Electrical

What are three main differences between aluminum and copper as conductors?

1. Aluminum has a higher co-efficient of thermal expansion than copper. This leads to the wire trying to move out from under terminal screws This is called "creep" 2. Aluminum is softer than copper. The wires would get nicked inadvertently. 3. The oxide that forms on the wire is a very poor electrical conductor. The oxide that forms on aluminum corrodes.

Name six common appliances with three-pronged plugs.

1. Automatic Clothes Washer 2. Portable Dishwasher 3. Microwave Oven 4 Some Refrigerators 5. Vacuum Cleaners 6. Kettles 7. Many Power Tools 8. Computers 9. Water Bed Heaters

How many wires run to a 240 volt stove?

3 wires.

In a modern house, how far apart should electrical outlets be located? Every ___ feet.

6 feet horizontally along the wall.

What size copper service wire would be needed to provide a house with: 60 amp service? 100 amp Service? 200 amp service?

60 amp - 6AWG 100 amp - 4AWG 200 amp - 2/0AWG

What is the frequency of modern household electricity?

60 cycles per second. (Hrz)

Why is reversed polarity this considered unsafe?

A floor lamp is a good example of an appliance that now has a polarized plug. There are two electrical components when changing a light bulb that may be live. The threaded collar and the brass button at the bottom of the bulb. A person is more likely to touch the threaded collar. So it is considered safer to make the collar the white(neutral) connection.

Briefly describe the purpose of grounding.

A ground wire is a wire that connects all electrical systems to the ground.

Would a larger or smaller aluminum wire be needed to carry the same amount of current as a copper wire?

A larger aluminum wire would be needed.

How is AFCI protection provided?

AFCI protection may be provided by a breaker in the electrical panel, or through special AFCI receptacles.

What type of current is used for houses, AC or DC?

Alternating Current

What do AC and DC stand for?

Alternating Current : Direct Current

What type of wire should be used outdoors?

Exterior wiring should be a type suitable for outdoor use (typically NMW cable)

True or false. A house has a 100 amp distribution panel and a 60 amp auxiliary panel. The power into the house must be 160 amps.

False.

True or false. Aluminum wiring is better conductor than copper.

False.

True or false. Aluminum wiring is unsafe and any house containing it should be re-wired.

False.

True or false. An electrical system is properly grounded if it is clamped to any plumbing pipe in the house.

False.

True or false. Breakers are safer than fuses. Any house with fuses should be upgraded to breakers.

False.

True or false. In most cases, three distribution wires connected to one fuse or breaker is acceptable.

False.

True or false. Reversed polarity is considered unsafe because of the risk of fire.

False.

True or false. The main disconnect has two 100 amp fuses. This indicates the house has a 200 amp service.

False.

True or false. Older homes with 60 amp services are unsafe. They should all be replaced with 100 amp services.

False. A undersized service is not a safety concern but it can be an inconvenience.

True or false. An outlet with a three-prong receptacle is considered to be grounded.

False. It is sometimes impossible to determine visually whether an outlet is grounded. In houses built in 1960's or later all outlets "should" be grounded.

True or false. The distribution panel rating should be the same as or smaller than the main disconnect fuses or circuit breakers.

False. The panel should be same or larger.

True or false. A main disconnect box is rated for 60 amps. It is safe if 100 amp fuses are inserted.

False. This is a safety hazard. It can potentially lead to overheating.

True or false. It is acceptable to add a second wire to the terminal screw.

False. This is not permitted, unless a special connector designed to hold two wires is provided. Securing three wires under on e terminal screw is never acceptable.

What issues can arise from using a pig tail?

First - every connection added to an electrical system is one more potential problem area. Second - adding one more connection can cause overcrowding in a junction box.

What voltage is supplied to most houses today?

Most houses today are provided with a nominal 240 volts.

What precaution should be taken when locating and outlet in a bathroom?

Outlets should be as a far away from the bathtub or shower as is practical. At least 3 feet.

List five kinds of sheathing on household wires?

Paper Cloth Rubber Plastic Metal

Define power.

Power is calculated by multiplying the voltage times the current. It is measured in watts. (P=VI)

What is the most common electrical flaw found in homes?

The most common electrical flaw found residentially is fuses which are wrong size for a circuit wire.

List six household circuits that require linking of fuses or breakers.

The overcurrent protection devices for any circuit with more than one powered connection must power to both legs simultaneously. This includes 240 volt appliances 1) Electric Stove 2)Clothes dryer 3)Water Heater 4)large Air Conditioner 5)Some Electric Heaters 6)Split Kitchen Receptacles

If the black, or hot wire, carries 10 amps, how much current does the white, or neutral wire usually carry?

