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May NEC Questions

NEC Questions and Answers (Based on the 2005 NEC)

By Mike Holt for EC&M Magazine

Q1. Does the Code allow armored cable to terminate into a plastic box?

A1. No. Nonmetallic boxes are not permitted to be used with a metallic wiring method because there is no way to maintain the electrical continuity of the effective ground-fault current path [250.2 and 314.3].

However, Exception No.1 of 314.3 does permit metal raceways and metal cables with nonmetallic boxes, but only if an internal bonding means is provided in the box between all metal entries. In addition, Exception No. 2 recognizes the use of nonmetallic boxes with metallic wiring methods; if integral bonding means with a provision for attaching an equipment bonding jumper inside the box between all threaded entries are provided.

Q2. Can I install control wiring in the same raceway with electrical power conductors for an electric gate?

A. Maybe. According to 725.25(B)(1), Class 1 circuits can be in the same cable, enclosure, or raceway with power-supply circuits, if the equipment powered is functionally associated with the Class 1 circuit. But 725.55(A) states that Class 2 and Class 3 circuit conductors must not be placed in any enclosure, raceway, or cable with conductors of electric light and power.

How do you know if you have a Class 1 or Class 2 circuit? Check with the manufacture and find out if the control circuit power supply is intended for Class 2 or Class 3 wiring.

However, 725.52(A) Exception 2 allows you to reclassify a Class 2 or Class 3 circuit into a Class 1 circuits if the Class 2 and Class 3 equipment markings required by 725.42 are eliminated and the entire circuit is installed in a Chapter 3 wiring method [725.55(D)(2)(b)].
Class 2 and Class 3 circuits reclassified and installed as Class 1 are no longer Class 2 or Class 3, regardless of the continued connection to a Class 2 or Class 3 power source.

Q2. Under what condition can a two-wire receptacle be replaced with a three-wire receptacle, when no ground is available in the box?

A. Where no equipment bonding means exists in the outlet box, nongrounding-type receptacles can be replaced with [406.3(D)(3)]:

  • Another nongrounding-type receptacle.
  • A GFCI grounding-type receptacle marked "No Equipment Ground."
  • A grounding-type receptacle, if GFCI protected and marked "GFCI Protected" and "No Equipment Ground."

Note: GFCI protection functions properly on a 2-wire circuit without an equipment grounding (bonding) conductor, because the equipment grounding (bonding) conductor serves no role in the operation of the GFCI-protection device.

CAUTION: The permission to replace nongrounding-type receptacles with GFCI-protected grounding-type receptacles doesn't apply to new receptacle outlets that extend from an existing ungrounded outlet box. Once you add a receptacle outlet (branch-circuit extension), the receptacle must be of the grounding (bonding) type and it must have its grounding terminal grounded (bonded) to an effective ground-fault current path in accordance with 250.130(C).

Q3. I am running a 4-wire lighting circuit with a shared neutral. Can I use three single-pole breakers without handle ties?

A3. Yes. Individual single-pole breakers can be installed on each ungrounded conductor of a multiwire branch circuit that supplies line-to-neutral loads for lighting or receptacle circuits [240.20(B)(1)].

However, multiwire branch circuits that supply switches, receptacles, or equipment on the same yoke must be provided with a means to disconnect simultaneously all ungrounded conductors that supply those devices or equipment at the point where the branch circuit originates [210.4(B) and 210.7(B)]. This can be accomplished by single-pole circuit breakers with handle ties identified for the purpose or a 2- or 3-pole breaker with common internal trip.

Q4. Can an AFCI protected circuit leave the bedroom of a dwelling unit and supply other receptacle or lighting outlets?

A4. Sure. There is no Code requirement limiting the use of AFCI protected circuits to bedroom outlets

Q5. Is a switch in a bedroom for an outside light required to be AFCI protected?

