National Electrical Installation Standards

Standards as High as Your Own

Tuesday, January 3, 2017


Good Day, I came across a house that only several rooms were being remodeled. The existing electrical material that they are replacing, in the remodel areas only, is Knob-and-Tube. The homeowner doesn't want to replace the rest of the wiring. Is there a way one can tie the old Knob-and-Tube circuits into an updated 200 amp panel? Thanks Doug



Hey Doug thanks for your question. Yes, Knob and Tube wiring is allowed to be used to extend existing installations as stated in 394.10(1). Notice it is not allowed to be "enveloped" in insulated hollow spaces as stated in 394.12(5) and must be spliced as stated in 394.56 and supported as stated in 394.30(A). A box is not required for splices as the wording in 300.15 only includes outlet and switch points but a box or fitting could be used as stated in 300.16(A) and NM cable could also be used for the extension. Check with the AHJ to see if they have any concerns or if there are any local requirements.

You might want to explain to the homeowner that there is no equipment grounding conductor installed with the knob and tube wiring so replacing the rest of the wiring with a more modern method does have advantages including providing additional receptacle outlets.


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  5. debra | Jan 07, 2017
    You cannot use it again. The building must be very old. It’s better not just to change the knob because it may affect the total wiring. Don’t get the whole place burned. Make the owner understand that replacing with new technologies will only be beneficial to the building. private louvre museum tour
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