The same. 10 amps.

What factor determines how much electricity is available to the house?

The size of the service entrance determines how much electricity is available to the house.

Why is the nicked wire potentially unsafe?

The wire is effectively smaller where it is nicked. The smaller the wire diameter, the more difficult it is for electricity to move through.

How many wires are there from the street into a house ina 240-volt system?

There are 3 wires.

In a lighting and receptacle branch circuit, how many wires usually make up one cable?

There are 3 wires. Hotwire, Neutral and Ground.

What is a GFCI?

These special electrical devices shut the power off to a circuit when as little as .005 amps is leaking.

What are AFCI's designed to protect?

They are designed to protect against fires while GFCI's are designed to protect against electrical shock.

What is the purpose of fuses and/or circuit breakers?

They are overcurrent protection devices. They shut off the power when more current, than is supposed to is flowing through the circuit.

How were connections made with knob and tube wiring?

They where made by twisting the wiring together, soldering the wires and wrapping the connection in rubber.

How can a system ground be easily improved when it is clamped to the plumbing pipe downstream of the water meter?

This can be corrected by relocating the ground wire upstream of the water meter, or providing a jumper wire around the meter.

What is a kilowatt hour?

This is the measure of electricity consumption. IF 1000 watts are used continuously for 1 hour, than 1 kilowatt- hour has been consumed.

True or false. Distribution wires on the surface of the walls or interior finishes are safe if well secured.

True.

True or false. The size of the fuses or breakers at the main disconnect will almost always tell you how much electricity is available to the house.

True.

True or false. The two main fuses should be the same size.

True.

True or false. Wire should be secured in place where they pass through the walls of the box.

True.

True or false. The ground wire must must be clamped to the supply water pipe upstream of the water meter.

True. If connected downstream a jumper wire should be provided.

True or false. Linking is used to ensure two fuses or breakers are disconnected at the same time.

True. The overcurrent protection devices for any circuit with more than one powered connection must power to both legs simultaneously. This includes 240 volt appliances.

True or false. A main disconnect is rated for 200 amps. It is safe if 100 amp fuses are inserted.

True. This can be an inconvenience. The fuses can pop if the draw is to strong.

What is a type "D" fuse?

Type "D" fuses are a tied fuse. They will allow more than the rated current to flow for a short period of time.

What is a type "P" fuse?

Type "P" fuses have a low melting temperature, which makes this fuse very sensitive to heat build up around the fuse. A loose wire with a current of less than 1-amp can lead to overheating and eventually fire.

How deep should a set of underground wires be?

Underground wires should be at least 24 inches deep below landscapes and 36 inches deep below driveways or parking areas.

Each piece of cable is made up of two conductors and one ground wire. The copper conductors are wrapped with insulation, usually _________ or _________.

rubber or plastic.

The largest gauge of solid wire is?

10 gauges.

If a service box has two 100 amp breakers as its mains what is the service to the house?

100 amps. The two can not be added together.

What size aluminum wire would be used in place of 14 gauge copper? 10 gauge copper?

12 gauge Aluminum for 14 gauge Copper 8 gauge Aluminum for 10 gauge Copper

What voltage is a typical household circuit?

120 volts

What is the maximum amperage or current for the following household wiring gages? AWG #14. #10. #6. #3. #3/0.

14AWG=15Amps 10AWG=30Amps 6AWG=75Amps 3AWG=110Amps 3/0AWG=225Amps

How high should a set of overhead wires be? At least _________.

15 feet above ground and 3 feet away from windows. Where a conduit protrudes through a roof it should be flashed to prevent leaks.

Since ______ grounding has been required on all branch circuits.

1960

Aluminum wiring was commonly used in residential construction from _________ to _________.

1960's to about 1978.

In most hoses the electrical systems are grounded to the water supply piping. In the U.S. since ______, a driven _________ _________ is required in addition.

1987. Ground Rod

How many fuses or breakers are there on 240 volt appliances?

2 fuses/breakers. They should have a rod that allows them to be shut off at the same time.

Knob and Tube style wiring was used until _________.

Approximately 1950

What is an AFCI?

Arc Fault Circuit interrupter. AFCI's help to protect against fires by detecting arc faults.

How many outlets can be connected to a branch circuit?

At a maximum, 12 outlets may be connected.

Identify the function of the wire by its insulation color. Black. Red. White. Bare.

Black - live/hotwire Red - live/hotwire White - Neutral Bare - Ground/Escape Path

What color are the conductors?

