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NEC Questions and Answers - March Part 2 of 2

Topic - NEC Questions
- NEC Questions and Answers - March Part 2 of 2

March 29, 2007  

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NEC Questions and Answers - March Part 2 of 2


By Mike Holt for EC&M Magazine


Q1. Since the neutral is bonded to the case at the meter enclosure, do I still need to bond the neutral at the service disconnect?

A1. Yes, a main bonding jumper must be installed between the neutral terminal and the metal parts of the service disconnecting means enclosure in accordance with 250.24(C) [250.24(B)].


Q2. I have a small metal shed about 10 ft. from a swimming pool. Am I required to bond the metal shed to the pool’s equipotential grid?

A2. No. Only the fixed metal parts within 5 ft horizontally of the inside walls of the pool and 12 ft vertically above the maximum water level of a permanently installed pool, outdoor spa, or outdoor hot tub need to be bonded to the equipotential grid required in 680.26(C) [680.26(B)(5)].


Q3. Is AFCI protection of branch circuits required for hotel/motel rooms?

A3. No. AFCI protection is only required for 15 or 20A, 120V branch circuits that supply outlets in dwelling unit bedrooms [210.12(B)]. Article 100 defines a dwelling unit as a single unit that provides independent living facilities for persons, including permanent provisions for living, sleeping, cooking, and sanitation.


So if the hotel or motel room provides suites or extended stay accommodations which include permanent provisions for living, sleeping, cooking, and sanitation, then it’s a dwelling unit per Article 100.


Q4 Can I use 105°C conductors in a PVC raceway that is marked for use only with conductors having a maximum rating of 90°C?

A4. Yes. But the load on the conductors must be limited to the 90°C column of Table 310.16 so that the operating temperature of the conductors will not exceed the 90°C temperature rating of the conduit [352.12(E)].


Q5. I have a 50A receptacle for a range that says the terminations are rated for 75°C conductor sizing. I used 8 AWG Type NM cable, with 90°C conductors, and the inspector failed me. Where did I go wrong?

A5. The ampacity for conductors contained in Type NM cable is based on the 60°C rated column of Table 310.16, not the 90°C insulation rating of the conductors [334.80]. According to Table 310.16, 8 AWG is only rated 40A in the 60°C column, therefore you would be okay if the circuit was protected by a 40A device.


However, the largest range permitted on a 40A circuit would be 16 kW as per Table 220.55: Column C demand load for one 16 kW range using Note 1 would be 9.6 kW, and this works out to be 40A at 240V.


Q6. Can I install a single receptacle in a kitchen for a microwave appliance without GFCI protection?

A6. It depends on where the receptacle is located. In dwelling units, GFCI protection is required for 15 and 20A, 125V receptacles that are installed to serve countertop surfaces [210.8(A)(6)]. So if the receptacle for the microwave is installed so that it does not serve counter top surfaces, you are good to go, but be sure that the receptacle, circuit conductors, and protection device are sized in accordance with the manufacturer instructions (typically 20A). However 15 and 20A, 125V receptacles in commercial kitchens must be GFCI protected even if they are not serving the countertop surfaces [210.8(B)(2)].


Q7. Does the NEC require a specific coloring scheme for circuits?

A7. The neutral conductor must be identified with the color white or gray. For sizes larger than 6 AWG, marking tape or other identification is permitted, but for 6 AWG and smaller it must be the insulation finish color [200.6].


The equipment grounding conductor must be green or green with one or more yellow stripes if the conductor is insulated [250.119].


On a 4-wire, delta-connected, three-phase system, where the midpoint of one phase winding is grounded, the conductor with 208V voltage-to-ground must be durably and permanently marked by an outer finish orange in color, or other effective means. Such identification must be placed at each point on the system where a connection is made if the neutral conductor is present [110.15, 215.8, and 230.56]. Figure 110–33


Where the premises wiring system contains branch circuits supplied from more than one voltage system, each ungrounded conductor, where accessible, must be identified by system. The means of identification must be posted at each branch-circuit panelboard [210.5(C)]. Electricians often use the following color system for power and lighting conductor identification:

  • 120/240V single-phase—black, red, and white
  • 120/208V, three-phase—black, red, blue, and white
  • 120/240V, three-phase w/high-leg—black, orange, blue, and white
  • 277/480V, three-phase—brown, orange, yellow, and gray; or, brown, purple, yellow, and gray


Q8. The electrical inspector said that the NEC requires all machines to be listed by UL or other. I didn’t think the NEC applied to machines. Is the inspector correct?

A8. I don’t think so. To me, the NEC is an “installation standard” and it does not apply to the internal wiring of electrical equipment [300.1(B)]. However, 90.7 states that factory-installed internal wiring of equipment need not be inspected except to detect alterations or damage if the equipment has been listed. This does put a heavy emphasis on the listing of equipment, and some states have a specific state law requiring all electrical equipment to be listed.


Q9. Is the space beneath a raised floor in a computer room considered an exposed location?

A9. Yes. Wiring “behind panels designed to allow access” are considered exposed [Article 100].


Q10. Can a power cord be run through the raised floor of a computer room?

A10. Not unless the flexible cord is listed as a Type DP cable having adequate fire-resistant characteristics suitable for use under raised floors of an information technology equipment room [645.5(D)(5)].


Q11. I was told that the bedroom lights aren’t allowed to be installed on an AFCI circuit. Is this true?

A11. No. All 15 or 20A, 120V branch circuits that supply outlets (including lighting and smoke alarm) in dwelling unit bedrooms must be protected by a listed AFCI device [210.12(B)].  


Q12. Can I connect a range hood in a dwelling unit kitchen to the small appliance circuit?

