Building Disconnect Location

[nhee2]

Is there a maximum distance (explicitly stated or generally accepted) between a building disconnect and building? For instance - install a Circuit breaker at the secondary of a customer owned transformer (unit substation). Secondary feeder supplies the building. The building is the only load, and there are no alternate supplies to the building. The unit sub is roughly 20' from the building. Can the circuit breaker be my disconnect, feeding a MLO switchboard within the building? Application is 480V 3ph 3000A. I am not even certain I can get a MLO switchboard but assuming I can, would I need a separate disconnect anyway?

 

[augie47]

Take a look at 225.32, especially Exception1 and see if that is applicable.

 

[nhee2]

Thanks augie. Possibly. The customer does not have in-house electrical staff, so I am not convinced we would meet the intent of 'monitored by qualified individuals'. So I was trying to determine how much latitude is generally applied in 'nearest the point of entrance of the conductors'. 0 ft? 5 ft? 15 ft?

 

[augie47]

The distance would, IMO, be an AHJ call. The problem I see is, barring the exception, 225.32 does not seem to lend itself to the disconnect being located remote from the building (one could play a word game).
To add controversy, if you are under '11 or '14, 225.36 requires the disconnect to be SUSE. Would a feeder breaker in a panel be judged as SUSE ???

Sticky situation....

 

[nhee2]

I read that 225.36 requires SUSE when I am using the grounded conductor as the fault return path. If an EGC is run and the grounded conductor is isolated from the EGC/GEC, then I did not think SUSE would be required. Although in my proposed installation the CB would be the secondary main off of the unit substation transformer and would / could likely be SUSE.

However your overall point of reviewing with AHJ is probably the best approach.

 

[augie47]

(just for the record, I don't see what you see in 225.36 but that section has changed in some Code cycles, so your viewpoint may be valid).
Back to your OP, I don't think you would have a problem finding an MLO switchboard and apply the six disconenct rule.

 

[nhee2]

Augie,
Thanks for the help. My thoughts on 225.36 were based on the requirement for SUSE applying only when using 250.32(B), exceptions. 250.32(B) exceptions are related to installations where the grounded conductor is used as the fault path. I am looking at 2014 code. Although I could be looking at it incorrectly...

 

[jumper]

I read that 225.36 requires SUSE when I am using the grounded conductor as the fault return path. If an EGC is run and the grounded conductor is isolated from the EGC/GEC, then I did not think SUSE would be required.

:?:?:?

225.36 Suitable for Service Equipment. The disconnecting
means specified in 225.31 shall be suitable for use as
service equipment.

225.31 Disconnecting Means. Means shall be provided
for disconnecting all ungrounded conductors that supply or
pass through the building or structure.

 

[nhee2]

I assume that is 2011? I don't have the pdf version. My 2014 handbook -

225.36 Type:
The disconnecting means specified in 225.31 shall be comprised of a circuit breaker, molded case switch, general-use switch, snap switch, or other approved means. Where applied in accordance with 250.32(B), Exception, the disconnecting means shall be suitable for use as service equipment.