Black, Red and White.

Where are GFCI's found in new houses?

Builders often use one GFI in a main floor washroom to protect all the bathroom outlets in the house.

Define Current.

Current is the flow of electricity that results when a voltage is applied across a given resistance. It is measured in amps.

List five 240 volt appliances used in houses.

Electric Ranges Stoves Clothes Dryers Air Conditioners Water Heaters

How are aluminum-compatible 120 volt receptacles designated?

Electrical outlets are designated CO/ALR.

How are electrical systems grounded on rural properties where the supply plumbing pipe into the house is plastic?

IN the U.S a single ground rod is used.

What is the danger of a damaged or poorly connected wire?

If a wire is nicked or poorly connected it is essentially a smaller size. A standard current on the wire can than lead to overheating in this case.

When would a system ground be ineffective?

If the ground wire is missing. If the connection is poor. If there is a splice in the ground wire. If the pipes the ground wire is secured to are no longer in service.

A 60 amp service ample electricity to a home. What situations might arise that make upgrading a 60 amp service to a 100 amp service necessary?

If the rating of the panel is smaller than the upgraded incoming service.

When do the overhead wires leading to the house need to be replaced?

If the wires appear damaged or frayed notify your utility company.

How is the electrical system grounded in most homes?

In most houses it is grounded to the water supply system. In the U.S since 1987 a driven ground rod is required in addition.

Name another importance difference between knob and tube wiring and modern cable.

Is the presence of two fuses on a single circuit. Both the black and white have fuses on some older panels. None of the fixtures on the circuit will work but there is still power to the circuit. It is not safe to work on this way.

What is a "pig tail"?

It is a short copper wire used to jump aluminum wires to the outlet.

Define Voltage.

It is the potential of energy of the electrical system. Most houses are equipped 120/240 volts. (V=IR)

What does it usually mean if half of the house power is lost?

It means the a main fuse or breaker has blown.

In what decade was grounding introduced on branch distribution circuits in homes?

It was introduced to residential electric systems in the late 1950's

What is the most common reason for replacement of knob and tube wiring?

Renovations is the most common reason knob and tube wiring is removed.

Define resistance.

Resistance is the measure of electricity through any given material. It is measured in Ohms. When there is no resistance the electricity flow is very large!

What type of sheathing was used on knob and tube wiring?

Rubber and cloth insulation around the wire.

How are aluminum-compatible components, such as wire connectors, boxes and circuit breakers designated?

Service Panels and their components are designated Cu-AL.

Where would a dedicated circuit be useful?

Some appliances need a dedicated circuit. This can include furnace, boiler, dishwasher, food waste disposal, compactor, central vacuum system, refrigerator, freezer, washing machine, whirlpool, and electric heaters.

What do the different color wires on a service entrance indicate?

The Black and Red wires are live. The White wire is neutral. The potential between either black and white or red and white is 120 volts and between red and black is 240 volts.

Name two things that determine the amount of electricity a wire can carry?

The amount a wire can carry (in amps) is determined largely by its diameter and wire material.

What are the colors in a wire and what do they mean?

The black wire is live. The white wire is neutral. The naked wire is the ground.

What is the purpose of the main service conduit outside a house?

The conduit or cable from the overhead service should be well secured the house and should not allow water to enter.

Why are main switches often sealed by the utility company?

The first reason Safety. There is live electrical power inside the box, even if the main switch or breaker is shut off. The second reason is that the service box is located upstream of the meter. The seal discourages people from trying to steal electricity.

What is the main difference between knob and tube wiring and modern cable?

The main difference is that the black and white wires run separately from each other.

When does a circuit become overloaded?

When a branch circuit draws more than 15 amps it becomes overloaded.

What is reversed polarity?

When the black wire is connected to the silver screw on the outlet, and the white wire is connected to the brass screw, this is referred to as reverse polarity.

List five possible causes of an inoperative light?

a) A burned bulb b) A faulty light fixture c) A poor connection in the box d) A flaw in the wiring leading to the box e) A problem with the switch controlling the light f) A problem with the wire between the panel and the switch g) A blown fuse or tripped breaker h) A poor connection within the panel

List five possible causes of an inoperative outlet.

a) The outlet itself is defective b) The wires inside the box at the outlet are not properly connected. (Intermittent problems usually mean a loose connection) c) There is a problem in the wire between the panel and the outlet (perhaps at another box upstream d) There is a blown fuse or tripped breaker in the panel e) There is a poor connection or damaged wire in the panel f) the power has been turned off