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A.R.E. - Building Systems > BS: Lesson 6.2 - Electrical Systems > Flashcards

BS: Lesson 6.2 - Electrical Systems Flashcards

0
Q

In residences, refrigerators, A/C, electric ranges, and other semi-permanent appliances use what type and size of voltage?

A

line-to-line voltage of 240

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1
Q

Residences are limited to make size and type of voltage?

A

120V / 240V, single phase

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2
Q

In residential, receptacles and lights use what type and size of voltage?

A

line-to-neutral voltage of 120v

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3
Q

Small commercial buildings receive what size electrical service?

A

120/240 single-phase or 120/208 three-phase

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4
Q

Larger commercial buildings recieve what size electrical service?

A

277/480v three-phase or 2,400/4,160v three-phase

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5
Q

In the electrical service 120/208 and 277/480, which is the primary and secondary winding?

A

120 and 277 are the primary windings

208 and 480 are the secondary windings

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6
Q

Note:
Electric heaters are 100% efficient. Every bit of electrical energy is converted to heat. However, using electricity to heat a space is very wasteful. BUT, using electric heat as a radiant heat source is efficient because it heats only people and objects, not the air - good for spot heating.

A

n/a

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7
Q

A single electrical switch is called a ____?

A

two-way switch

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8
Q

List the three types of electric motors.

A

DC motor

AC motor - single-phase synchronous and 3-phase induction

universal motor

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9
Q

Where would you use a three-phase induction AC motor?

A

Extremely reliable motor providing a constant rpm, used in factories and industrial drives.

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10
Q

What is an universal motor?

A

A series wound motor that can run on either AC or DC current. It varies in speed based on the load. Found in hand mixers, drills, etc. Are the basis of railway motors.

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11
Q

Capacitors are used to _______ the power factor in a circuit.

A

improve

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12
Q

What are capacitors?

A

A passive two-terminal electrical component used to store energy. In circuits, they block DC current and allow AC current to pass.

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13
Q

In residential construction, electrical outlets should be spaced every _______ .

A

12 feet

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14
Q

In a electrical panelboard, circuit breakers are generally placed in two columns and numbered how?

A

From left to right, along each row from top to bottom

i.e.:
1 2
3 4
5 6

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15
Q

What is the smallest gauge used for building wire?

A

14

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16
Q

Which is larger?

8 gauge copper wire
250 MCM gauge copper wire
12 gauge copper wire
000 gauge aluminum wire

A

250 MCM

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17
Q

The rating of a motor should not be greater than _____ of the capacity of the circuit that feeds it.

A

80%

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18
Q

Any circuit expected to operate continuously or that carries a motor, the circuits rated load should be multiplied by _____ to determine the wire size.

A

1.25

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19
Q

Conduits are also known as ______.

A

a race way

20
Q

What electrical conduit can be buried in concrete?

A

PVC

21
Q

In applications where acoustic and vibration isolation is required, what type of conduit is used?

A

flex (aka Greenfield) - flexible metal conduit

22
Q

What conduit can be used in wet locations?

A

flex, with a plastic jacket

IMC (interlocked metal-clad)

23
Q

Which type of conduit is used in exterior applications?

A

galvanized rigid conduit

intermediate metallic conduit (IMC)

interlocked metal clad cable (MC)

PVC

24
Q

Cable designated as NM and NMC is referred to as ______ .

A

romex

25
Q

Which of these electrical wiring conduits can you NOT add wires to?

rigid
flex
armored cable
all of the above

A

armored cable

26
Q

Which electrical conduit is frequently used in residential and re-wiring applications?

A

interlocked armored cable (AC) (aka BX)

27
Q

A voltage drop due to resistances of the wire may be noticeable in a large or small circuit?

A

large

28
Q

What is the allowed voltage drop in a lighting circuit?

A

3% or less

29
Q

What is the allowed voltage drop in a circuit supporting a motor?

A

5% or less

30
Q

The architect can use watts/s.f. to establish what?

A

Estimate the overall electrical load and minimum lighting requirements

31
Q

Which has the greatest and least amount of electrical load?

lighting
outlest
HVAC
misc.

A

greatest = lighting at 2 - 5 watts/sf

least = misc. items at 0.2 - 0.7 watts/sf

32
Q

Define a short circuit.

A

A short circuit occurs when two adjacent conductors lose so much insulation that a current flows directly between them - anytime a current is flowing where it shouldn’t.

33
Q

What are the two electrical devices use to help protect against short circuits?

A

fuse

circuit breakers (including GFIs; breakers with thermal and magnetic trips)

34
Q

Which of these can be used as a “back-up” switch to shut-off an area or circuit?

circuit breaker
GFI
fuse
panelboard
light switch
A

circuit breaker

35
Q

GFIs are required in circuits with _______ .

A

15 or 20 amps that serves a bathroom, garage or temporary circuit for a construction sites. And all large high voltage circuits (i.e. 480/277v, 1,000 amps)

36
Q

In a wiring assembly, how is the ground wire identified?

A

either left bare or in green insulation

37
Q

What does a service drop refer to?

A

All the electrical services arriving on the site.

38
Q

What does a service drop consist of?

A 
the wires
main line
transformer
meter
disconnect switch
39
Q

The distance from the transformer to the meter should not exceed _____ ft.

A

150

40
Q

What is the minimum electrical service for a residence?

A

100 amp

41
Q

How is the consumption of electricity in residential and commercial applications is measured?

A

Residential - measured by the total consumption of kilowatt hours at 18 cents per kwh

Commercial - peak demand + a demand surcharge

42
Q

How is the demand surcharge calculated?

A

maximum demand x tarrif

43
Q

List three advantages and disadvantages of using fuses.

A

Advantages:
simple and fool proof
cheap
no maintenance

Disadvantages:
non-adjustable
non-renewable
not trip-free

44
Q

List three advantages and disadvantages of circuit breakers.

A

Advantages:
usable as switches
resettable
trip-free

Disadvantages:
maintenance required
high initial cost
low to medium interruption capacity

45
Q

The general equation for power in a DC circuit is:

A

P = V X I

power = volts x current

46
Q

The general power equation for single-phase circuit is:

A

P = V x I x PF

power = volts x current x power factor

47
Q

The general power equation for a three-phase circuit is:

A

P = V x I x PF x /3 [sq. root of 3]

power = volts x current x power factor x square root of 3 [1.78]

A.R.E. - Building Systems (8 decks)

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