Deck 8: Feeder Installation and Load Calculation

Question 1

What are the requirements for installing parallel conductors, as specified in NEC 310.10( G )?

Answer 1

​
The parallel conductors are required to be 1/0 AWG or larger and have the same insulation type. They must also be of the same length and of the same material (copper-copper or aluminum-aluminum). They must be the same size in terms of circular mil area, and be terminated in the same manner. In addition, the raceway or cables are required to have the same electrical characteristics.

Question 2

In the United States, ____ Hz is standard or the fundamental frequency.

A)30
B)60
C)90
D)120

Answer 2

B

Question 3

Often the load is such that parallel conductors should be considered. This usually occurs with loads over ____ amperes.

A)100
B)400
C)900
D)1600

Answer 3

B

Question 4

What wire and cable options do you have for combating excessive neutral current?

Question 5

Feeders are the part of the electrical system that connects the branch-circuit ____ to the electrical service equipment.

A)motors
B)busbars
C)raceways
D)panelboards

Question 6

To get accurate current readings where harmonics are involved, ammeters referred to as "____" must be used.

A)neutral
B)clamp-on
C)average-reading
D)true rms

Question 7

If the ampacity of a feeder does not match a standard OCPD rating, then ____ be used.

A)the next higher standard rating may
B)the next lower standard rating may
C)a custom rating may
D)a custom rating must

Question 8

If a lighting load is considered to be continuous, as is the case in commercial buildings, a load factor of ____ percent must be applied.

A)100
B)120
C)125
D)150

Question 9

If the selected OCPD has a rating greater than 100-amperes, the conductors to be installed shall be selected from either the 75 degrees Celsius or ____ degrees Celsius column of NEC Table 310.16 .

A)60
B)90
C)100
D)110

Question 10

For installations where the nonlinear load is huge, most consulting engineers will specify ____-rated transformers.

A)D
B)K
C)T
D)Y

Question 11

____ are multiples of a fundamental frequency.

A)Overcurrents
B)Linear loads
C)Standing waves
D)Harmonics

Question 12

Currents of the 3rd harmonic and odd multiples of the 3rd harmonic (9th, 15th, 21st, etc.)add together in the common neutral conductor of a 3-phase system, instead of canceling each other. These odd multiples are referred to as ____.

A)triplens
B)doublens
C)triple harmonies
D)common harmonics

Question 13

When sizing feeder conductors, ____ noncoincident loads (loads unlikely to be operated simultaneously such as the air-conditioning and the heating)need be included.

A)all of the
B)the average of the
C)only the larger of any
D)only the smaller of any

Question 14

When a smaller conductor is tapped from a larger conductor, the overcurrent protection at the beginning of the tap is ____ the ampacity of the smaller conductor.

A)less than
B)greater than
C)equal to
D)unrelated to

Question 15

​What guidelines are given to deal with local energy code regulations?

Question 16

To determine a reasonable minimum size for a neutral conductor, two types of loads must be considered-____.

A)fuses and circuit breakers
B)series and parallel
C)linear and nonlinear
D)motors and hermetic units

Question 17

NEC 310.10 ( G )sets forth the requirements for installing ____ conductors. These requirements are intended to ensure the conductors will share the current equally to prevent overloading individual conductors.

A)phase
B)neutral
C)parallel
D)serial

Question 18

On a 3-phase, 4-wire, wye system, ____ reduction is allowed for nonlinear loads.

A)no
B)10 percent
C)50 percent
D)75 percent

Question 19

What three circuit parameters must be known before feeder component selection can begin?

Question 20

What are the three conditions of failure that may occur with a 3-phase, 4-wire wye system?

Question 21

A common example of a tap is for fixture whips that connect a ____ to a branch circuit.

A)luminaire
B)transformer
C)circuit breaker
D)smoke detector

Question 22

Branch-circuit conductors must have an ampacity not less than the ____ served.

A)maximum load
B)minimum load
C)average load
D)average 3-phase load