Different Circuits Sharing A Neutral

 
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Old 01-19-2009, 07:45 PM   #1
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Different Circuits Sharing A Neutral


Is it common practice when using conduit to have neutrals from different circuits tied together in an electrical ceiling light box instead of running to the breaker box as separate runs?


Jim
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Old 01-19-2009, 08:09 PM   #2
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Re: Different Circuits Sharing A Neutral


No, but are the circuits on separate phases?

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Old 01-19-2009, 08:10 PM   #3
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Re: Different Circuits Sharing A Neutral


Sure...saves a ton copper [which = $$$]...but only if you know what you are doing.
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Old 01-19-2009, 08:52 PM   #4
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Re: Different Circuits Sharing A Neutral


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Originally Posted by Hidyusbeast View Post
No, but are the circuits on separate phases?
Total of three circuits so two are on one phase the other is not. How bad is this? Any problems that would require having the house looked over more closely? The house was built in 04.

Jim
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Old 01-19-2009, 09:16 PM   #5
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Re: Different Circuits Sharing A Neutral


If you are asking this question, how do you know that there is a "Phase Bump" occurring?
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Last edited by MALCO.New.York; 01-20-2009 at 07:05 AM.
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Old 01-19-2009, 09:51 PM   #6
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Re: Different Circuits Sharing A Neutral


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Originally Posted by MALCO.New.York View Post
If you are asking this question, how do you know that there a "Phase Bump" occurring?
Maybe I don't. It is my understanding that the two feeds coming into the box are at different phases, and that a 220 breaker would be coming off the two phases. The hot wires going through the conduit are fed from three breakers all in a row one above the other. Please correct me if I am wrong.

Jim
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Old 01-19-2009, 10:32 PM   #7
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Re: Different Circuits Sharing A Neutral


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Originally Posted by paintr56 View Post
Maybe I don't. It is my understanding that the two feeds coming into the box are at different phases, and that a 220 breaker would be coming off the two phases. The hot wires going through the conduit are fed from three breakers all in a row one above the other. Please correct me if I am wrong.

Jim

What is it that the Plumbers always say???????

Call your Electrician. He will know!!!!
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Old 01-20-2009, 06:35 AM   #8
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Re: Different Circuits Sharing A Neutral


Put an Arc Fault Breaker on that cir. and see what happens
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Old 01-20-2009, 07:04 AM   #9
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Re: Different Circuits Sharing A Neutral


Quote:
Originally Posted by Hidyusbeast View Post
No, but are the circuits on separate phases?
Quote:
Originally Posted by paintr56 View Post
Total of three circuits so two are on one phase the other is not. How bad is this? Any problems that would require having the house looked over more closely? The house was built in 04.

Jim
?????????????????????????????????????????????????? ???????????????????
What are you guys talking about????? Seperate phases???? A 3 phase house? Do you Know???? Hire a real electrician instead of trying to figure it out yourself or by such an errant answer here.................
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Old 01-20-2009, 07:20 AM   #10
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Re: Different Circuits Sharing A Neutral


Quote:
Originally Posted by paintr56 View Post
Is it common practice when using conduit to have neutrals from different circuits tied together in an electrical ceiling light box instead of running to the breaker box as separate runs?


Jim
Yes it is common, legal, acceptable and safe for more than 1 circuit to share a neutral, look it up in NEC.

Dedicated circuits will have their own neutral and ground.

If you are having problems and don't understand electricity call a licensed electrical contractor.
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Old 01-20-2009, 09:33 AM   #11
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Re: Different Circuits Sharing A Neutral


Quote:
Originally Posted by paintr56 View Post
Maybe I don't. It is my understanding that the two feeds coming into the box are at different phases, and that a 220 breaker would be coming off the two phases. The hot wires going through the conduit are fed from three breakers all in a row one above the other. Please correct me if I am wrong.

Jim
Where are you located Jim?
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Old 01-20-2009, 04:40 PM   #12
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Re: Different Circuits Sharing A Neutral


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Originally Posted by mrmike View Post
?????????????????????????????????????????????????? ???????????????????
What are you guys talking about????? Seperate phases???? A 3 phase house? Do you Know???? Hire a real electrician instead of trying to figure it out yourself or by such an errant answer here.................

