Does a MWBC Count as 1 or 2 Added Circuits on Permit?

Tom PultzJanuary 6, 2010

As I work my way through all the wiring changes I'm doing I've decided to add several shared neutral multi-wire branch circuits (MWBCs), e.g., replace old 12/2 and 14/2 dishwasher and disposal circuits with one 12/3 MWBC.

The online permitting process just asks how many circuits are being added or changed and asks for a description of same... so does a MWBC count as 1 or 2 new circuits? I can see it being counted as 2 circuits since electrically they are on seperate hot busses... but since I'm only stringing one set of main 12/3 wires that will be hooked to the same 2-pole breaker with one neutral and one ground I don't really see why I should pay double the price for one additional wire.

Can anyone clarify what the standard practice is for MWBCs and permits? Thanks.

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I think this would be a local interpretation issue. In the eyes of the NEC it is BOTH one and two circuits depending on how you apply it.

I don't think you can argue that it is two circuits as far as branch circuits go, but if it is feeding a detached structure it can and is considered one circuit.

    Bookmark   January 6, 2010 at 8:03PM
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Ron Natalie

It's a local interpretation thing (the NEC doesn't say squat about permit charges).
Here it's two circuits as far as the billing on the permit goes.

    Bookmark   January 6, 2010 at 10:23PM
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It is a local issue with the permit department.

A number of places I work count every breaker pole as a separate circuit, making every 240 V load two circuits for permit purposes.

A multi-wire is the same, two breakers, two circuits for the permit.

It is a revenue thing, not an NEC thing.

    Bookmark   January 7, 2010 at 9:50AM
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Tom Pultz

Thanks for the input. I sent an email to the local Labor & Industries office that handles electrical inspections, etc. and asked the question.

The response was: a MWBC counts as two circuits and a 240V circuit counts as one. This is how I originally specified the circuits to be added or modified on the permit, so it should be OK.

    Bookmark   January 9, 2010 at 2:43PM
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