I have 2 6/2 with ground cables installed in my attic. I got a oven that requires a 4 wire (2 hots, 1 neutral, 1 ground). Is it code to utilize the 2 insulated conductors off of 1 nm cable and 1 - off of the other as my neutral?

I would install on neutral bar in panel, make the final splice in a jbox then just extend the correct 4 wire to the oven connection. I do not think it is code but cannot find the scenario in which it rejects that. I do not have access to get to the panel from the oven and want to utilize the existing wiring i have i place if possible. I know it would work, but is it code, and what are the dangers?

  • Hello, and welcome to Home Improvement. I've fixed your question so it is no longer shouting; hopefully the electrical pros here will give you a good answer. – Daniel Griscom Feb 13 '19 at 23:32
  • We the wires installed before 1989? Are they UF? – Harper - Reinstate Monica Feb 13 '19 at 23:47

Nope -- this violates the intent of 300.3(B)/300.20(B)

Trying to "split" a circuit's conductors among cables or raceways is generally prohibited by NEC 300.3(B), with a few exceptions (that are not applicable to typical residential wiring, even if they appear so at first glance).

The issue is that if you have current going out to the load on one wire and back on another, the resulting loop generates a magnetic field within it. This is a EMI hazard as it can induce 60Hz noise into sensitive devices (old tube TVs and monitors were the most common examples), but more importantly, it's a fire hazard because that magnetic field can go on to induce eddy currents into ferrous objects within that loop, heating them up just like a pan on an induction cooktop.

As a result, you're better off running a new 6/3 cable for the new oven, as sadly, there is no such thing as a 240V-only wall oven that I have found listed for US use, and the old-style 3-wire connections are prohibited for new wiring for very good reason.

  • Only the ground can be separate I agree.+ – Ed Beal Feb 14 '19 at 0:20

No,you can't, for reasons ThreePhaseEel describes well. Another side effect of EMI is the cast magnetic fields can make the wires move. It might be audible, it might not. Either way, the repeated 60Hz motion will cause metal fatigue in the wires, causing them to become brittle, crack or snap, causing either localized overheating, or series arc faulting. Both of which can start fires inside the walls where it's impossible to get a hose.

That oven

Take a close look at the schematic of the oven. The oven itself only needs 240V. 120V is for the light bulb, and possibly controls. If it is indeed only the light bulb, put the neutral on the opposite pole instead, and use a 240V bulb.

  • Some ovens are really annoying and use 120V for other internal functions as well... – ThreePhaseEel Feb 16 '19 at 0:28

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