Min Service Disc. Size - Emergency feeder

[Designer69]

Last question on this I promise.

My emergency branch only has 1KVA of load on it (em. lights) and all I would really need is a 15 or 20A Service Disconnect for it.

However am I required to use 230.79(D) here and have a minimum 60A breaker? (the em. branch is a panel with 4 breakers and 230.79 A-C don't apply)

 

[lielec11]

Why not replace the 400A switch with a 400A panel and feed the EM circuits through a separate ATS from the panel? That way you still maintain your ATS separation and can use a 20A branch circuit like you want to?

 

[Gshell82]

hmmm I don't think that would work

 

[lielec11]

Why wouldn't that work? Unless there are some other restrictions I'm unaware of?

 

[steve66]

Why wouldn't that work? Unless there are some other restrictions I'm unaware of?

I agree, that should work. I don't know why you would run a separate service lateral just for the emergency lights. I think a separate service lateral or service is only required for a fire pump.

 

[Designer69]

Why wouldn't that work? Unless there are some other restrictions I'm unaware of?

I need the entire building on the generator (400A ATS). That panel would only be there to split the feed to the 2 ATS and no other purpose.

Seems like a lot extra just to be able to have a 20A emerg. breaker for the second ATS.

 

[Designer69]

Unless I do it like this? Is that better?

 

[lielec11]

Unless I do it like this? Is that better?

View attachment 20793

You would need an OCPD between the trough and the ATS on the left to meet 240.21, unless the ATS had a CB or fuse built into it

 

[Designer69]

It should be acceptable as is right? Wouldn't the 20A feed now just become a feeder tap after the now 400A Service Disconnect.

I think I had this exact configuration on this post and Kwired said it's acceptable;
http://forums.mikeholt.com/showthread.php?t=192553&page=3