Multiwire Branch Circuit

[czarstoo]

This seems like an easy question, so I hope there is an easy answer. Are the circuits that are used to typically provide 240 V power to residential ranges, hot water heaters, dryers, pool pumps, etc considered to be multiwire branch circuits? The NEC definition of MWBC seems to indicate the answer is yes!

 

[iwire]

Re: Multiwire Branch Circuit

Only if you bring an grounded (neutral) conductor along with the ungrounded conductors.

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.

 

[czarstoo]

Re: Multiwire Branch Circuit

Understand! Therefore, circuits to ranges and dryers that require and insulated neutral are MWBC and 240 V hot water heaters and pool pumps that do not require a neutral are not MWBC. correct??

 

[charlie b]

Re: Multiwire Branch Circuit

Correct.

 

[czarstoo]

Re: Multiwire Branch Circuit

OK! Now, what do you call the circuits that provide power to older ranges and dryers that utilize the 3 conductor connections where the neutral and ground currents both flow on the uninsulated conductor?

 

[roger]

Re: Multiwire Branch Circuit

It's still a MWBC without a seperate EGC.

Roger

 

[mc5w]

Re: Multiwire Branch Circuit

However, a 3-wire 3-phase branch circuit that uses 3 hot wires and no neutral is somehow NOT a multiwire branch circuit of at least the definitions for 2-wire and multiwire branch circuits do not include 3 wire 3 phase branches.

 

[George Stolz]

Re: Multiwire Branch Circuit

Originally posted by mc5w:
However, a 3-wire 3-phase branch circuit that uses 3 hot wires and no neutral is somehow NOT a multiwire branch circuit of at least the definitions for 2-wire and multiwire branch circuits do not include 3 wire 3 phase branches.

Yes, it does.

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.

 

[roger]

Re: Multiwire Branch Circuit

George, a MWBC has to have a grounded conductor (neutral) as part of the circuit.

Note the wording "and a grounded conductor".

I'm still not sure of what mc5w actually said in that post though.

Roger

 

[George Stolz]

Re: Multiwire Branch Circuit

Ooooohhh. I goofed. I need to slow down, enjoy the flowers.

 

[infinity]

Re: Multiwire Branch Circuit

Would a 3 phase branch circuit from a 3 wire delta system be a MWBC by definition?

 

[ryan_618]

Re: Multiwire Branch Circuit

Originally posted by infinity:
Would a 3 phase branch circuit from a 3 wire delta system be a MWBC by definition?

No.

Edit: Well, the more I think about it, I guess it could be

[ May 12, 2005, 09:12 AM: Message edited by: ryan_618 ]

 

[infinity]

Re: Multiwire Branch Circuit

Sorry I left out a corner grounded 3 wire delta.