225.33(B)

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charlie b

charlie b

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A small building, remote from the main building, needs 120 volt power for receptacles and for lights. I reviewed the design and noted that it called for two separate circuits to be run from a panel in the main building. It also had two separate disconnect switches on the outside of the small building. I pointed out to the designer that 225.30 would not allow two branch circuits, and that a MWBC would be needed. I know that we will need to do something with the building's required disconnecting means. I see that 225.33(B) allows two separate single pole disconnects to serve this function. But how do we handle the shared neutral? Here is what I am thinking:
  • From a two-pole breaker on the branch panel, run one conduit to the first disconnect, with both ungrounded conductors, the shared neutral, and the shared EGC.
  • Tap the neutral, and run it, along with the ungrounded conductor on the load side of the disconnect, to the receptacle loads.
  • Run the other ungrounded conductor, along with the tapped neutral, to the other disconnect switch, to serve the lighting loads.
  • Provide a listed handle tie between the two disconnect handles.
Does this make sense? Am I over thinking this?
 
Do you need GFCI at that bldg and is the MWBC going to be a problem with that?
 
mgookin said:
Do you need GFCI at that bldg and is the MWBC going to be a problem with that?
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I don't think so. This will be a storage area for large O2 tanks. It will have three walls, a roof, and a fence/gate for access. I would not call that "outdoors."

 
charlie b said:
Do they make such things as "suitable for use as service equipment," as is required by 225.36?
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A snap switch doesnt need to be SUSE rated.See 225.36 Exception in the 2011NEC. In the 2014 NEC it only needs to be SUSE rated when the supply to the building is installed in accordance with the Exception to 250.32(B).
 
charlie b said:
A small building, remote from the main building, needs 120 volt power for receptacles and for lights. I reviewed the design and noted that it called for two separate circuits to be run from a panel in the main building. It also had two separate disconnect switches on the outside of the small building. I pointed out to the designer that 225.30 would not allow two branch circuits, and that a MWBC would be needed. I know that we will need to do something with the building's required disconnecting means. I see that 225.33(B) allows two separate single pole disconnects to serve this function. But how do we handle the shared neutral? Here is what I am thinking:
  • From a two-pole breaker on the branch panel, run one conduit to the first disconnect, with both ungrounded conductors, the shared neutral, and the shared EGC.
  • Tap the neutral, and run it, along with the ungrounded conductor on the load side of the disconnect, to the receptacle loads.
  • Run the other ungrounded conductor, along with the tapped neutral, to the other disconnect switch, to serve the lighting loads.
  • Provide a listed handle tie between the two disconnect handles.
Does this make sense? Am I over thinking this?
Click to expand...

I'd come from a 2p breaker in the main panel and pull a small feeder to a 4 or 6 circuit MLO panel In the out building and put in (2) 1p breakers out there.
You'd never regret it.

JAP>
 
jap said:
I'd come from a 2p breaker in the main panel and pull a small feeder to a 4 or 6 circuit MLO panel In the out building and put in (2) 1p breakers out there.
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That would have been my preference too. But this is not my project, not my circus, not my monkeys.
 
charlie b said:
That would have been my preference too. But this is not my project, not my circus, not my monkeys.
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JMHO but pulling (2) separate circuits to an out building for this is a bad design.
It leaves no room for an added circuit in the future and by the time you do all what was talked about above to try and make things work the subpanel at the outbuilding regardless of how small would be a much better circus and a cuter monkey.

JAP>
 
charlie b said:
A small building, remote from the main building, needs 120 volt power for receptacles and for lights. I reviewed the design and noted that it called for two separate circuits to be run from a panel in the main building. It also had two separate disconnect switches on the outside of the small building. I pointed out to the designer that 225.30 would not allow two branch circuits, and that a MWBC would be needed. I know that we will need to do something with the building's required disconnecting means. I see that 225.33(B) allows two separate single pole disconnects to serve this function. But how do we handle the shared neutral? Here is what I am thinking:
  • From a two-pole breaker on the branch panel, run one conduit to the first disconnect, with both ungrounded conductors, the shared neutral, and the shared EGC.
  • Tap the neutral, and run it, along with the ungrounded conductor on the load side of the disconnect, to the receptacle loads.
  • Run the other ungrounded conductor, along with the tapped neutral, to the other disconnect switch, to serve the lighting loads.
  • Provide a listed handle tie between the two disconnect handles.
Does this make sense? Am I over thinking this?
Click to expand...


This makes total sense.. I would use a dp snap switch at the building and you are good to go. The 2014 allows something like an a/c disconnect but older versions don't specifically allow it...
 
Dennis Alwon said:
This makes total sense.. I would use a dp snap switch at the building and you are good to go. The 2014 allows something like an a/c disconnect but older versions don't specifically allow it...
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To me it never has made sense to feed (2) individual 120v circuits from a 2p breaker and never will.

JAP>
 
charlie b said:
Do they make such things as "suitable for use as service equipment," as is required by 225.36?
Click to expand...

SUSE means it has the means to bond the neutral and can be used for a feeder panel.
SUSE ONLY means the neutral is bonded and this panel can't be used for a feeder panel
 
jap said:
I'd come from a 2p breaker in the main panel and pull a small feeder to a 4 or 6 circuit MLO panel In the out building and put in (2) 1p breakers out there.
You'd never regret it.

JAP>
Click to expand...
That would trigger a requirement for a grounding electrode system at the second building, where a single multiwire circuit does not require a grounding electrode system.
 
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