alternative energy systems likely to be found at residential structures include:
• Solar photovoltaic (PV), • Wind turbines, • Solar water heating, • Passive solar design, • Ground-source heat pumps (commonly but inaccurately called geothermal systems), • Water-source heat pumps.
Light bulbs (lamps) come in five common types.
• Thomas Edison invented the incandescent bulb, so it has been around since the beginning. Incandescent bulbs are inefficient, and are being phased out by law. • Compact fluorescent bulbs (CFLs) are one new type of energy efficient bulb. Complaints about CFLs include that some take time to emit the full light output and that they contain mercury, a hazardous material. • Light emitting diode bulbs (LEDs) are another energy efficient bulb. The primary complaint about LEDs is high cost; however, cost is decreasing and these bulbs are said to last for up to twenty years. • Fluorescent bulbs have also been around for a long time. They are usually straight tubes, but are available in U and circular shapes. Fluorescent bulbs require a burst of energy from a component called a ballast to start working. The primary complaint about fluorescent bulbs is what some consider the harsh or unnatural light. • Halogen bulbs are similar to incandescent bulbs, but are more energy efficient. Halogen bulbs can produce significant heat and can burn out quickly in light fixtures that cannot dissipate the heat. Halogen bulbs usually require a special socket, so only a Halogen bulb may be used in the fixture.
Required individual branch circuits include:
• Two-20 amp, 120 volt branch circuits that serve only kitchen countertop receptacles and receptacles in the breakfast and dining rooms; one of these circuits may serve the refrigerator, • 120 or 240 volt branch circuits that serve only one furnace or air handler, • a 20 amp, 120 volt branch circuit that serves only receptacles in the laundry room, • One-20 amp, 120 volt branch circuit to serve only receptacles in bathrooms (exception: one 20 amp, 120 volt branch circuit for each bathroom may serve both lights and receptacles in the bathroom).
Components that may require bonding include metal:
• Water and gas distribution pipes • Electrical conduit • Electrical equipment cabinets and cases • Framing and sheathing • HVAC ducts • All metal parts of the electrical service and distribution systems.
The maximum gap around an enclosure in a finished wall is
⅛ inch.
Common sizes for LFMC and LFC range from
⅜ to 4 inches diameter.