A5. No. The requirement of 210.12(B) is that all 15 or 20A, 120V branch circuits that supply outlets in dwelling unit bedrooms must be protected by a listed AFCI device. However, the circuit conductors for a switch controlling a lighting outlet, that is not located in the bedroom, is not required to be AFCI protected.

According to Article 100, an outlet is defined as a point in the wiring system where electric current is taken to supply a load. This would include receptacle outlets, lighting outlets, as well as outlets for paddle fans and smoke detectors, but not switches.

Q6. An electrician installed a two-wire 20A receptacle circuit (12 AWG) with six 15A, 125V duplex receptacles. He wired the receptacles as feed thru (daisy chain) using the 4 screws on the receptacles. The inspector would not accept the installation and said that he had to splice the wires and leave a pigtail to connect to only 2 screws of the receptacle. Is this a NEC requirement?

A6. No.

Q7. I'm wiring a showroom at a car dealership. We installed the receptacle outlets at 16" to center and the electrical inspector says it is a code violation because there is a door to the service garage.

He says a solid wall or partition (no doors) even though the door has a closure on it and is always closed. Also states this classification goes on thru multiple doors to any area, unless the air ventilation or air pressure exceptions apply. Is my installation in violation of the NEC?

A7. Yes. The area adjacent to a classified location up to 18 in. above the floor is classified as a Class I, Division 2 location, unless mechanically ventilated at a rate of four or more air changes per hour, or when walls or partitions effectively cut off the adjacent area [511.3(A)(3) and 511.3(B)(1)].

Q8. I am installing a12A, 240V "wet saw," and the manufacturer requires the motor to have GFCI protection. I don't believe this motor can be GFCI protected because it doesn't have a neutral. Do we need GFCI protection on this equipment?

A8. Yes. GFCI protection is required because equipment must be installed and used in accordance with any instructions included in the listing or labeling requirements. Oh yea, a neutral is not necessary for the proper operation of a two-pole GFCI circuit breaker.

Q9. My electrician stated that if he were to wire my aboveground storage pool pump motor for 240V operation, the receptacle outlet would need to be 10 feet away from the pool. I though 5 feet was the minimum. Who right?
A9. Your electrician buddy is almost right. According to 680.34, all receptacles must not be located less than 10 ft from the inside walls of a storable pool. So you see voltage is not an issue. In addition, GFCI protection is required for all electrical equipment, including power-supply cords, used with storable pools [680.32]. If I were you, I'd connect the pool pump motor to a 125V GFCI receptacle that's located 10 ft or more away from the pool.

Q10. Can Type MC armored cable of the interlocked type be use for the wiring of luminaires in the examining rooms of a doctors office?

A10. Nope. All branch circuits that serve patient care areas must be installed in a metal raceway or listed cable with a metallic armor or sheath that qualifies as an effective ground-fault current path in accordance with 250.118. Typically, the outer metal sheath of interlocked Type MC cable isn't listed as a suitable ground-fault current path [250.118(10]). Therefore, it is not permitted to supply branch circuits in patient care areas of health care facilities.

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02. NEC Exam Practice Questions Textbook
The NEC Exam Practice Questions Book contains 2,400 questions from the National Electrical Code. There are 12 review quizzes of 100 questions each that are in code order and take you step-by-step through each of the 9 chapters of the National Electrical Code. The 12 practice quizzes of 50 questions each follow the NEC Review quizzes, but are presented in random order and contain questions different than those in the review quizzes.

In addition, this book contains 12 challenge quizzes of 50 questions each that cover all 9 chapters of the National Electrical Code. The questions in the challenge quizzes do not follow the chapters of the Code book as the other quizzes do, they are also organized in a random manner, and you might find them harder to answer. Scores for the first few challenge quizzes might be somewhat lower than you would like to see. But, as you go through this book and take the review and practice quizzes, you’ll learn a great deal and gain a better understanding of the material. This improved knowledge and understanding will help you improve on the challenge quizzes as you go.

Product Code: 05PQ
ISBN: 1-932685-28-6

Available May, 2005

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