Sharing Neutral Wire

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  #1  
Old 06-18-07, 07:26 AM
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Sharing Neutral Wire

I am rerouting wiring in a bathroom remodel. My house was built in 1962. I have 200 amp service (sqare D breakers) with the original wiring done in metal conduit. I have 3 separate circuits coming into a junction box through conduit directly from the panel. I am rerouting with Romex and grounding to the boxes. Circuit One is 2 red (220) wires which feed a water heater, Circuits Two and Three are 2 black wires each on separate circuits and one white wire. Question - Can I use the single white wire as a neutral for both circuits Two and Three?
 
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  #2  
Old 06-18-07, 07:40 AM
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If and only if the two circuit breakers are from opposite legs of the incoming 240 volts. That is, the voltage between the two hot wires is 240 volts, and not 0 volts.

There are other requirements for a multi-wire circuit that must be followed as well. Unless you completely understand them, or are wiling to learn about them, I recommend you run normal (non multi-wire) circuits.
 
  #3  
Old 06-18-07, 09:06 AM
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One hot black wire is from circuit breaker #16 and the other hot black is from circuit breaker #34. The original wiring is in conduit running to a light junction box in the ceiling and then spliting off to the separate runs. The original wiring had the white neutral tied to both runs. When I tested the wires in the junction box, they separately tested 110 with the neutral or ground. The 2 hots tested together registered 240. If there is more I need to learn first, I am willing to.
 
  #4  
Old 06-18-07, 09:11 AM
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Circuit breaker numbers are meaningless. Different panel manufacturers number their panels differently.

If you measure 240 volts between the hot wires than you have opposite legs.

Describe the circuit after the panel. Does it split to two separate circuits? Does it remain multi-wire? What devices do you plan to use on it? How do you intend to wire those devices?
 
  #5  
Old 06-18-07, 10:02 AM
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2 hot black wires (separate circuit breakers) and one white neutral enter into the junction box from the panel. There are 2 white wires tied to the one from the panel. Those wire then split off to separate runs with one black and one white wire. They feed lights and wall recepticles in different areas. I was debating using one of the circuits as a single circuit for a new jacuzzi motor as opposed to running a complete new line. or I may run a new line anyways, but still had the question about the shared neutral. Even if I run a new circuit for the jacuzzi, I will still want to use the other for lights and recepticles.
 
  #6  
Old 06-18-07, 10:11 AM
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What you propose is fine. Once you make the split to two circuits you are fine.
 
  #7  
Old 06-19-07, 05:49 AM
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thank you for your help
 
  #8  
Old 06-19-07, 07:45 AM
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Given that your original wiring is in conduit, are you perhaps in a location that _requires_ conduit?
 
  #9  
Old 06-19-07, 08:39 AM
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To prevent future misunderstandings by someone not familiar with what you did I would suggest if the breakers aren't side by side you rearrange them so they are (and still measure 240v) and either use a bar to tie the handles or replace with a 240v breaker.
 
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