This article was posted 10/28/2005 and is most likely outdated.

October NEC Questions and Answers
 

 
Topic - NEC Questions
Subject - October NEC Questions and Answers

October 28, 2005 

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October NEC Questions and Answers

By Mike Holt for EC&M Magazine

Q1. Is GFCI protection required for a 15A or 20A, 125V receptacle that is located within 6 ft of a janitorial closet sink in a commercial building?

A. No. However, GFCI protection is required for all 15 and 20A, 125V receptacles located within 6 ft of a dwelling unit utility sink [210.8(A)(7)].

Q2. How far away must a 120/208V, three-phase panelboard be located from a janitorial closet sink?

A. The panelboard may be installed as close as you would like to a janitorial sink, however a minimum of 36 in. deep by 30 in. wide of clear working space is required in front of the panelboard [110.26(A)].

Q3. I have a facility that contains a small data center for a call center. The CATV, telephone, and satellite dish are individually grounded to standalone ground rods. The designer claims that the individual ground rods are not required to be grounded to the building grounding electrode system. Is this true? 

A. No. The NEC requires all communications systems on or in a structure to be grounded to the building grounding electrode system.

  • Communications Systems (Telephone), 800.100
  • Radio and Television Equipment (Satellite),  810.21
  • CAT, 820.100
  • Network-Powered Broadband Communications Systems, 830.100

The purpose of grounding all systems to the same electrode (basically bonding the systems together) is to reduce differences in potential between communications circuits and the power system during a lightning event.

Q4. What are the NEC requirements for the installation of a transfer switch ahead of the service disconnecting means?

A. A transfer switch is not permitted to be installed on the supply side of the service disconnecting means unless it is rated ‘suitable for use as service equipment’ (transfer switch containing a disconnecting means) [230.66 and 230.82].

Q5. My buddy told me that a GFCI or AFCI protected circuit could not be used to supply power to a GFCI receptacle? Is that true?

A. No, both GFCI’s and AFCI protection devices will operate just fine if supplied by a GFCI or AFCI protected circuit.

Q6. Can a flexible cord with and attachment plug be located below the raised floor of an information technology equipment room?

A. Maybe. Flexible cords under the raised floor of an information technology equipment room are permitted, but the cable must have adequate fire-resistant characteristics suitable for use under raised floors of an information technology equipment room. To meet this requirement, the cable be listed as Type DP (Data Processing) [645.5(D)(5)].

Q7. Can an optional stand-by generator be connected to premises wiring by the use of an extension cord having double male attachment plugs?

A. No. The Code requires all fixed or portable optional standby power systems be connected to the premises via a transfer switch [702.6]. In addition, attachment plugs are not permitted to be installed so their prongs, blades, or pins aren’t energized, unless inserted into an energized receptacle [406.6(B)].

Q8. I came across 120V utility wiring for a metal light pole. I told the lineman that the NEC requires the metal cover of the handhole and metal pole to be bonded so that dangerous touch voltage from a ground fault would be removed by the opening of the circuit protection device. His response… “we are not required to comply with the NEC and that his installation was safe because the metal cover and pole was grounded to a ground rod. Is this true?

A. The lineman is correct that his installation is not required to comply with the NEC [90.2(B)(5)] and he’s right that the National Electric Safety Code (utility code) does not require the metal parts of this installation to be bonded to an effective ground-fault current path with the purpose of clearing a ground fault.

Is the utility installation safe? No. There have been and will continue to be many deaths to individuals making contact to energized metal parts that are grounded to the earth, but not bonded to an effective ground-fault path, as required by 250.4(A)(3).

Q9. Is GFCI protection required for a pool pump motor circuit?
 
A. GFCI protection is not required for hardwired circuits that supply pool pump motors. However, receptacles rated 15 or 20A, single phase, that supply pool pump motors must be GFCI protected [680.22(A)(5)].

Note: The outlet that supplies a self-contained indoor spa or hot tub, a packaged spa or hot tub equipment assembly, or a field-assembled spa or hot tub must be GFCI protected [680.44]. Because this rule applies to all outlets and not just receptacle outlets, the wiring for a hardwired self-contained indoor spa or hot tub, a packaged spa or hot tub equipment assembly would require GFCI protection.

Q10. What type of wiring can I used for 70V speaker circuits? The rear of the amplifying equipment states ‘Class 2 wiring permitted.’

A. Since the amplifying equipment specifies that Class 2 circuit wiring is permitted, you can use any Class 2 cable, or any of its permitted substitutions, in accordance with 725.61.

Q11. Can the disconnecting means for air-conditioning equipment be directly mounted on the air-conditioner equipment?

