Multiwire Branch Circuits

[daveselectric]

It is my understanding that when terminating a multiwire branch circuits [2 hots, phase a & b, shared neutral] on the same yoke [split tab] that the circuit breakers have a handle tie to shut off both circuits at the same time. Recently we installed a multiwire branch circuits in a 4" square using a raised cover and terminating each circuit on its own duplex receptacle. The inspector cinsidered this the same yoke and required a handle tie on the circuit breakers. What is the correct method according to the NEC?

 

[bphgravity]

Re: Multiwire Branch Circuits

I think this is a misinterpretation of what exactly a device yoke is and what the UL listing is of an "RS" type cover. It is my opinion that you indeed have two separate devices on two separate yokes, therefore not needing the tied breaker. However, from a design and safety standpoint, it is always a good idea to either label and document within the box that there are two supplies in the box, or tie the circuit breakers as requested by the inspector.

 

[electricmanscott]

Re: Multiwire Branch Circuits

Certainly this would be two seperate yokes. The inspector is wrong. Not a bad idea two have a two pole breaker I guess. But any good electrician would recognize this as a multiwire circuit and would know how to handle it.

 

[charlie]

Re: Multiwire Branch Circuits

I agree with both bphgravity and electricmanscott in their interpretations. However, keep in mind that the Code is a book of minimums. The inspector is correct in his concern, especially for a dwelling where Joe Homeowner will get into it but an inspector can not write and enforce his own Code.

 

[tom baker]

Re: Multiwire Branch Circuits

Only devices on the same yoke require a two pole circuit breaker. Do you have Mike Holts 2002 Illustrated Changes to the NEC? It has a great graphic of this.
However, depending on the location two recptacles in the same outlet on different circuits could present a hazard, if an less experienced person was to work on it with out testing voltage.

 

[electricmanscott]

Re: Multiwire Branch Circuits

Here we go with the "What if the homeowner....." :roll: That is their problem. If you want to play with fire you must consider that you may get burnt. I follow the NEC and loose no sleep over what ifs. Notice there is no definition for "Idiot Proof" in the code book.

 

[jxofaltrds]

Re: Multiwire Branch Circuits

Dave

You are correct.

Ask him what he would do if he had a four gang with different circuits in it.

Where in O H I O ?

Mike P.

[ March 05, 2003, 06:37 PM: Message edited by: jxofaltrds ]