National Electrical Installation Standards

Standards as High as Your Own

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  • June 27, 2019

    Re: CQD answer published June 12, 13 & 21, 2019 - Raceway Fill and Adjustment Factor Just a little help for Bill Neitzel and his search for a conduit fill phone app that does #18 and #16 TFN wires, asked on 06/20/19. I use the app "Conduit Fill Tracker" from "Summit Electric Supply" and it does both #18 and #16 TFN wires. Most wire types like THW, THWN, THHN, etc. will only go down to #14 in the app, but others like TFN, TFFN, XFF, etc. will go down to #18.Richard Cressotti
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  • June 26, 2019

    Is twisting conductors prior to installing the wire nut violating code? Gregory Slack
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  • June 25, 2019

    Type SE cable with an un-insulated neutral conductor is not permitted for hooking up an electric range in a new branch circuit, it is used as a neutral conductor or an equipment grounding conductor. False What's the article?Theodore Raposas
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  • June 24, 2019

    We have an industrial occupancy where single conductors are used in cable tray compliant with NEC 492. Conduit nipples are used at each equipment termination and we have two challenges that we cannot come to agreement on: 1. NEC 250 requires that each raceway carry a fully rated grounding conductor sized per Table 250.122. These are large ampacity feeders with multiple sets of 500kcmil conductors per phase. The installation includes a single ground conductor its entire length through one of several nipples at each termination and in the cable tray. Question: Is a conduit nipple a raceway? I say yes, and therefor NEC 250.122(F)(1) requires that the ground conductor must pass through each conduit nipple (short raceway). This would also be required to comply with NEC 2. These same feeders have unsupported conductors between the cable tray and termination points (gear and busway taps). NEC 392.30(B)(3) allows a max. distance of 6’0” between the tray and the equipment, this is not viewed as a restriction on conductor length. The conductor length between the cable tray and conduit nipple at each busway tap is 6’3”. The conductors are formed into a drip loop arrangement to ensure no water migration into the equipment. All the weight of the conductors rests on the termination lugs of the busway. Question: While this appears to meet all applicable NEC 392 code sections, we feel this is poor installation practice: a) the exposed conductors must be supported; b) bend radius minimums must be maintained over time (sag minimized); c) and the stress on the lug terminations must be eliminated. Thoughts? Gil Martin, PE, LEED AP
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  • June 21, 2019

    Is this code violation. we install 3/4 pvc schl 40 along a wall above damage inspector state date code on material 2/14/14 please remove an install a more up to date material is this allowed?Ivey Rainwater
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  • June 20, 2019

    Re: CQD answer published June 12 & 13, 2019 - Raceway Fill and Adjustment Factor 1) Charlie; There are a number of useful web sites that will calculate the conduit fill. These will allow one to readily change the number of conductors, insulation type and conduit type and size. There also are a number of apps for smart phones. For a web site, I prefer the Racewayfill Calculator on, Unfortunately, the smallest gauge allowed on many web sites is 14 AWG and the few I checked also don't support type TFN insulation. Although it is not stated, I would assume the "dimming" wires are low voltage control wires and they may be Class 1, 2 or 3 circuits. Assuming the "dimming" wires are part of Class 2 or 3 circuits, regardless of the voltage rating of the type TFN insulation, wouldn't mixing low and high voltage wiring in the same conduit be a violation? Andrew H. “Drew” Brejda 2) Hello! Great forum, been following you for years! In response to the answer you gave, shouldn’t 0-10v dimming (I don’t think the electrician specified what classification but I believe most dimming circuits are class 2?) have separation as per 725.136(I)? I really enjoy following every morning! Keep up the great work! Thank you, James Doherty3) Charlie et all, Thanks for the great service you perform for our industry answering the multitude of questions that are presented. As many of us who interpret the Code, it is sometimes easy to focus on the question and forget about the other issues that each installation can present. In response to CQD on 6/11 & 12/2019 I would like to add that the conductors used for dimming could only be installed in the same raceway if they are considered Class 1 and meet the conditions of NEC 725.48(B)(1) and have adequate voltage ratings. NEC 725.48(B)(1) would limit the Class 1 conductors to only be installed in raceways where the Class 1 circuits and the power-supply circuits are functionally associated. The question implies the installer is interested in “loading up the conduit” to the maximum, which would be acceptable if the Class 1 and power-supply conductors are associated, with no other conductors installed. Class 2 and Class 3 dimming conductors would not be allowed in the same raceway with power and light conductor as indicated in NEC 725.136. Keep up the good work. Bill Neitzel
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  • June 19, 2019

