CME System Design and Installation Questions and Answers

Question 1

A 3-phase, 480V motor has a full-load current (FLC) of 65A per Table 430.250.
The branch circuit will be protected by an inverse-time circuit breaker.
According to NEC 430.52(C)(1), what is the MAXIMUM standard size circuit breaker permitted for short-circuit and ground-fault protection?

Accepted Answer

175A

Answer

150A

Answer

200A

Answer

125A

Question 2

An electrical installation in a commercial building is modified by the utility, resulting in a higher available fault current (AFC) at the service equipment. Per NEC 110.24(B), what is the primary action required by the master electrician?

Accepted Answer

Recalculate the AFC and adjust the field-installed label on the service equipment.

Answer

Notify the building owner in writing of the change.

Answer

Replace all downstream circuit breakers with higher interrupting rated devices.

Answer

Request a variance from the AHJ to accept the existing equipment.

Question 3

Which of the following wiring methods is permitted to be installed exposed in a space used for environmental air handling above a lay-in ceiling (plenum), without being installed in a raceway?

Accepted Answer

Type AC (Armored Cable)

Answer

Non-metallic sheathed cable (Type NM-B)

Answer

Type MC cable with an overall nonmetallic covering

Answer

Service-entrance cable (Type SE)

Question 4

A 200A, 240V single-phase feeder supplies a panelboard located 250 feet from the source. To adhere to the NEC's recommendation to limit voltage drop to 3% on the feeder, what is the minimum size copper conductor required? (Use K=12.9 for copper)

Accepted Answer

250 kcmil

Answer

2/0 AWG

Answer

3/0 AWG

Answer

4/0 AWG

Question 5

For a system to be considered selectively coordinated, which of the following must occur during a fault condition?

Accepted Answer

The overcurrent protective device immediately upstream of the fault must open, while all further upstream devices remain closed.

Answer

The overcurrent protective device nearest to the source must open first.

Answer

All overcurrent protective devices in the fault path must open simultaneously.

Answer

The main service disconnect and the branch circuit breaker must both trip.

Question 6

An electrician is installing two parallel sets of 4/0 AWG copper conductors in separate non-metallic conduits. Which of the following is NOT a requirement for this installation per NEC 310.10(G)?

Accepted Answer

The conduits must be grouped together to minimize inductive heating.

Answer

Both sets of conductors must be the same length.

Answer

Each conductor within a phase must have the same insulation type.

Answer

The equipment grounding conductor in each conduit must be full-size.

A 3-phase, 480V motor has a full-load current (FLC) of 65A per Table 430.250.The branch circuit will be protected by an inverse-time circuit breaker.According to NEC 430.52(C)(1), what is the MAXIMUM standard size circuit breaker permitted for short-circuit and ground-fault protection?

A 3-phase, 480V motor has a full-load current (FLC) of 65A per Table 430.250.
The branch circuit will be protected by an inverse-time circuit breaker.
According to NEC 430.52(C)(1), what is the MAXIMUM standard size circuit breaker permitted for short-circuit and ground-fault protection?