NEIS: Code Question of the Day

NEIS: Code Question for Thu, 9 Feb 12

Thu, 9 Feb 12 00:00:00

Subject: CQD January 25, 2012 Charlie, I believe you missed an important point when you told the questioner that table 310.15(B)(7) could be used for dwelling feeders. Very little in the code is that simple. The questioner says that the feeder is to a "lighting panel" in a dwelling. From this, I infer that this panel does NOT supply all loads in the dwelling. 310.15(B)(7) only applies if the feeder serves "all loads that are part or associated with the dwelling unit." Unless this feeder serves all of the loads in the dwelling the questioner will have to use 310.15(B)(16) - formerly 310.16. Donald Haskin Program Coordinator, Skilled Trades The College of Southern Maryland

NEIS: Code Question for Wed, 8 Feb 12

Subject: Re: NECA-NEIS Code Question of the Day - Wednesday, January 25, 2012 Hey Charlie, Thank you for sharing your wealth of knowledge with us and also thanks to everybody that participates. My question is if you install a sub panel and place a disconnect for the sub panel between the main panel and the sub panel does the main panel now become a sub panel also? Thanks Tommy Local 164

Answer:

Hi Tommy, thanks for participating. I'm not sure I understand your question. But I'll try. The NEC does not use the term subpanel. It's just another panelboard fed from another panelboard. Generally you will not find a disconnect “between” panels. A circuit breaker in one panel may be used to feed another panel. I guess “electrician talk” does not always match-up with “Code” talk but the accurate use of Code language always helps. Thanks again for commenting.

Source: Charlie Trout

ANSWERS: Answers are the author's opinions and do not represent formal interpretations of the National Electrical Code.

All answers are based on the latest edition of the NEC, unless the question requests a response based on a specific edition.

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ABOUT THE AUTHOR: Charlie Trout is a nationally-known NEC expert and author. He served on three different National Electrical Code-Making Panels and is past chairman of CMP-12. He is also a member of the NECA Codes & Standards Committee. In 2006 Charlie Trout won the prestigious Coggeshall Award, given to recognize outstanding contributions to the electrical contracting industry in the technical and training area.

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NEIS: Code Question for Wed, 8 Feb 12

Wed, 8 Feb 12 00:00:00

NEIS: Code Question for Tue, 7 Feb 12

Subject: CQD January 31, 2012 Hi Charlie, In response to your answer to Jan 31, 2012 CQD I am not sure if your answer was enough. The Question asked “when multiple circuits are brought”. I assume they mean circuits supplied from different breakers. Where your answer as usual is spot on, in the reference to a device connection arrangement in nonmetallic boxes of 250.148[D], it seems the question is on connecting the EGC together for all circuits in the box. To clarify, this was required as seen in 1999 NEC 250-148, “Where more than one EGC enters a box, all such conductors shall be spliced…” this was removed in the 2002 edition where wording of 250.148 was changed to “…any separate EGC associated with those circuit conductors shall be spliced…”. So while it was clear before to splice “all”, now you need to interpret which conductors are ‘associated' with which circuit, and it would appear as an example, 2 separate circuits, to 2 separate switches, in a 2 gang nonmetallic box, need to terminate at their device, but not also tied to each different circuit. [Code nerd note; in both the ROP and ROC neither make any mention to why ‘all' was changed with ‘associated', only reference metal boxes.] It was nice to see you and Mike working hard in Hilton Head Last week and warm Ft Smith getting closer each day. Steve Froemming

Answer:

Hey Steve, thanks for commenting. Always good to get a little history behind Code requirements. However 250.148 is quite clear. Where circuit conductors are spliced within a box or terminated on equipment within a box, any equipment grounding conductors associated with those circuit conductors shall be connected within the box or to the box. So when multiple circuits are brought into a nonmetallic box or a metallic box the equipment grounding conductors must be connected together in the box.

