National Electrical Installation Standards

Standards as High as Your Own

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Tuesday, November 13, 2018

Question:

Thank you from everybody that uses or works with electricity for carrying on Charlie's noble cause. While installing generators connected to the entire electric service of homes that were wired under older codes, we encounter dryer, range and oven circuits that were wired under an old code method that did not require a separate insulated neutral. When properly connected under the old wiring method, there is a bond jumper between the uninsulated grounded conductor and the frame of the appliance, at the appliance. When a disconnecting means, such as a service rated transfer switch, is installed in the feeder between the meter and the main breaker or split buss panel, the neutrals and the grounds in the panel must be separated, and any bond jumpers between the neutral block and ground must be disconnected. Since in some cases there is a 120 volt control circuit, or appliance lights connected to the grounded conductor and a phase conductor within the appliance, a dilemma is created. In many cases it is very impracticable to run an entire new circuit which would disturb existing wall and ceiling finishes and require extensive patching and painting, the dilemma is this- is the uninsulated conductor to be treated as a ground, or a neutral, and to which location in the panel (that has now become a "sub-panel") should this uninsulated conductor be connected? This may be a question with no good answer, but I am interested in your comments.

John Kahler

A

Answer:

Hey John thanks for your question and the kind words. There is an answer but you might not like it. Uninsulated grounded conductors are allowed for existing ranges, wall mounted ovens, counter mounted cooking units, and clothes dryers if SE cable is used - and it originates from service equipment as stated in 250.140 Exception (3). The transfer switch installed upstream of the original service equipment becomes the new service equipment in you example therefore the grounded conductor must be insulated. If the existing installation was not modified it can remain if it meets all of 250.140 Exception but adding the transfer switch on the line side of the previous service equipment creates the violation. It can involve some patching and refinishing of surfaces for installation of a new cable but needs to be done.

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ABOUT CHARLIE: 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. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.

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