A12. No. The 20A, 120V small-appliance circuit is only permitted to supply the receptacle outlets as per 210.52(B) [210.11(C)(1)]. However, range hoods can be hard wired to a 15 or 20A, 120V circuit, unless the instructions state other wise and cord-and-plug connected range hoods must be supplied by an individual 15 or 20A, 120V branch circuit in accordance with the equipment instructions [422.16(B)(4)(5)].



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  • Q-10 - Not all raised floors in computer rooms are classified as Information Technology Rooms and therfore Article 645 does not necessarily apply to this question.

    Terry L. Schneider
    Reply to this comment

  • I love the questions and answers newsletter Mike! Keep up the great work.

    Reply to this comment

  • Why does the N.E.C. require the smoke detectors to be on the afci circuit in the bedrooms?

    D. Newman
    Reply to this comment

  • Though not specified by code, what color would you use on a the 240 vac, 3-phase "stinger" leg (open delta)?

    Reply to this comment

  • On high voltage applications, your colors are brown, orange and yellow, or brown, purple and yellow. What does purple represent?

    Reply to this comment

  • On #8, Mike wrote: "To me, the NEC is an “installation standard” ..."

    Was that a typo, I trust? A major problem today is too many electricians use the NEC as a good/sufficient installation/practices guide rather than merely as the "safety standard" it is intended to be. Tehre has been a big push by some parties to extend the NEC into a good practices "installation" manual, but it has met with substantial resistance.

    Nick Arpaia - ARMAC Electric
    Reply to this comment

  • Is it acceptable to install a sub-panel in a walk in pantry if all clearance criteria are met. This pantry is approx. 125 sq'

    jim birk
    Reply to this comment

  • Hello. I have a suggestion that may sound silly, but would it be any problem to list all of the answers after all of the questions, and not iimmediately following each one of them? Just a suggestion. Thanks for everything Mike and team, Ed

    Reply to this comment

  • On number 1, the answer is correct that a main bonding jumper shall be installed in service disconnect enclosure based on NEC. But the bonding jumper in meter enclosure shall be removed if a metal conduit is installed between service disconnet and meter can. Otherwise, objectionable current will flow from service disconnect to the meter can.

    Reply to this comment


    Reply to this comment

  • With respect to question 8, some jurisdictions have extended the UL or 3rd party inspection requirement to equipment such as HVAC equipment and, even to manufacturing process tooling when it is connected to the disconnecting means prior to the fitup construction final inspection.

    Lonnie Zlomke
    Reply to this comment

  • On Question #8 - Article 90.2 (A) This Code covers the installation of electrical conductors, equipment, and raceways; siginaling and communications conductors etc.

    Machinery and I use the word loosely depends on what is is, it's function etc. This is what dictates how that piece of equipment is Labeled and Listed. The typical standard used is NFPA-79 but this has it's limitations as well. As for the electrical inspector "The Authority Having Jurisdiction" the state and local codes may require certain types of equipment to be Listed by an NRTL. This is very prevelent on the West Coast and a lot of major citys across the usa.

    If this is the case and and the equipment does requare a Listing /Label from an NRTL this can be done as a field evaluation by UL, ETL, CSA, FM etc. The average cost to have this accomplisher can range from a few thousand to tens of thousands based on how big the job is. Also, there needs to be a field servey by and outside consultant to tell you what needs to be done in order to pass the NRTL field inspection. The NRTL cannot tell you what to correct. This is a conflict of interest. Then the work must be done and the NRTL will do the inspection. based on the inspector this could take several times.

    Mike Dionne
    Reply to this comment

  • Q7: I'm 65 and I was apprenticed by a non-union Journeymen which taught me that 120/208 was Black/Orange/Blue and 120/240 was Black/Red/Blue I later went with the I.B.E.W. which taught the same thing, could both teachers be wrong?

    Barry DeWees
    Reply to this comment

  • Q7: Where can you buy the color coded labels to apply to panels? I

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  • Mike your answer for number 6 suggest that it is ok to ignore the manufacture installation guideline and the NEC. A microwave needs to be installed on a dedicated circuit sized as per the NEC & the manufactures guidelines. We are seeing a lot of "Built In" microwaves being installed in homes where the oven vent hood was. This is almost always on a shared 15 amp circuit. This is done by home owners who are looking to sell their homes with the new upgrades to the home. The new home owner inherits a serious problem. We are seeing a lot of burnt wires, circuit and breakers due to this extreem over load.

    Q6. Can I install a single 15A, 125V receptacle in a kitchen for a microwave only without GFCI protection?

    A6. Well… If it’s a dwelling unit and the microwave is installed in its own dedicated space (not sitting on the counter space), the answer is yes. GFCI protection in a dwelling unit kitchen is only required for 15 and 20A, 125V receptacles that are installed to serve countertop surfaces [210.8(A)(6)]. But, all 15 and 20A, 125V receptacles in commercial kitchens must be GFCI protected according to 210.8(B)(2) even if they are not serving the countertop.

    John K. Erickson
    Reply to this comment

  • On number 8, OSHA requires (29 CFR 1910) that equipment installed be either listed by a NRTL or otherwise certfied as safe by the manufacturer or facility. If the latter, many records must be kept to prove this assertion. UL is not the only nationally recognized test lab (NRTL) that OSHA approves to stamp your equipment. Further, a listed piece of equipment may be listed for something, but not necessarily what or how you are using it. Which standards was it approved for and are you using it properly? More than one product has been listed and bears a bunch of cute little logo stamps, but what was tested and approved has little relationship to implied intended use. And if it breaks, hurts someone, or causes problems, their lawyers will refer you to the fine print disclaimers that the salesman never mentioned.

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