Section: 250.148
Source: Charlie Trout

NEIS: Code Question for Tue, 7 Feb 12

Tue, 7 Feb 12 00:00:00

NEIS: Code Question for Mon, 6 Feb 12

Subject: Re: CQD Tuesday, January 31, 2012 What about the Exception in 250.148? It seems that it would not be necessary to splice the individual EGCs together. EGCs brought in and connected to their devices individually seems to satisfy (D) also. Always good to have this brain stimulation in the morning, thanks Charlie. Scott

Answer:

Hey Scott, thanks for commenting. Section 250.146(D) applies only to isolated grounding equipment grounding conductors, while 250.148 applies to all other branch circuit equipment grounding conductors (wire types). Removal of the device should not break the required equipment grounding conductor continuity (250.148(B).

Section: 250.146(D), 250.148
Source: Charlie Trout

NEIS: Code Question for Mon, 6 Feb 12

Mon, 6 Feb 12 00:00:00

NEIS: Code Question for Fri, 3 Feb 12

Charlie, Thanks for the great NEC question service. I have a 460-volt, 3-phase motor rated 50 HP and the nameplate current is 58.5 amperes. The motor will run continuously in an exhaust fan application. I have installed three No. 6 THWN conductors in a 1-inch conduit for this motor. The HVAC installer indicated that on the last job, the electrician installed No. 4 AWG THWN to feed this motor. Table 310.15(B)(16) indicates that No. 6 THWN conductors are good for 65 amperes. Which is the minimum correct size conductor for this motor? Thanks in advance. Sam Jenkins

Answer:

Hey Sam, Happy motoring, so they say. Well based on the information in your question, it appears the 6 AWG THWN conductors are too small. Section 430.22 requires conductors for a single motor to be sized at not less than 125% of the motor FLA values based on Table 430.250. Table 430.250 indicates that a 50-HP, 460-volt, 3-phase motor draws 65 amperes. Multiply 65 amperes by 125% and the minimum conductor size required has to be capable of handling 81.25 amperes. Using Table 310.15(B)(16), a minimum of 4 AWG THWN copper wire (85 amperes) is required. Also keep in mind this response does not factor in any conductor ampacity correction or adjustment factors that may also be needed. Note that the temperature rating of the terminations can impact the ampacity of this motor branch circuit. The 6 AWG THWN conductors are too small based on the information provided in the question. Hope this is helpful.

Section: 430.6, 430.22, Table 430.250, Table 310.15(B)(16), 110.14(C

NEIS: Code Question for Fri, 3 Feb 12

Fri, 3 Feb 12 00:00:00

NEIS: Code Question for Thu, 2 Feb 12

Charlie, I am a big fan of the Code Question of the Day. I truly appreciate the way you manage all of these good questions and the silly ones too! Here's my question. My inspector has red-tagged my residential project saying that the insulation in the attic cannot be in contact with the recessed fixtures I've installed. He indicated there must be at least 3 inches of clearance all around and no insulation installed above the fixture. The fixtures are listed and marked “IC” rated. Am I missing something or is this inspector requiring something above Code minimum. Thanks for your help. Bill Maddox

Answer:

Hi Bill, Thanks for participating. Section 410.116(B) covers installations of recessed fixtures and clearly indicates that if the fixture is marked “Type IC” then thermal insulation can be in contact with the fixture. You may have to show the marking on the fixture and the section of the Code that specifically permits thermal insulation to be in contact where so identified. The inspector has the responsibility for interpretations and approvals of installations as provided in 90.4. Sometimes the electrical contractors and electricians have to help them get it right.

Section: 410.116(B)

NEIS: Code Question for Thu, 2 Feb 12

Thu, 2 Feb 12 00:00:00

NEIS: Code Question for Wed, 1 Feb 12

Subject: CQD - January 26, 2012 Good Morning Charlie, better to ask dumb questions, than to get a dumb violation. Jim Metzler

Answer:

Hey Jim, great words of wisdom. Good suggestion for all of us.

Source: Charlie Trout