Unit 7 Electrical Systems

The service box can be inside, outside, or in the garage. True or False?

True

The service box may stand alone or be combined with the distribution panel?

True

The wire size for the service drop must be the same as the wire size for the service entrance conductors.

False

There can be up to 10 throws to disconnect all the electricity in the house?

False

You are allowed to ground to the gas piping.

False

The drip loop is typically part of the service drop.

False

Typical distribution panels have 60 circuits.

False

List 16 conditions that may be found in all panels.

obsolete and/ or fused neutrals, damaged panel or components, loose panel, inappropriate support materials, loose or missing door, opening in panel, panel too small, overheating, rust or water in panel, circuits not labeled, panel crowded, poor access, installed upside down, not suitable for aluminum wiring, poor location and, outdoor panel not weathertight.

What is the problem with running wire across the top of the attic ceiling joists?

Someone might get electrocuted/ They are visible and wire could be stepped on.

Which of the following is a safety issue?

(b) The main fuses have a higher rating than the service entrance wire

Wire should be __________ inches away from the edge of studs.

11/4 inches away from the face of studs or joists.

List two different branch-wire materials you might see.

1. Copper 2. Aluminum

List 17 common branch circuit-wire problems?

1. Damaged 2. Not well secured 3. Loose connections 4. Open Splices 5. Wires too close to ducts, pipes, vents, chimneys, and flues 6. Wires too close to the edge of studs or joists 7. Wires run through steel studs without protection 8. Exposed wires on walls or ceilings 9. Exposed wires in attics 10. Wire under carpets 11. Indoor cable used outdoor 12. Buried cable used outdoors 13. Overhead wires not stranded 14. Household wiring used as extension cord used as permanent wiring 15. Undersized wire 16. Improper color coding 17. Abandoned wire

Describe three different cable types you might see?

1. NM Cable (Romex or Loomex) 2. UF BX (underground feeder) (or A-90 cable) 3. Knob and tube

List 11 common problems with service entrance conductors.

1. No drip loop 2. No masthead (entrance cap, service cap. pothead, weather head) 3. Masthead not weathertight 4. Service entrance wires too close to the roof 5. Wires too close to the roof 6. Mast or conduit rusted 7. Mast or conduit bent 8. Mast rotted (if wood) 9. Mast, conduit, or cable not well secured 10. Mast, conduit, or cable not weathertight 11. Conduit or cable not well sealed at house wall penetration 12. Cable frayed, mechanically damaged, or covered by siding

List 13 common problems found with grounding systems.

1. No grounding 2. Grounding wire attached to plastic pipe 3. Ground wire after (downstream of) meters and valves, with no jumper 4. Spliced ground wire 5. ground wire attached to abandoned pipe 6. Poor connections 7. Ground connections not accessible 8. Ground rod cut off 9. Corroded ground wire 10. Undersized ground wire 11. Neutral bonded to ground wire after (downstream of) service box 12. Neutral wires not bonded to ground wire at service box 13. Service box not bonded to ground wire 14. No ground in subpanel feeder wires

Which of the following is a safety concern?

B. A fuse that is too big

What is meant by linking in multiwire branch circuits?

Linking means that the fuses or breakers for multiwire branch circuits have to be shut in pairs.

Is the service drop overhead or underground?

Overhead wires

List six problems found with wires in panels.

1. Sheathing not removed 2. Overheating 3. Loose connections 4. Loose connections 5. Damaged 6. Not well secured 7. Wires crossing bus bars 8. Abandoned wires in the panel

List five common areas of water penetration into service entrances.

1. house entry 2. joints in conduits 3. the service cap (masthead), 4. the flashing at the roof level, and 5. the meter base

List four common problems found with only with breakers?

1. multi-problems include 2. too many breakers 3. wrong breaker in panel and 4. loose breakers

List six destinations where ground wires can terminate?

1. through metal water supply pipes 2. through metal rods driven into the ground 3. through wires (often 1/2 inch reinforcing bar) buried in the footing of the building (UFER grounding); and 4. buried grounding plates and rings; 5. the frames of metal building (more common in commercial than residential construction) and; 6. the metal casings of private water supply wells

Lis four common problems with knob and tube wiring?

1.Connections not in boxes 2. Brittle wire, insulation, or sheathing 3. Wire buried in insulation 4. Fused neutrals

List nine common problems with service drops?

1.Overhead wires too low 2. Overhead wires too high 3. Damaged or frayed wires 4. Trees or vines interfering with wires 5. Wires too close to doors or windows 6. Wires not well secured to the house 7. Poor connection between the service drop and service entrance 8. Inadequate clearance from roofs 9. Service lateral problems

What size copper wires are adequately protected by: a. 15 amp breaker b. 20 amp breaker c. 30 amp breaker d. 40 amp breaker

14 gauge wire needs 15 amp fuses or breakers 12 gauge wire needs 20 amp fuses or breakers 10 gauge wire needs 30 amp fuses or breakers 8 gauge wire needs 40 amp fuses or breakers 6 gauge wire needs 60 amp fuses or breakers

The most common wire size for branch household circuits is ________ gauge?

14 wire is the most common in residential branch circuit.

Roughly 999 out of 1,000 houses have _____volts available (insert number)

240 volts

What is the largest single-phase service that you are likely to find in a house?

