Emergency Generator Question-ATS

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faresos

Senior Member
Hello every one.....

I have a question regarding the emergency power; Can we put the entire building (parking garage) on emergency power generator with one automatic Transfer Switch or I need to provide another ATS for life safety loads such as emergency lighting?

Thanks,
Sam
 

DARUSA

Senior Member
Location
New York City
I think not!!!
You can use one generator for all you loads but the loads need to be separate, Emergency Load from other Loads that means you will need two separate TS.
 
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DARUSA

Senior Member
Location
New York City
700.6 D-Use. Transfer equipment shall supply only emergency loads.

Although the alternate power source is permitted to supply emergency loads as well as other
loads, the transfer switch used for the emergency system is strictly limited to emergency loads,
that is, loads classified as emergency in accordance with 700.1. Other loads, such as legally
required standby loads or optional standby loads (covered by Articles 701 and 702), are not
permitted to be supplied from the emergency system transfer switch. Where a single generator
is used to supply both emergency and nonemergency loads, multiple transfer switches are
required.
 
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iwire

Moderator
Staff member
Location
Massachusetts
If the idea is to supply required egress lighting and optional loads with one generator you cannot do it with one ATS.

You can use one generador all loads but the loads need to be separate Emergency Load from other Loads that means you will need two separate TS.

Exactly, one generator can supply the entire building but you will need at least two transfer switches, maybe more.

All the the required emergency loads have to be kept on separate transfer switches, panels, raceways etc.

You also cannot just decide to call as many lights as you want 'emergency' only the legally required lighting can be connected to the emergency distribution system.


On the other hand, if the building does not require a a generator and it is just a voluntary installation it can be done under the rules of Article 702 and with just one transfer switch.


See 700.9(B)
 

iwire

Moderator
Staff member
Location
Massachusetts
So why can't the whole complex including parking be legally required and classed as emergancy?

Because the whole complex will not meet the requirements of 700.1 ..... unless the AHJ says it does which they should not unless the building is very odd.


I. General
700.1 Scope. The provisions of this article apply to the
electrical safety of the installation, operation, and maintenance
of emergency systems consisting of circuits and
equipment intended to supply, distribute, and control electricity
for illumination, power, or both, to required facilities
when the normal electrical supply or system is interrupted.

Emergency systems are those systems legally required
and classed as emergency by municipal, state, federal, or
other codes, or by any governmental agency having jurisdiction.

These systems are intended to automatically supply
illumination, power, or both, to designated areas and equipment
in the event of failure of the normal supply or in the
event of accident to elements of a system intended to supply,
distribute, and control power and illumination essential
for safety to human life.

The goal here is too prevent a short circuit on someones coffee maker circuit from tripping a breaker supplying required egress lighting or other 'true' emergency loads.
 

tkb

Senior Member
Location
MA
The problem is when you use the word "Emergency" a lot of things change.
I like the term "stand by".
 
Hello every one.....

I have a question regarding the emergency power; Can we put the entire building (parking garage) on emergency power generator with one automatic Transfer Switch or I need to provide another ATS for life safety loads such as emergency lighting?

Thanks,
Sam

The main goal of an emergency system is to be reliable. Hence the requirement to be a stand-alone system and not inter-wired with other, non-emergency circuits. (The larger your system of parallel and series connected components, the less reliable it is, given all other things being equal.)

The NEC goes as far to require the emergency system to be supplied by a dedicated ATS, but I would go further - from the design and reliability standpoint - and install a dedicated generator for it.
 

tryinghard

Senior Member
Location
California
Because the whole complex will not meet the requirements of 700.1 ..... unless the AHJ says it does which they should not unless the building is very odd.

The goal here is too prevent a short circuit on someones coffee maker circuit from tripping a breaker supplying required egress lighting or other 'true' emergency loads.
I agree and understand but the fact remains the whole building can be classified, and the municipal I've been working for has done just this.
 

iwire

Moderator
Staff member
Location
Massachusetts
I agree and understand but the fact remains the whole building can be classified, and the municipal I've been working for has done just this.

Which is both unusual and ill advised.

That really means there is no "Emergency System" there is only an optional standby system and they have lost the redundancy of an emergency system.
 

tryinghard

Senior Member
Location
California
Which is both unusual and ill advised.
That really means there is no "Emergency System" there is only an optional standby system and they have lost the redundancy of an emergency system.
I fought the fight similar as you noted and even added that their applications don?t seem to be "essential for safety to human life" but two cases now supply the whole building as what they classify emergency. They know the definitions of 700, 701, & 702; if anything I think their cases should be 701 ?legally required standby systems?
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
I agree and understand but the fact remains the whole building can be classified, and the municipal I've been working for has done just this.

They can't say the entire building electrical load is required. You can't put furnaces or office equipment on the emergency system for example. See 700.3, just as an example.

Which is both unusual and ill advised.

That really means there is no "Emergency System" there is only an optional standby system and they have lost the redundancy of an emergency system.


I agree. The emergency system is supposed to be a separate system. Just because a municipality says its OK doesn't make it OK.
 

tryinghard

Senior Member
Location
California
They can't say the entire building electrical load is required. You can't put furnaces or office equipment on the emergency system for example. See 700.3, just as an example.




I agree. The emergency system is supposed to be a separate system. Just because a municipality says its OK doesn't make it OK.
Good point but again they are the municipal and they are saying the whole building.
 

skeshesh

Senior Member
Location
Los Angeles, Ca
I agree with pretty much all the comments. I'm really quite surprised that they whole building can be classified as such, it absolutely defeats the purpose of having an emergency system. Can you provide some details about the building and its function?
 

tryinghard

Senior Member
Location
California
I agree with pretty much all the comments. I'm really quite surprised that they whole building can be classified as such, it absolutely defeats the purpose of having an emergency system. Can you provide some details about the building and its function?
One is an administration building the other is a compound that includes a sewer lift, fire station, and a few other buildings. Both cases include one ATS each.
 

tryinghard

Senior Member
Location
California
What makes you think it is an 'emergency' system and not 'optional standby'?
Actully it's what this municipal is calling them they own these locations, like I said earlier I think they are misusing terminology its not emergency might be legally required 701.
 
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