Art 255 Single Circuit

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augie47

augie47

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Help me with a bit of confusion here.
225.30 states a multi-wire branch circuit is considered a single branch circuit for the purpose of that section.
Then in 225.39(B) it states an installation of not more than two 2 wire branch circuits shall have a rating of not less than 30 amps.
and 225.39(A) states a single branch circuit can be not less than 15.

The way I read this, I can have one 15 amp (or 20) multiwire branch circuit feeding a outbuilding with say lighting on circuit A and receptacles on circuit B and use a switch as disconnecting means.

The 30 amp minimum would apply if I had two overcurrent devices in the outbuilding. (an example would be feeding a 240v well & a light)

I'm confused in that in scenerio "A" I do have two-2 wire branch circuits
so 225.30(B) leads me toward a 30 amp mininum, but 225.30 states that is considered one branch circuit.
 
augie47 said:
the 30 amp minimum would apply if I had two overcurrent devices in the outbuilding. (an example would be feeding a 240v well & a light)

I'm confused in that in scenerio "A" I do have two-2 wire branch circuits
so 225.30(B) leads me toward a 30 amp mininum, but 225.30 states that is considered one branch circuit.
Click to expand...

Gus this is where you lost me. If you have one MWBC it's considered one circuit for the purposes of 225.30. Is that what you have or do you have 2- two wire circuits?
 
infinity said:
Gus this is where you lost me. If you have one MWBC it's considered one circuit for the purposes of 225.30. Is that what you have or do you have 2- two wire circuits?
Click to expand...

Rob, I guess thats the key to my confusion. I have ONE multi-wire branch circuit feeding the outbuilding which then supplies two-2 wire circuits..one a light, one a receptacle. so :D I have both, one multiwire per 225.30, which becomes two-2 wire per 225.39
 
augie47 said:
Rob, I guess thats the key to my confusion. I have ONE multi-wire branch circuit feeding the outbuilding which then supplies two-2 wire circuits..one a light, one a receptacle. so :D I have both, one multiwire per 225.30, which becomes two-2 wire per 225.39
Click to expand...

I agree with walker. It is still a mwbc.
 
Let me stick my neck out a little further. The building is fed with only one mwbc. Once it hits the discos they are no more than the load sides of the MWBC.
 
1. read the definition of branch circuit, multiwire. Remember that this definition by it's placement in Art 100 makes it applicable throughout the NEC unless otherwise modified or supplemented.

2. Art 225 states that separate structures/buildings are only permitted to be SUPPLIED by one branch circuit or feeder.

There is permission to use the multiwire branch circuit as one branch circuit, even though the definition already has it qualified as one branch circuit.


Augie
In your case, the building is supplied with one branch circuit. How one wires the interior of that building has no effect in regards to the supply.

The use of one branch circuit also gives relief as to the grounding electrode system requirements. ;):cool:
 
augie47 said:
The 30 amp minimum would apply if I had two overcurrent devices in the outbuilding. (an example would be feeding a 240v well & a light)
Click to expand...

Any overcurrent devices in the outbuilding (load side of disconnect) have no bearing on the matter. All that matters is the outbuilding's FEEDER be a MWBC up to and through the disconnect. What happens after the disconnect is of no concern in this regard.
 
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