400 amp electrical service

What size copper wire would you expect to find on the service entrance for each of the following? A 60-amp service | A 100-amp service | A 200-amp service

60 amp service (10* copper, 8* aluminum) | 100 amp service (4* copper, 2* aluminum) | 200 (2/0* copper, 4/0* aluminum)

What is a split receptacle?

A split receptacle has the top part of the outlet on one circuit and the bottom part on a different circuit.

Abandoned wire should be _____.

Abandoned wire should be removed.

What is meant by open splice?

All connection or splices should be in junction boxes. A open splice is not made inside a junction box.

If you can't read he size of the fuses in the service box, you should remove them try to get a better look.

Do not touch anything in the service box.

What does the term "double tap" mean?

Double tapping (double lugging) is the term for attaching two wires o a single fuse or breaker. Most

List two functions of the drip loop.

Drip loop is designed to prevent the water getting into the conduit and to show that the service drop wires are not straining the splices.

The grounding electrode conductor may also be called.

Earth ground wire

From the point where the ground and the neutral wires connect, there are two paths to ground. What are they?

Equipment Grounding and Earth Grounding Systems

A fused 200 amp service has two 100 amp fuses in the service box.

False

All service entrance conductors must be attached above roof level.

False

All service entrance conductors must be in conduit?

False

Subpanels must be immediately adjacent to the main panel.

False

The drip loop should be as close to the roof as possible.

False

Wires run directly from the service box to the branch circuits. True or False

False

What would four wires mean?

Four wires coming into the house indicate a three phased system. This a commercial electrical system and beyond the scope of standard home inspection.

How should the feeder wires to a subpanel from the main panel ideally be protected?

Fuses should be provided at the main panel

Load calculation are part of a home inspection.

Home inspectors don't do detailed load calculations.

Give four examples of damaged wire?

Includes wire that has been cut or pinched, wire that has been chewed on by pests, burned wire, and wire with cracked (brittle) insulation.

What is the difference between insulation and sheathing?

Insulation refers to the material wrapped around the individual wires. The sheathing forms the cable, wrapping around the insulated black, white, and possibly red wires and the uninsulated ground wire.

What are the two functions of earth grounding systems?

Is a path for lighting or static electricity | Grounding systems can help dissipate electricity from lighting.

Wires should not run on wall surfaces without _____.

Mechanical Protection

What is the advantage of a 240-volt circuit?

More electricity can flow at lower amp ratings

What size wire is found on most general purpose outlets for lights and receptacles?

Most circuits for receptacles and lights use 14 gauge wire.

Should the neutral and the ground wires be bonded together at the subpanel?

No. Because electricity may flow through the ground wire under normal circumstances. The ground wire should be reserved for emergency situations.

Implications of an undersized service include which of the following?

Nuisance tripping of the main fuses or breakers

Explain why fused neutrals are a bad idea.

Only the fuse on the neutral side blows. The circuit may not work, but there may be voltage throughout the entire circuit.

What are the implications of oversized breakers?

Oversized breakers will allow wires to overheat without tripping.

Distribution panels are also called (list six other names if you can)

Panelboards, auxiliary panels, subpanels, fuse boxes, fuse panels, or breaker panels

List 17 common conditions you might find in a service box.

Poor access or location, Loose, Rust or water in box, Unprotected openings (cover loose or missing, knockouts missing), Inappropriate support material, Damaged parts, Overheating, Incorrect fuse or breaker size; box rating too small, Service entrance wires exposed in the house, Poor connections, Improper taps, Neutral wire by passes service box, Fused neutral wire, Fuses upstream of disconnect switch, Obsolete box, Exterior box not weathertight, Box not rated for aluminum

A grommet is _________.

Protects the wire where it passes through the studs.

Does knob and tube wiring have a ground wire associated with it?

Remember that there will be no original equipment ground wires anywhere in the distribution system with knob and tube wiring.

The grounding system are connected to the house neutral at the_____.

Serice Box

The service entrance conductors run from the _______to the ________

Service box to the Service drop

List three methods for securing wire ends?

Terminal screws, push-in connectors, or solderless connectors

Describe how knob and tube wiring is visibly different from modern cable.

The black and white wires are separated, so the circuit wires usually run in pairs. There are ceramic tubes protecting the wires where they pass through joists or studs. There are ceramic knobs where the wires change direction.

What is implication of a panel that is too small for the service?

The panel may overheat.

Which of the following is a reliable way to identify the service size?

The service entrance conductor size

List clearances above ground, swimming pools, and roofs.

The wires need only be 10 feet above a walking surface, 12 feet above a driveway, and 18 feet above a roadway. Wires near swimming pools must be 22 1/2 feet away in any direction from the water.

Roughly 999 out of 1,000 houses have___service entrance wires (insert a number)

Three

How many wires would you typically find in a 240-volt service drop?

Three wires

Aluminum is an acceptable service entrance conductor material. True or False?

True

The red and black wires of multi-wire circuits should be on separate bus bars?

True

What would two wires usually mean?

Two wires spliced into the service entrance cable indicate a 120 volt service. This is a rare and not adequate for modern lifestyles.

Are the lateral overhead or underground?

Underground wires

Do we normally shut off the power when looking at the electrical system in the house? Why or why not?

We do not shut off the power. This would be a significant inconvenience to the occupant.

What are the issues on running wire through steel studs?

Wires may be damaged by sharp edges of steel studs. Wires passing through holes should be protected with grommets, for examples. Wires running parallel to studs should stand off the studs.