Can two buildings share a service disconnect?

[cppoly]

Can two buildings share the same service disconnect if it's outside?

I couldn't find a section in the code that says each building requires it's own service disconnect.

 

[LarryFine]

Can two buildings share the same service disconnect if it's outside?

I would say yes, but the second might still need its own.

 

[Little Bill]

I would say yes, but the second might still need its own.

How would you get around the requirement for a disconnect to be nearest point of entry?
I guess if each building's panel was a main breaker, that might work.

 

[LarryFine]

How would you get around the requirement for a disconnect to be nearest point of entry?

My response presumed said disconnect would be on, and qualify as the disco for the first building.

 

[cppoly]

Thanks.

Let's say it's a 400A/400A/3P service disconnect outside that is feeding two buildings. Are you allowed to feed one building with a set of 3/0 and the other building with another set of 3/0 leaving the terminals of this single disconnect? This is more of an OCPD question.

 

[LarryFine]

Let's say it's a 400A/400A/3P service disconnect outside that is feeding two buildings. Are you allowed to feed one building with a set of 3/0 and the other building with another set of 3/0 leaving the terminals of this single disconnect? This is more of an OCPD question.

Then you're under tap rules; unlimited outside, if I'm not mistaken.

Wait. 400a/400a? Is that a dual disconnect?

 

[cppoly]

Then you're under tap rules; unlimited outside, if I'm not mistaken.

Wait. 400a/400a? Is that a dual disconnect?

It's a regular 400A disconnect fused at 400A. Would that be tap rules in my example?

 

[LarryFine]

It's a regular 400A disconnect fused at 400A. Would that be tap rules in my example?

Yes. 400a OCP for conductors rated for less.

 

[tortuga]

I couldn't find a section in the code that says each building requires it's own service disconnect.

For separate buildings on a common property like a campus, where the service point is ahead of the buildings your looking for 225.31 or if it is service conductors 230.70

 

[cppoly]

Here's a diagram. Are the feeders considered protected by the 400A OCPD even though they're going into separate buildings?

 

[tortuga]

Here's a diagram. Are the feeders considered protected by the 400A OCPD even though they're going into separate buildings?

Those are outside feeders so your in article 225 and the requirement is 225.31
If you look at 225.32 generally each building is required to have a disconnecting means at a readily accessible location nearest the point of entrance of the conductors.
There is some relief under the exceptions which you should probably discuss with your AHJ before using, I have had mixed results with Exception 1.

 

[cppoly]

Those are outside feeders so your in article 225 and the requirement is 225.31
If you look at 225.32 generally each building is required to have a disconnecting means at a readily accessible location nearest the point of entrance of the conductors.
There is some relief under the exceptions which you should probably discuss with your AHJ before using, I have had mixed results with Exception 1.

Thanks wouldn't 225.31 be satisfied here since the single disconnect would be disconnecting all ungrounded conductors ?

 

[tortuga]

Thanks wouldn't 225.31 be satisfied here since the single disconnect would be disconnecting all ungrounded conductors ?

225.31 requires a disconnect be located 'nearest the point of entrance of the conductors' to each building or structure, so I'd say based on your diagram the disconnect shown does not meet 225.31 for either building.
To see if your design complies with the code we need more info on what the outdoor feeder conductors land on when they enter the buildings 1 and 2.

 

[PaulEd]

Does your service disconnect have double lugs on the load side to accomodate two sets of wires?
Your load size conductors are now feeders on the load side of the Service Disconnect switch. If 400amp fuses are servicing both sets the conductors are not sized at their ampacity.
Should have a disconnect switch at the separate structure unless you're allowed to use the Single Management exception.

 

[jaggedben]

The answer to the question in post #1 is simply: Yes.

The diagram in post #10 seems fine as far as what it shows, but disconnects with overcurrent protection would be required at each building to comply with the sections tortuga mentioned. (And other details not shown could further affect compliance.)

 

[PaulEd]

The answer to the question in post #1 is simply: Yes.

The diagram in post #10 seems fine as far as what it shows, but disconnects with overcurrent protection would be required at each building to comply with the sections tortuga mentioned. (And other details not shown could further affect compliance.)

It's permissible to parallel a set of 3/0 off a set of 400amp fused disconnect and run them to two separate buildings brining 200amps to each?

 

[jaggedben]

It's permissible to parallel a set of 3/0 off a set of 400amp fused disconnect and run them to two separate buildings brining 200amps to each?

Yes. Outside tap rule. You need them each to land on 200A OCPDs, that's the main thing.

 

[jaggedben]

240.21(B)(5)

 

[PaulEd]

Yes. Outside tap rule. You need them each to land on 200A OCPDs, that's the main thing.

Oh ok. The diagram didn’t show that.

 

[wwhitney]

On the general question as posed in the OP, 2023 NEC 230.70(A)(1) says that for a building supplied by a service, "The service disconnecting means shall be installed at a readily accessible location either outside of a building or structure or inside nearest the point of entrance of the service conductors." This phrasing applies the "nearest the point of entrance" requirement only when the disconnecting means is inside.

In contrast, 2023 NEC 225.31(B) says that for a building supplied by a feeder the disconnecting means "shall be installed either inside or outside of the building" and "the disconnecting means shall be at a readily accessible location nearest the point of entrance of the conductors." The "nearest the point of entrance" requirement applies even to an outside disconnect. Apparently you can't put your disconnect on the outside of the building and then run the feeder conductors 100 ft along the outside of the building before they enter the building.

So if you put your service disconnect on a post 3 ft away from the building, does that satisfy 230.70(A)(1)? Seems like it does. Then if you have 2 buildings 6 feet apart, with a single service disconnect on a post that is 3 ft away from each building, does that satisfy 230.70(A)(1) for each building? Seems like it does.

To make the last question interesting, let's assume the feeder conductors run from the single service OCPD to each building run to panels within each building that are far enough inside that they are not "nearest the point of entrance" of the conductors. Either because the feeder conductors are full sized (not a tap), or because using the 25' tap rule we can get far enough into the building.

Cheers, Wayne