E2 Systems and Equipment 2

Question 1

According to the NEC, what is the minimum clearance required above a switchboard in a commercial installation?

Accepted Answer

6 feet

Answer

NEC 110.26(A)(1) requires a minimum of 6 feet of headroom above electrical equipment such as switchboards.

Question 2

A commercial building's emergency lighting system is required to provide illumination for at least how long upon loss of normal power?

Accepted Answer

90 minutes

Answer

NEC 700.12 requires emergency lighting systems to provide at least 90 minutes of operation upon normal power failure.

Question 3

When inspecting a variable frequency drive (VFD) installation, which conductor issue is most critical to verify?

Accepted Answer

Conductor ampacity derating for harmonic heating

Answer

VFDs produce harmonics that cause additional heating in conductors, requiring ampacity derating per NEC 310.15(A)(2).

Question 4

Under the NEC, a motor controller must be capable of interrupting the stalled-rotor current of the motor it controls. This rating is known as the:

Accepted Answer

Locked rotor current (LRC)

Answer

Motor controllers must be rated for locked rotor current (LRC), which is the maximum current drawn when the motor shaft is stalled.

Question 5

In a commercial kitchen, a dishwasher is hardwired to a 20-ampere, 120-volt circuit. The NEC requires this circuit to be protected by a:

Accepted Answer

Standard GFCI breaker

Answer

NEC 210.8(B) requires GFCI protection for commercial kitchen equipment in areas where water is present.

(E2) E2 Commercial Electrical Inspector Practice Test