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Old 06-27-2011, 08:31 PM   #16
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2 way switch mystery.. no power at switch but power at light when turned on


so is a 3 conductor cable used for 2 breakers used often?

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Old 06-27-2011, 09:20 PM   #17
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2 way switch mystery.. no power at switch but power at light when turned on


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so is a 3 conductor cable used for 2 breakers used often?
Yes. This is called a "multi-wire branch circuit" or MWBC. The two breakers must be on different hot legs, so the two hot wires have 240V between them and the neutral wire only carries the difference in current between them. Until recently, two completely separate circuit breakers could be used on a MWBC and there would not necessarily be any indication on the panel that it was wired that way. This led to some safety issues when servicing, since turning off one circuit breaker but not the other would not make it safe to disconnect and work on the neutral conductor. So nowadays the NEC requires that MWBC's be wired only with adjacent circuit breakers that have a the breaker handles tied together so they can only be turned off simultaneously.
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Old 06-27-2011, 10:13 PM   #18
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2 way switch mystery.. no power at switch but power at light when turned on


so if i want to draw power from one of the hots for a bathroom light/ bathroom fan, can i still use the white as neutral?
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Old 06-27-2011, 10:25 PM   #19
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2 way switch mystery.. no power at switch but power at light when turned on


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so if i want to draw power from one of the hots for a bathroom light/ bathroom fan, can i still use the white as neutral?
Not only can you, you have to. What else would you use?

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