I was thinking the same thing. Triple phase in a house? I have seen it before (Short Hills, NJ), but it is very rare.
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Old 01-20-2009, 04:45 PM   #13
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Re: Different Circuits Sharing A Neutral


Quote:
Originally Posted by paintr56 View Post
Is it common practice when using conduit to have neutrals from different circuits tied together in an electrical ceiling light box instead of running to the breaker box as separate runs?


Jim

Think of it this way.... if a normal single-family dwelling has a 3-wire service (two ungrounded, one grounded), then a 3-wire circuit within the dwelling is suffice. The same rules apply for a 4-wire Wye (208/ 120 VAC), where a single neutral is used as a common point for each of the phase conductors. There are others used in the industry but this should hopefully answer your question.
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Old 01-20-2009, 05:19 PM   #14
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Re: Different Circuits Sharing A Neutral


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Originally Posted by bwalley View Post
Yes it is common, legal, acceptable and safe for more than 1 circuit to share a neutral, look it up in NEC.

Dedicated circuits will have their own neutral and ground.

If you are having problems and don't understand electricity call a licensed electrical contractor.
I think I may have offended some of you by asking a question. I am not having a problem. I found this while changing a light fixture and I have never seen it before. I just asked if this was reason to call in an electrician or if it was normal.

Jim
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Old 01-20-2009, 05:29 PM   #15
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Re: Different Circuits Sharing A Neutral


Quote:
Originally Posted by paintr56 View Post
I think I may have offended some of you by asking a question. I am not having a problem. I found this while changing a light fixture and I have never seen it before. I just asked if this was reason to call in an electrician or if it was normal.

Jim
I may have misunderstood you.

Are you having a problem with the circuit?

Or did you just see something you thought was odd?
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Old 01-20-2009, 05:39 PM   #16
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Re: Different Circuits Sharing A Neutral


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Originally Posted by Magnettica View Post
I was thinking the same thing. Triple phase in a house? I have seen it before (Short Hills, NJ), but it is very rare.

It's a lot more common than one would think... Watchung, Weehawken, even Jersey City [think hi-rise condos...dual floor units w/private elevators]
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Old 01-20-2009, 05:42 PM   #17
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Re: Different Circuits Sharing A Neutral


Quote:
Originally Posted by paintr56 View Post
Is it common practice when using conduit to have neutrals from different circuits tied together in an electrical ceiling light box instead of running to the breaker box as separate runs?


Jim
What needs to be determined is:
- Do we have 1 - 2 - 3 or more circuits sharing the neutral?
- Is the service 1 or 3 ?

Simply because a box has several wires in it, that is not a clear indication of the number of circuits in the box.
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Old 01-20-2009, 07:20 PM   #18
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Re: Different Circuits Sharing A Neutral


Yes, if 3 circuits are sharing a single neutral on a 1 (single phase) service then that neutral would carry the sum of 2 of the ungrounded conductors and the difference of the other 2 pairs not on the same phase.

Getting all this Jim?
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Old 01-21-2009, 12:02 AM   #19
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Re: Different Circuits Sharing A Neutral


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Originally Posted by Celtic View Post
What needs to be determined is:
- Do we have 1 - 2 - 3 or more circuits sharing the neutral?
- Is the service 1 or 3 ?

Simply because a box has several wires in it, that is not a clear indication of the number of circuits in the box.
We have 3 circuits coming off of two legs in a single phase system. The three breakers are locate one above the other.

I seem to have confused things when I mentioned two phases. I thought the two legs were 180 degrees out of phase. When Hidyusbeast asked if the circuits were on one phase or two I thought he was talking about the two legs.

Jim
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Old 01-21-2009, 12:18 AM   #20
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Re: Different Circuits Sharing A Neutral


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Originally Posted by Magnettica View Post
Yes, if 3 circuits are sharing a single neutral on a 1 (single phase) service then that neutral would carry the sum of 2 of the ungrounded conductors and the difference of the other 2 pairs not on the same phase.

Getting all this Jim?
I think I am getting about 80% of it. When you say not on the same phase am I correct in thinking you are talking about feeding off of separate legs?

From what I am reading about the nec shared neutrals are called common neutrals and code calls for them to be fed from separate legs to balance the load. Not sure if balance is the correct term. When sharing the same leg the capacity of the neutral could be exceeded.

Jim

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