    Keep up the good work. I have a new project to an old plant, 1976 construction. The power provided is 480-volt, 3 phase, open delta, B phase grounded, hopefully at the service disconnect. The NEC seems to assume that all 3 phase systems are 4 wire wye. Shouldn’t the ground be separated from the grounded phase to the transfer switch and the B phase treated as any other phase and the ground a separate wire? Should the grounded phase be connected to the line side of the motor starters and continue to the motor? Where in the code is this situation covered? Thanks, Have a good day!!Lowell I. (Laddie) Wolfe Jr.
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  • June 18, 2019

    Re: CQD answer published Monday, June 10, 2019 -Splices in Cabinets Hey Charlie, Noticed that the answer to the question regarding splicing in a panelboard cabinet didn't include allowing for the conductors, splices, and taps. So, we have to include all these components when considering the permitted 75% of the space to be utilized not just the conductors. How about commenting on how one determines the space in the panelboard that is under consideration? In addition, it is common for the wiring space at the sides, top and bottom of the cabinet to differ. Thanks for considering responding to these points, Phil Simmons
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  • June 17, 2019

    In a commercial kitchen, with a sink, I know that all duplex outlets must be GFCI protected. If you install a Simplex outlet, for say a Microwave, does it have to be GFCI protected? Charles Taylor
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  • June 14, 2019

    I recently changed out a furnace/ AC system I discovered the previous HVAC tech, hard word the condensate Pump to the single pole, single box with these he 120 V. Switch, Having cut the end of the 120 v. Condensate Pump and hard wired to the 120 v. Switch for the On / off for the furnace Is this code acceptable? Or does the condensate Pump need to be replaced and a 4”. Square box with switch and receptacle need to be installed? Thank you, Joe
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  • June 13, 2019

    Charlie, I would like your expert opinion regarding cable protection in residential applications. SE cable is allowed indoor or outdoor when it is attached to a building surface, say when connecting a meter base to a disconnect. What is your opinion when connecting to a pad mounted appliance, say an AC condenser or back-up generator. In these instances the cable (SE or other) is not supported in the space between the building and appliance and may be subject to mechanical damage from falling objects. Dave
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  • June 12, 2019

    Raceway Fill and Adjustment Factor Part 2 I need to know how many #10 awg thhn wires and #18 awg dimming wires derated I can fit in a 1" conduit? How would you derate and split up the different wires to know how many we can have in each pipe.Michael Henson
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  • June 11, 2019

    Raceway Fill and Adjustment Factor Part 1. I need to know how many #10 awg thhn wires and #18 awg dimming wires derated I can fit in a 1" conduit? How would you derate and split up the different wires to know how many we can have in each pipe.Michael Henson
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  • June 10, 2019

    First, I've been reading this column for a for many years and have learned a great deal. Keep up the good work! Now, I have a control panel in a Class I, Div. II area. The panel is operating at 24 VDC. Everything in the panel is rated for use in a Class I, Div. II area. Does the conduit entering the panel and at the field devices need sealed? Thanks in advance,Mike, Columbus, OH
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  • June 7, 2019

    Is it ok to splice wire, inside the breaker panel, to move a breaker to a different location in the panel?Arnold Di Gregorio
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ABOUT CQD: The Code Question of the Day (CQD) is NECA and ELECTRICAL CONTRACTOR Magazine’s flagship National Electrical Code (NEC®) public forum for the industry, sponsored by EATON. The daily distribution of Q&A generates a lively dialogue and shares relative Code-based practical responses.

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CHARLIE TROUT: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Even though Charlie passed away in October of 2015, his work continues in spirit. NECA continues to maintain this question forum for its many subscribers in memory and recognition of all his significant contributions to making the NEC what it is today.

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IMPORTANT NOTICE: Unless the question requests a response based on a specific edition, all answers are based on the latest edition of NFPA 70® National Electrical Code®.

This correspondence is not a formal interpretation of the NEC® and any responses expressed to the questions are opinions and do not necessarily represent the official position of NECA, NFPA, the NEC Correlating Committee any Code-making panel or other electrical technical committee. In addition, this correspondence is neither intended, nor should it be relied upon, to provide professional consultation or services. 

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