Mike Stewart
Member
Can someone help me understand this article, the way it is being explained is that for every "hot" you have to have a neutral, or you can install a three pole breaker, have three hots and one neutral.
Articel 210.4
- Thread starter Mike Stewart
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Mike Stewart
Member
The engineer is on record is wanting to use breaker ties but the customer engineer says two more neutrals have to be installed so that all three hots has its own neutral. Our local inspector says it refers back to this code but I guess I am not fully understand the code.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
In some situations you may want individual neutrals but the code clearly allows a neutral for a multiwire branch circuit. As stated by Roger you can use a 3Pole breaker or sp breakers with handle ties.
If MWBCs weren't allowed any more, they would have been written out of the Code. But clearly, they're still there, so they are allowed.
210.4 merely states how MWBCs are to be handled.... it doesn't say you can't have them.
If MWBCs ever become 'illegal', I don't know what we'll do to supply power to all these residential electric ranges, cooktops, ovens and clothes dryers.
210.4 merely states how MWBCs are to be handled.... it doesn't say you can't have them.
If MWBCs ever become 'illegal', I don't know what we'll do to supply power to all these residential electric ranges, cooktops, ovens and clothes dryers.
Mike Stewart
Member
But is it required to use either the three hots with three neutrals "or" a three pole breaker or single poles with a breaker tie?
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Or a house.
Poor examples of the MWBC the OP is referring to. Those are two pole ckts to individual UL listed units which MUST be run on two pole breaker, no exceptions (residential), maybe three pole for commercial.
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Read the definition of a MWBC:
Branch Circuit, Multiwire. A branch circuit that consists of two or more ungrounded conductors that have a voltage between them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system.
All the circuits I listed fit that definition.
Actually those are good examples of MWBC's regardless of what is connected to them.
Roger
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
3 ungrounded and 3 grounded conductors sounds more like 3 regular circuits than a MWBC. One of the main reasons for a MWBC is to save on wire. If the 3 ungrounded conductors are feeding different outlets why not just use 3 individual breakers? I wouldn't want one circuit tripping and shutting the other two down. IMHO!
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
With handle ties you likely wont have that happen, but also you might not know which one tripped as the other two will hold the handle in the on position and not let it go to the middle.
I believe the OP should let the customer and the engineers Battle this out, as this is a design choice not an installation problem, as was said it can be done 3 ways.
I simply stated they where poor examples of MWBC that the OP was referring to (he is talking about 2 or more single pole ckts sharing a neutral, not a two pole dryer ckt)
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Take the dryer for example, it utilizes a two pole MWBC and can use handle ties or a multi-pole breaker, a "two pole" breaker is not mandatory for this circuit, see 240.15(B)(2)
Roger
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- Location
- New Jersey
- Occupation
- Journeyman Electrician
Yes.
It would than be legal to run a 10/4 to the dryer and grab a 20 amp MWBC off the dryers nuetral and handle tie the two breakers?
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