Disconnects when branch circuit supply other buildings

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11Haze29

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Electrical Engineer
Situation is this. Three buildings clustered together with interconnecting breezeway, called building A, B, and C. Building A has a utility transformer supply with disconnect at service entrance. Buildings B and C, each have a branch circuit feeder from Building A.

Question: Does building B and C require a local disconnect. their branch circuits do have OCPD and cable is per Art 310.

Haven't found anything in NEC that says Buildings B and C need a local disconnect, and don't see the feeders to these buildings as a 'Service'.

What do you thing??
'
 
You've called them both branch circuits and feeders; they can't be both.

What do the conductors land on at the load ends?

You may have to find out whether they're "legally" considered one or three structures.
 
FWIW. Unless there are fire doors involved, our Building guys would consider that as one building. Might be worth confirming.
 
norcal said:
Would the breezeways make the buildings attached or not?
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Here, they do for residential garages, as one example.

I believe the specific rule is either at least ten feet of separation or attached by at least a breezeway.

In other words, no two detached structures may be less than ten feet apart.
 
11Haze29 said:
Situation is this. Three buildings clustered together with interconnecting breezeway, called building A, B, and C. Building A has a utility transformer supply with disconnect at service entrance. Buildings B and C, each have a branch circuit feeder from Building A.

Question: Does building B and C require a local disconnect. their branch circuits do have OCPD and cable is per Art 310.

Haven't found anything in NEC that says Buildings B and C need a local disconnect, and don't see the feeders to these buildings as a 'Service'.

What do you thing??
'
Click to expand...

1. The connections to B and C are feeders, not branch circuits unless they only feed loads. It is either a feeder or a branch or a service. Understand the terms or you will not understand NEC. Each type has its own section. Do not mix.
2. Distribution in B and C are sub panels. They are fed from the MDP which has to have an OCPD to protect the feeder. The subpanel by definition doesn’t have or need a breaker. However, often a prepopulated stock panel is used and the main breaker is left in place as a disconnect. It’s not required but it is much easier to switch it off when working on something in building B or C without walking back and forth, and if the panel main is say 200 A and the feeder breaker is say 100 A, it shouldn’t ever need to trip except as backup if the feeder breaker fails.
3. In a large campus it’s not uncommon to see each building set up with a service and the distribution system in between is all services. This is particularly true with say pulp and paper or refineries where they have large cogens on site and OSHA requires them to fall under utility regulations. But since at that point you are out of NEC and into NESC, and acting as a private utility NEC doesn’t even apply.
 
They are feeders from A to B and C. They feed distribution panels in B and C. There are no firewalls or doors between the buildings.
 
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