Emergency Power

[budbla]

If a building is supplied emergency power (generator) at the service entrance via a SE rated automatic transfer switch can I eliminate the need for multiple ATS for the emergency, legally required and the optional standby systems?

I am looking for a Code reference for this type of setup.

 

[goindowner]

700.6 D says transfer equipment can only supply emergency loads.

 

[budbla]

Emergency Generator

Emergency Generator

I am aware of the requirements of 700.6(D). What I am asking is could the generator on the supply side of the service be interpeted as a seperate service under 700.12(D).

 

[pete m.]

IMHO, I don't think it could.

From Article 100:
Service. The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.

Pete

 

[iwire]

I am aware of the requirements of 700.6(D). What I am asking is could the generator on the supply side of the service be interpeted as a seperate service under 700.12(D).

First a 'service' can only come from a utility, check Article 100.

Second any genertor that supplies an entire building through a single transfer switch can not be an 'emergency' generator. It would have to be an optinal stand by generator and could not supply true emergency loads.

 

[charlie b]

Second any genertor that supplies an entire building through a single transfer switch can not be an 'emergency' generator.

Agreed. You would need separate transfer switches for emergency, for legally required standby, and for optional standby. But you can have a single generator supply power to all three of these ATS's.

 

[iwire]

But you can have a single generator supply power to all three of these ATS's.

I agree assuming that generator was purchesed with more then one output breaker. :smile:

 

[qcroanoke]

Agreed. You would need separate transfer switches for emergency, for legally required standby, and for optional standby. But you can have a single generator supply power to all three of these ATS's.

Charlie,
I'm curious as to which ATS would be required to send the start signal
to the generator.

 

[iwire]

I'm curious as to which ATS would be required to send the start signal
to the generator.

Thats an interesting question, you could rig them in parallel so they all send a start signal. It seems the code is silent on that issue.

 

[steve66]

I think parallel start circuit wiring is the norm.

Hey, I think I found something new we can debate: Does the code require the start wiring to be separate back to the generator??

Steve

 

[charlie b]

Hey, I think I found something new we can debate: Does the code require the start wiring to be separate back to the generator??

No, because the start wiring does not start the generator (i.e., it is the diesel engine, or other prime mover, that starts the generator). :wink:

 

[iwire]

Hey, I think I found something new we can debate: Does the code require the start wiring to be separate back to the generator??

IMO with a optional standby or a legally required unit they can be compliantly run together. With an emergency unit I am not sure, are the start conductors 'emergency conductors'?


FWIW many of the manufacturers instructions say to run them independently.

 

[charlie b]

. . . are the start conductors 'emergency conductors'?

"Emergency conductors" is not the relevant phrase. 700.9(B) speaks of separating wiring that comes from an emergency source and that supplies emergency loads from all other wiring. "Start wiring" is not part of the current path that supplies any emergency loads. So as long as you don't run any start wiring with any wiring to an emergency load, the code says you are OK.

 

[iwire]

700.9(B) speaks of separating wiring that comes from an emergency source and that supplies emergency loads from all other wiring. .

Sounds good to me. :smile: