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3 wire to 4 wire feeder repair


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I'm trying to figure out if it's okay to just run an additional single wire instead of a completely new 4 wire feeder for a sub panel that was originally feed with a 3 wire feeder from the main disconnect at the meter. 

There's a group of newer home (4-6 years) built where all the feeder wires from the main disconnect at the meter to the sub panel inside the home were all ran with 3 wire feeders. The builder has agreed to repair them all which will not be an easy task. There will be a lot of drywall cut out to chase the new wire from the meter on one side of the home to the sub panels on the other side of the home. The electrician and builder plan to run one single wire form the main disconnect to the sub panel to isolate the equipment ground and neutral wires inside the sub panel. Should there be a whole new 4 wire feeder ran?



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I don't see a problem with it as long as it's the EGC because the EGC is not a current-carrying conductor like the other three.  There wouldn't be any issue with magnetic fields inducing currents in nearby conductive materials as long as there's no ground short anywhere.  I'd check with the AHJ first to be sure though.

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Bill and Jim thanks!


What about 300.3(B)(3)? Would it be an exception? The Feeder from the Meter to the sub panel is NM ran inside the wood framed walls. No conduit or raceways between the two. 

NEC 300.3(B) requires all conductors of the same circuit to be contained in the same cable—unless otherwise permitted in accordance with 300.3(B)(1) through (4). NEC 300.3(B)(3) permits conductors in wiring methods with a nonmetallic (NM) sheath to be run in different cables. NEC 300.3(B) requires all circuit conductors of an individual circuit to be grouped to reduce inductive heating. This is not a problem with nonferrous wiring methods 

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