A. Yes, but it’s not a good idea to mount the disconnecting means over machine data tags [440.14].

Q12. What are the NEC grounding requirements for a satellite dish?
 
A. The metal mast [810.15] for radio and television equipment and it’s lead-in cable via a discharge unit [810.20] must be grounded to the building grounding electrode system in accordance with 810.21.
Grounding of the metal mast and lead-in antenna cable serves to reduce voltage surges (caused by static discharge or nearby lightning strikes) from reaching the center conductor of the lead-in coaxial cable. Because the satellite sits outdoors, wind creates a static charge on the antenna as well as on the cable attached to it. This charge can build up on both antenna and cable until it jumps across an air space, often passing through the electronics inside the low noise block (LNBF) or receiver.

Q13. What size wire and breaker is required for an air-conditioner whose nameplate specifies that the circuit conductor must have a minimum rating of 44A, with overcurrent protection not to exceed 60A. The terminals on the equipment are rated 75°C.

A. The branch-circuit conductors and short-circuit and ground-fault protection device must be sized according to the equipment’s nameplate [110.3(B)]. In this example, a 10 AWG conductor having a rating of 50A at the 75°C column of Table 310.16 [240.4(G)] protected by a 60A circuit breaker or fuse will be fine.

Q14. Can single-pole circuit breakers be used for a multiwire branch circuit that supplies power for office partitions?

A. Yes, provided the individual single-pole circuit breakers utilize handle ties that are identified for the purpose [240.20(B)(1) and 605.6]. A common internal trip circuit breaker could be used for this application as well, but all of the individual branch circuits will open in the event of a ground fault in only one of the circuits.

Q15. Is it a good practice to bond the lightning protection system to the building grounding electrode system?

A. The Code requires the lightning protection system, if provided on a premise, to be bonded to the building or structure grounding electrode system [250.106]. This bonding connection is to minimize the difference of potential between the lightning protection system and the electrical system, which should reduce arcing between metals parts within the building.

Q16. I understand that Type AC cable with an equipment grounding (bonding) conductor is permitted to be used for branch circuits serving patient care areas. Can Type MC cable with an equipment grounding (bonding) conductor be use for luminaires located above 7.5 ft in a patient care area?

A. No. 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 [514.13(A)]. This includes the branch circuits that supply luminaires in patient care areas.

The metal armored sheath of Type AC cable is listed as a suitable ground-fault current path for this application because it contains an internal bonding strip in direct contact with the metal sheath of the cable [250.118(8)].

Typically, the outer metal sheath of interlocked Type MC cable isn’t listed as a suitable ground-fault current path [250.118(10)]. Therefore, Type MC cable of the interlock type, where the outer sheath is not listed as an effective ground-fault current path, is not permitted to supply any branch circuit in patient care areas of health care facilities [517.13].

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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.

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Comments
  • question,an existing home has an electric heating unit in the attic,with one 2 -pole 100 amp breaker intregal to the unit .This unit must be replaced .The new unit has two 2- pole 60 amp breakers intregal to the unit.The existing wire type is #4 xhhw.Can a breaker box be set in attic and the two 60 amp subdived loads be fed from this existing wire ?or must this be fed from individual branch circiuts?

    jeff
    Reply to this comment

  • Don't know if I sent this before...

    Editorial comment: You often use "it's" when you should write "its". The first is a contraction for "it is" and the second indicates possession. But we still know what you mean, and you are doing a great service with your newsletters. Keep up the good work!

    Benjamin Scoville
    Reply to this comment
  • Reply from: Mike Holt   
    I hate it that 'spell check' doesn't catch these errors. I often use 'your' instead of 'you're'... Thanks for the feedback and tolerating my typos and grammer errors. I'll try a little harder.
    Reply to Mike Holt

    Reply from: Jim   
    It's "grammar," not "grammer!" Sometimes you just can't win, eh? :-)
    Reply to Jim


  • I am a little confused about question number 13 if the nameplate says a minimum of 44a then how can you use a ten awg wouldn't it have to be a number 8 that is good for 50 whereas a 10 awg is only good for 35 when used on motors and compressor.


    Reply to this comment
  • Reply from: Mike Holt   
    8 AWG is the proper wire size. Sorry.
    Reply to Mike Holt


  • Re: Answer to Q:13, shouldn't that be a size 8 wire vs. a #10?

    Dana
    Reply to this comment
  • Reply from: Mike Holt   
    Yep...
    Reply to Mike Holt


  • Very informative concerning wide array of questions.

