Clean and dirty circuits sharing a neutral.
- Thread starter heymitduh
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barbeer
Senior Member
- Location
- Pinellas County, FL
I do not believe that we should assume the definition of "clean" and "dirty", maybe you could clarify. There are other factors to consider.........what phase are the ungrounded conductors on.........maybe some more info is needed for a proper response.
- Location
- Logan, Utah
I have heard the terms "clean power" refered to as a circuit that is dedicated for computers and free of loads that might create "noise" in the circuit. The term "dirty power" refered to a circuit that was run to the same area as the "clean power" and used to supply loads that could cause noise and interference on the computer power circuit.
If this is the case in your application, I would recommend using a separate neutral for each circuit to help keep the circuits separate. There is no code requirement for this.
Chris
If this is the case in your application, I would recommend using a separate neutral for each circuit to help keep the circuits separate. There is no code requirement for this.
Chris
mistabass
Member
- Location
- Rhode Island
you also have 2 circuits mwb need 2 pole breaker 210-4 b
- Location
- Logan, Utah
Not necessarily a 2 pole breaker. 210.4(B) requires simultaneous disconnection of both ungrounded conductors of the circuit at the source. Identified handle tie comply with this section as well as a 2 pole circuit breaker.
Chris
dbuckley
Senior Member
- Location
- Canterbury, New Zealand
If you have a clean and a dirty circuit sharing a neutral, then the laws of physics require the neutral to have impedence, and thus your clean circuit is now dirty too.
Seperate neutrals. You might want seperate grounds too.
Seperate neutrals. You might want seperate grounds too.
slc410
Electrician
- Location
- Madison wi
- Occupation
- Electrician
I know now that all circuits are required to have seperate neutrals. Sharing neutrals is no longer permitted. Dont know if that is only in wisconsin but that is the way we have been told for the last couple of jobs. I believe it is a precursor to 2011 code change.
I havn't heard this? Is 2011 NEC going to forbid the use MWB circuits?
- Location
- Logan, Utah
I doubt that the 2011 NEC is going to require a separate neutral for each circuit and prohibit MWBC's.
My guess is that there has been some misinformation going around on the last couple of jobs that you have been on. Most likely someone has misinterpreted 210.4(B) into not allowing MWBC's. It seems like this myth is spreading pretty fast.
Chris
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
There is no statement in the Wisconsin electrical code (Comm 16) prohibiting shared neutrals.
growler
Senior Member
- Location
- Atlanta,GA
There is more to consider than just the NEC when doing electrical work. The NEC will give you the minimum requirements. If the customer is paying for a clean (dedicated circuit ) then that's a job specification. You should give him what is specified on the plans because that's what he's paying for.
You wouldn't want a dedicated circuit for a computer tripping just because someone overloaded a circuit for something else. If they share a neutral the will have a common trip and with a common neutal it won't be clean anyway.
Remember that you can't wire just to code minimum if the customer is paying for above code work ( dedicated circuits).
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
MWBC are still allowed but the NEC has made their use very difficult, so some may elect not to use.
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