Free E2 Services, Feeders, Branch Circuits Questions and Answers 1

Question 1

In a commercial office building, a multiwire branch circuit supplies power to several cubicles. According to NEC 210.4(B), what is required at the point where this branch circuit originates?

Accepted Answer

A means that will simultaneously disconnect all ungrounded conductors.

Answer

NEC 210.4(B) requires that each multiwire branch circuit be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates. This is a critical safety measure to prevent personnel from working on a circuit they believe is de-energized when one of the ungrounded conductors is still live. This is typically achieved with a multi-pole circuit breaker or single-pole breakers with an identified handle tie.

Question 2

An inspector is reviewing plans for a commercial kitchen. Which of the following 125-volt, single-phase receptacles requires GFCI protection according to NEC 210.8(B)?

Accepted Answer

A receptacle installed within 6 feet of the top inside edge of a food preparation sink.

Answer

NEC 210.8(B)(2) requires GFCI protection for personnel for 125-volt through 250-volt receptacles supplied by single-phase branch circuits rated 150 volts or less to ground installed in commercial kitchens. The 2023 NEC clarifies this applies to areas with sinks and permanent provisions for food preparation or cooking. Receptacles within 6 feet of a sink fall under this requirement.

Question 3

A feeder is installed in a commercial building to supply a subpanel. The feeder conductors are protected by a 200A overcurrent device. According to the '25-foot tap rule' in NEC 240.21(B)(2), what is the minimum ampacity required for tap conductors that are 20 feet long?

Accepted Answer

67A

Answer

According to NEC 240.21(B)(2), for feeder taps not over 25 feet long, the tap conductors must have an ampacity of not less than one-third (1/3) the rating of the overcurrent device protecting the feeder conductors. In this scenario, 200A / 3 = 66.7A. Therefore, the tap conductors must have an ampacity of at least 67A.

Question 4

A commercial service is calculated to supply a continuous load of 160A and a noncontinuous load of 80A. Per NEC 230.42(A), what is the minimum required ampacity for the service-entrance conductors?

Accepted Answer

280A

Answer

NEC 230.42(A)(1) requires service-entrance conductors to have an ampacity of not less than 125 percent of the continuous loads plus 100 percent of the noncontinuous loads. The calculation is (160A x 1.25) + 80A = 200A + 80A = 280A.

Question 5

Which of the following is a requirement for identifying the grounded conductor of a feeder, according to NEC 215.12(A)?

Accepted Answer

It must be identified in accordance with the methods specified in NEC 200.6.

Answer

NEC 215.12(A) specifically states that the grounded conductor of a feeder must be identified in accordance with NEC 200.6. NEC 200.6 provides the acceptable methods for identifying grounded conductors, which typically involve a continuous white or gray outer finish or markings at the terminations.

(E2) E2 Commercial Electrical Inspector Practice Test

(E2) E2 Commercial Electrical Inspector Practice Test

Free E2 Services, Feeders, Branch Circuits Questions and Answers 1