    Les Vass
    Reply to this comment

  • Q13 answer is wrong, it should be #8 copper 75degree chart, protected at 50 amps.Also Q16 answer, if type Mc cable has an equipment grounding(bonding) conductor installed in the cable it would meet 517.13 exception No.2, because the question asked if the luminaire was over 7.5 feet.Please let me know if I'm wrong with either of these, its all about learning!! Thanks, love your web site, keeo up the great work!!


    Reply to this comment
  • Reply from: Mike Holt   
    Q13. Typo.

    Q16. Yes MC cable meets 517.13(B), but not 517.13(A). You must comply with all of 517.13. 517.13(B) only exempts the equipment grounding (bonding) conductor, it's not an exception to 517.13(A).
    Reply to Mike Holt


  • On your heat pump question you state #10 at 50 amps is Ok for the load. I don't believe #10 is rated for 44 amps in the 75 degree column and that would be all the connections would be rated for.

    pat winters
    Reply to this comment
  • Reply from: Mike Holt   
    Sorry typo.
    Reply to Mike Holt


  • On your heat pump question you state #10 at 50 amps is Ok for the load. I don't believe #10 is rated for 44 amps in the 75 degree column and that would be all the connections would be rated for.

    I believe the commeent about patient care area lighting above 7.5 is incorrect also.

    pat winters
    Reply to this comment
  • Reply from: Mike Holt   
    Sorry, typo.
    Reply to Mike Holt


  • Q13. What size wire and breaker is required for an air-conditioner whose nameplate specifies that the circuit conductor must have a minimum rating of 44A, with overcurrent protection not to exceed 60A. The terminals on the equipment are rated 75°C.

    A. The branch-circuit conductors and short-circuit and ground-fault protection device must be sized according to the equipment’s nameplate [110.3(B)]. In this example, a 10 AWG conductor having a rating of 50A at the 75°C column of Table 310.16 [240.4(G)] protected by a 60A circuit breaker or fuse will be fine.

    # 10 AWG protected by a 60 amp fuse will be fine??

    delfa
    Reply to this comment

  • Mike: I have a bit of a problem with your answer to Q 13. On the assumption that the air conditioner's conductors are run in a raceway, the maximum ampacity for #10 in Table 310.16 is 35 Amperes for any of the 75 deg. rated types. The way I read it, #8 is the smallest 75 deg. copper conductor one could use. Am I missing something? (I agree with using a 60A breaker.)

    Heinz Rosen
    Reply to this comment
  • Reply from: Mike Holt   
    Sorry, typo.
    Reply to Mike Holt


  • Hi Mike,

    Just a little comment regarding the October Q&A newsletter: I beleive you made a typing error on the answer for questions #13, instead of #10 AWG it should be #8 AWG.

    Very insterresting, keep it up.

    Thanks

    Marcelo

    Marcelo Zanetti
    Reply to this comment
  • Reply from: Mike Holt   
    You are right! Sorry for the error.
    Reply to Mike Holt


  • The answer to Q1 states that "GFCI protection is required for all 15 and 20A, 125V receptacles located within 6 ft of a dwelling unit utility sink [210.8(A)(7)]".

    This section, however, appears to govern only wet bar sinks that have countertops.

    A "dwelling unit utility sink" (perhaps a free-standing laundry tub) does not appear to be captured by the GFCI protection required in this section.

    Ken
    Reply to this comment

  • *Also emailed (reply) separately to your mailing account

    Hope you all are recovering well after Wilma. Our prayers are with you all down there. My brother down the road in Ft-L has been helping his last employer, National Jets, clean up the mess there at the airfield while waiting for Miami Air to put him back on the flying schedule. Attached below are a couple of corrections for you that you may wish to make before you send your Q&A back out again. A couple of the typos leave your answer dangerously incorrect, so you will probably want to jump on a follow-up quickly. You're welcome, and keep up the good work! Richard A. Sanders Project Engineer 618.998.0075 ph replyto:rsanders@hurst-rosche.com

    ____________________________________ Q7. Can an optional stand-by generator be connected to premises wiring by the use of an extension cord having double male attachment plugs?

    A. No. The Code requires all fixed or portable optional standby power systems be connected to the premises via a transfer switch [702.6]. In addition, attachment plugs are not permitted to be installed so their prongs, blades, or pins aren’t energized, unless inserted into an energized receptacle [406.6(B)].

    What I believe you mean is: A. No. The Code requires that all fixed or portable optional standby power systems be connected to the premises via a transfer switch [702.6]. In addition, attachment plugs are only permitted to be installed in a way that ensures their prongs, blades, or pins are NOT energized unless inserted into an energized receptacle [406.6(B)].

