100 Amp Panel tapped off of 400 Amp Disconnect?

[Stevareno]

I went on a service call today for a routine problem. In the process of troubleshooting, I noticed something I have not seen before.

Two separate buildings. The main building is fed with a 400 amp service.
The secondary building has a panel with a 100 amp main breaker, that is fed from the load side of the 400 amp disconnect on the main building. The conduit run is obviously over 100 feet with #3 copper.

This doesn't seem "legal" to me, yet it is a commercial installation (church) so I would think that it had been inspected by the city and approved.

Doesn't an installation like this fall under the 25' tap rule? At the very least, I think they should have put a fused 100 A disconnect for the secondary building next to the 400 A disconnect at the main building.

 

[augie47]

You might take a look at 240.21(B)(5) for outside taps. If it meets all the parameters it's legal install.
(250.32 would be applicable also)

 

[GoldDigger]

Doesn't an installation like this fall under the 25' tap rule? At the very least, I think they should have put a fused 100 A disconnect for the secondary building next to the 400 A disconnect at the main building.

Does the installation of the feed to the secondary building qualify under 240.21B(5)?

Typed too slow....

 

[cdslotz]

So the 400A main switch is on the exterior of bldg A, 100A tap to the load lugs, then underground to bldg B?
Or is it run on the exterior of wall to bldg B?

Not that it matters. Although I would not have done it that way, but as long as it's considered "outside of the bldg" and is fused upon entering bldg B, I think it's compliant.

I don't have a code book with me, you need to know if it meets the definition of "outside the bldg"

 

[Stevareno]

So the 400A main switch is on the exterior of bldg A, 100A tap to the load lugs, then underground to bldg B?

Correct. It goes from the main switch at bldg A, underground all the way to the panel inside bldg B.

 

[kwired]

Many may put a disconnect or breaker on this so that you wouldn't have to shut off the 400 amp switch to kill the 100 amp feed, but otherwise it sounds acceptable.