ECN Forum Forums Code Related Discussion NEC & other Code issues emergency generator 2 bldgs

i'm really weak on generators and emergency circuits..... ok, i'm weak on everything anyway, plans are showing an emergency generator serving two buildings [one existing with the e-gen. and one planned] on the same property, but it doesnt show a disconnect entering the new bldg or a transfer switch at the generator.. all it shows is a single emergency power circuit coming from the existing buildings generator.

is a transfer switch at the generator location the correct way to do this? 700.6

is it allowed to use a relay at the second building to signal the generator that the e-circuits are needed?

and i assume i would need to put phenolic labels at both buildings even if its only e-power? 225.37 for svc. 700.8 for gen.

225.31 says it needs a disconnect regardless of their being emergency circuits or normal? and to be s.u.s.e. 225.36

anything else?

Cindy,
Sorry, your question deserved an answer before this. You answered most of them though, and did raise a few more.

We assume here that the buildings are on the same circuit from the utility, if not, some answers change. IF they are, then only one transfer switch would be necessary, since if the utility fails, it would start.

If you are using this genset to replace emergency batteries (unit equipment) then yes, you should put a relay in the second building, and could put a second transfer switch in that would transfer ONLY that building. I would view that as optional, since generally the idea behind emergency equipment is to guard against utility failure, and that is covered with the one transfer switch. Realize that unless your doing this in No. Va. , I can't speak for your local AHJ.

Yup, I would say 700-6, 701-7, 702-6 all state that labeling at the service is required.

The relay at the second building (I assume you mean a start relay here) would signal the genset to take the em load of BOTH buildings, but yeah, there's nothing illegal about this, I just think it unneccessary. Again we are concerned about Utility failure, and we should have that covered with the K relays in the xfr switch.

445-10 says the disconnect may or may not be necessary (probably not) but I don't know exactly what type of equipment you have here. The transfer sw. is a disconnect, and you can (probably) shut the genset down.

Clear as mud????????? Good luck.

both buildings are on the same transformer with a transfer switch at the existing building generator, so i guess thats enough as long as its ok to connect both buildings e-circuits into the same transfer switch.
about 445-10, not too sure how readily it could be shut down, doesnt seem like too good of an idea to have to run through a parking lot and enter the generator area to shut it down. thanks