    Q13. What size wire and breaker is required for an air-conditioner whose nameplate specifies that the circuit conductor must have a minimum rating of 44A, with overcurrent protection not to exceed 60A. The terminals on the equipment are rated 75°C.

    A. The branch-circuit conductors and short-circuit and ground-fault protection device must be sized according to the equipment’s nameplate [110.3(B)]. In this example, a 10 AWG conductor having a rating of 50A at the 75°C column of Table 310.16 [240.4(G)] protected by a 60A circuit breaker or fuse will be fine.

    What I believe you mean is: A. The branch-circuit conductors and short-circuit and ground-fault protection device must be sized according to the equipment’s nameplate [110.3(B)]. In this example, an 8 AWG conductor having a rating of 50A at the 75°C column of Table 310.16 [240.4(G)] protected by a 60A circuit breaker or fuse will be fine.

    Q15. Is it a good practice to bond the lightning protection system to the building grounding electrode system?

    A. The Code requires the lightning protection system, if provided on a premise, to be bonded to the building or structure grounding electrode system [250.106]. This bonding connection is to minimize the difference of potential between the lightning protection system and the electrical system, which should reduce arcing between metals parts within the building.

    Q16. I understand that Type AC cable with an equipment grounding (bonding) conductor is permitted to be used for branch circuits serving patient care areas. Can Type MC cable with an equipment grounding (bonding) conductor be use for luminaires located above 7.5 ft in a patient care area?

    A. No. 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 [514.13(A) <517 in 2002, right?>]. This includes the branch circuits that supply luminaires in patient care areas.

    The metal armored sheath of Type AC cable is listed as a suitable ground-fault current path for this application because it contains an internal bonding strip in direct contact with the metal sheath of the cable [250.118(8)].

    Typically, the outer metal sheath of interlocked Type MC cable isn’t listed as a suitable ground-fault current path [250.118(10)]. Therefore, Type MC cable of the interlock type, where the outer sheath is not listed as an effective ground-fault current path, is not permitted to supply any branch circuit in patient care areas of health care facilities [517.13].

    Follow-up "Q16-b", then...and forgive me for not having the 2005 handbook yet...

    Since 250.118(11)b. allows, where listed and identified for grounding, "The metallic sheath...of the smooth or corrugated tube type MC cable." - and since 2002-517.13(A) requires "in accordance with 250.118. Type AC, Type MC, Type MI cable...identified as an acceptable grounding return path." - it would seem that if this type of MC cable is used, the answer to the above question would be "Yes" - so long as there was also the redundant insulated grounding conductor required in 2002-517.13(B). - but NOT if the interlocked-metal-tape type were used. ...is that right?

    Richard Sanders
    Reply to this comment
  • Reply from: Mike Holt   
    Thanks for the feedback, and yes MC cable of the smooth and corrugated tub type could be use.
    Reply to Mike Holt


  • Sorry about the huge text blob below, I didn't realize one of those issues had been beat to death before I hit the "reply" button on the email. Also, you REALLY need to get this "comment submittal" page into a html formatted form, rather than just a text dump, so that comments with line-breaks are formatted in a readable way.

    Rich
    Reply to this comment

  • Q 13 #10 wire is only good for 35 amps at 75c. I see that a # 8 has 50 amps at 75c

    Norman Odeneal
    Reply to this comment

  • I am a wiring inspector in the state of Massachusetts. I came across the same situation as described in Question 8. at a subdivision in the town where I work. But to make matters worse, in addition to not having any equipment ground protection, these light poles did not have any overload or short circuit protection. The circuits were tied directly to the secondary transforms by way of utility company hand holes. Also, the neutral connections were not insulated at the pole.

    I've been doing a search on MGL, and I found MGL166-32 that reads in part, "Such inspector shall supervise every wire over or under streets or buildings in such a city, town or district and every wire within or supplied from buildings and structures subject to the provisions of chapter one hundred and forty-three, and the state building code" I interpret that to mean that the AHJ has jurisdiction over that insulation at least in the state of Massachusetts. Any comments or suggestions will be greatly appreciated.

    Mike, you provide a tremendous service for the electrical industry. Thank you so much.

    Romeo Ethier

    Romeo Ethier
    Reply to this comment

  • Good to see so many people know #10 is not large enough for 50 amps. Just tell them it was a test.

    Jim Schiebrel
    Reply to this comment

  • Regarding "DP" rated cables for raised floor installations: I have found it next to impossible to find DP rated power cords for computer applications. But I have found this write-up that perhaps explains why. http://www.abrconsulting.com/art645-2.htm The short answer is that if the computer room is designed correctly acording to the exceptions of Article 645-2, then DP rated cables are *not* required under the raised floor.

