Free E2 Services, Feeders, Branch Circuits Questions and Answers 1 — Questions and Answers
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?
- A means to individually disconnect each ungrounded conductor.
- A single-pole circuit breaker for each ungrounded conductor.
- A means that will simultaneously disconnect all ungrounded conductors. (Correct answer)
- An overcurrent device rated for the sum of the connected loads.
Correct answer: A means that will simultaneously disconnect all ungrounded conductors.
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)?
- A receptacle for a clock located 8 feet above the floor.
- A receptacle installed within 6 feet of the top inside edge of a food preparation sink. (Correct answer)
- A receptacle inside a walk-in freezer dedicated to the freezer unit.
- A receptacle located in an adjacent dry storage pantry.
Correct answer: A receptacle installed within 6 feet of the top inside edge of a food preparation sink.
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?
- 50A
- 100A
- 200A
- 67A (Correct answer)
Correct answer: 67A
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?
- 240A
- 200A
- 280A (Correct answer)
- 300A
Correct answer: 280A
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)?
- It must be identified with green tape at all termination points.
- It must be larger in size than the ungrounded conductors.
- It must be identified in accordance with the methods specified in NEC 200.6. (Correct answer)
- It must be bonded to the equipment grounding conductor within the panelboard it supplies.
Correct answer: It must be identified in accordance with the methods specified in NEC 200.6.
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.
Question 6: During a commercial building inspection, you observe a feeder supplying a separate building. Which NEC article must be consulted to ensure the grounding and bonding requirements at the separate building are met?
- Article 210 - Branch Circuits
- Article 230 - Services
- Article 240 - Overcurrent Protection
- Article 250 - Grounding and Bonding (Correct answer)
Correct answer: Article 250 - Grounding and Bonding
NEC 215.6 requires that where a feeder supplies a separate building or structure, the grounding and bonding requirements of Article 250, specifically 250.32, shall apply. This section details how to establish a grounding electrode system and handle the equipment grounding conductors and system bonding at the separate structure.
Free E2 Services, Feeders, Branch Circuits Questions and Answers 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?