    Philip Pokorny
    Reply to this comment
  • Reply from: Mike Holt   
    The question was in relationship to the use of a power cord under a raised floor, not a low voltage or limited energy cable. The cord is required to be DP rated, and I don't think there is such a cord available. But if the question was in reference to signal or communications cables, then you are right, they are not required to be plenum rated.
    Reply to Mike Holt


  • The answer to question # 13 should be a # 8


    Reply to this comment

  • I am sure I am not the only one to catch this, but it seems you have a typo on Q13 the correct wire size should be 8 awg Thanks for all the good info Mike Bruso

    michael bruso
    Reply to this comment

  • Does a 50 amp single phase hot tub that is fed out of a sub panel require a insulated ground all the way back to the main panel or is it just required back to the sub panel containing the gfci's for the hot tub. The hot tub is rated for 50 amps single phase. A 20 amp gfci and a 30 amp gfci will feed the hot tub out of the subpanel. Also is # 8 awg copper large enough to feed the 50 amp circuit or should I use # 6 awg copper?

    rich in arlinton
    Reply to this comment
  • Reply from: Mike Holt   
    Sorry, but this is not the forum to ask questions. If you have a question, please visit www.MikeHolt.com, and post your question on the Code Forum.
    Reply to Mike Holt


  • You may have seen this already. AOL news item.

    http://aolsvc.news.aol.com/news/article.adp?id=20051030192209990001&ncid=NWS00010000000001

    Rich Henes
    Reply to this comment

  • Thank you for your reply in regards to DP rated power cords.

    What about this comment

    > Article 645 Information Technology Equipment > > 12-61 > 645.5 Supply Circuits and Interconnecting Cables. > (D) Under Raised Floors. > (5) DP Rated Cables. New reference added to clarify when power cords installed under a raised floor in an Information Technology Room are not required to be DP rated.

    found on this posting at MikeHolt.com?

    http://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/Significant-Proposals-for-2005-NEC-Part-XIII~20040323.php

    Does that mean that in the future, DP rated cables would *not* be required?

    Philip Pokorny
    Reply to this comment
  • Reply from: Mike Holt   
    This was a proposal for the 2005 NEC which did not pass. So all cords must be DP rated, and there is no such cord...
    Reply to Mike Holt


  • In response to question #13, I am having trouble with number 10 wire being rated for 50A. If i misread this please forgive me but could you please explain.

    Austin
    Reply to this comment

  • Question #13 would be a #8 conductor.

    Bob Hollingsworth
    Reply to this comment

  • Great service, Mike! Hope you're well recovered from Mother Nature. Stay well. K.

    Dick Kaiser
    Reply to this comment

  • Did you notice the error in the answer to question 13 in the October NEC Questions and Answers? A # 8 AWG conductor rated at 50 amps is required not a 10 AWG which is only rated at 35 amps in Table 310.16.

    Mike Cahill
    Reply to this comment
  • Reply from: Mike Holt   
    Yes
    Reply to Mike Holt


  • Your reply to question 16 does not mention Type MC cable having a continuosly corrugated armor. An aluminum continously corrugated armor would satisfy the requirements of 250.118(10).

    John Cancelosi
    Reply to this comment

  • In Q16, he can use hospital grade MC right?

    Will Carpenter
    Reply to this comment
  • Reply from: Mike Holt   
    There is not such thing as 'hospital grade' MC. What is often called 'hospital grade MC' is actually Type AC cable with an insulated equipment grounding (bonding) conductor.
    Reply to Mike Holt


  • Should the wire size for answer #13 be #8

    Marty Gerdes
    Reply to this comment
  • Reply from: Mike Holt   
    Yes
    Reply to Mike Holt


  • In the answer to question #13 it states that the wire size used is 10 AWG. Is this correct? I would never consider the use of 10 AWG in any circuit exceeding 30 amps.

    Q13. What size wire and breaker is required for an air-conditioner whose nameplate specifies that the circuit conductor must have a minimum rating of 44A, with overcurrent protection not to exceed 60A. The terminals on the equipment are rated 75°C.

    A. The branch-circuit conductors and short-circuit and ground-fault protection device must be sized according to the equipment’s nameplate [110.3(B)]. In this example, a 10 AWG conductor having a rating of 50A at the 75°C column of Table 310.16 [240.4(G)] protected by a 60A circuit breaker or fuse will be fine.

    Jimmie Stewart
    Reply to this comment
  • Reply from: Mike Holt   
    Typo.
    Reply to Mike Holt



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