How many ATS needed for the fire station?

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dahualin

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I am doing a fire station project. The entire fire station will be backed up by a generator. I thought only one ATS is needed after main breaker for the service and main breaker for the generator. I checked 700.6 of 2005 NEC handbook that says "If a single generator is used to supply both emergency and nonemergency loads, then multiple transfer switches are required" . So I have to use at least two ATS, one for emergency load such as emergency lights, the other for nonemergency load such as HVAC units. And I have to put four more disconnects for protecting the two ATS. Do I have to do it this way?

Any ideas will be appreciated.

David
 
ryan_618 said:
If the generator picks up emergency loads, such as emergency lighting and exit signage, you need two.
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I agree with Ryan and will add that these two ATSs will need to be supplied from separate breakers on the generator.

You can order the generator with more than one output breaker.
 
Not so fast!

dahualin said:
The entire fire station will be backed up by a generator.
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Why? Too many people mis-use the word "emergency." Are these "emergency lights" really what the NEC calls "legally required and classified as emergency by municipal, state, federal, or other codes" (Article 700)? Or are they "legally required standby" (Article 701)? Or are they "optional standby" (article 702)?

If these are "emergency lights," if for example the egress lights are not battery backups but are supplied by the generator, then (as Ryan and Bob have said) the ATS that supplies them cannot supply non-emergency loads.
dahualin said:
And I have to put four more disconnects for protecting the two ATS.
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A disconnect does not provide protection. What makes you think you would need "four more"?
 
The main breaker for service and the main breaker for generator are rated 800 amps. The two ATS will be rated 100 amps and 600 amps respectively. So I need put two 100 amps breakers (0ne for normal power, one for generator power) for 100 amps ATS; two 700 amps breakers (one for normal power, one for generator power) for 600 amps ATS. That will take a lot of our limited space.
 
dahualin said:
That will take a lot of our limited space.
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In my area the emergency distribution equipment has to be in a separate fire rated room.

Yes it takes up a lot of space.

Here is a possible suggestion.

Put in minimum required egress lighting utilizing some sort of battery units including the exits.

You now have a code compliant building.

Now install your Article 702 Optional standby generator and feed any optional loads you want. Some of those optional loads could include many lights and even the feeds to the previously mentioned EBUs and Exits.

When the power fails you have instant although dim lighting throughout.

When and if the generator starts you will have more lighting and the EBUs / Exits will be charging back up. To be ready if the generator fails.

IMO going this route avoids the costs of two ATSs and provides a good design with some redundancy.

JMO, Bob
 
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If you choose service entrace rated transfer switches, you may be able to eliminate the disconnects. Spec the generator with 100 amp and 600 amp main line circuit breakers. Feed the 100 amp and 600 amp service entrance rated transfer switches straight from the generator and poco xfmr. Downstream of the xfer switches, feed your "emergency" and "optional" standby equipment.

Here is an example of a service entrance rated xfer sw.
http://www.asco.com/cgi-bin/redirect.pl?/product.html
 
Was gonna start a new thread, but my question is about this threads' subject. If I design a building electrical system and include a generator to back-up the entire building, then so long as the building electrical design meets the requirements of life safety and so on without a generator(according to the local AHJ), then I can utilize a single service entrance transfer switch. Is this correct?
 
Gasguzzler:
:)

Thats right. For example, you could use battery packs and exit lights with batteries in them. Then all the "emergency system" wiring is internal to the fixtures.

You just have to be careful to make sure the battery pack lights will come on if power is lost. For example, you usually need to put the emergency lights on the same branch circuit as the normal lights. If you put them on a separate circuit, there is a chance the normal branch breaker will trip, but the emergency lights won't come on.

Steve
 
sceepe said:
If you choose service entrace rated transfer switches, you may be able to eliminate the disconnects. Spec the generator with 100 amp and 600 amp main line circuit breakers. Feed the 100 amp and 600 amp service entrance rated transfer switches straight from the generator and poco xfmr. Downstream of the xfer switches, feed your "emergency" and "optional" standby equipment.
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That would still leave a Article 700 violation if those service rated transfers supplied 'mixed' emergency and normal loads.
 
For what it's worth, I'm desiging two Police Facilities right now with 100% emergency backup. Both facilities want 72 hours of emergency power available!

When I asked why the excessive amount of hours on emergency, both clients stated that Hurricane Katrina changed their way of thinking. Call it the "Katrina Effect". As a result of this overkill, I have to supply belly tanks as well as supplemental aboveground fuel tanks as well.

However, I have found an excellent parallel Generator package manufactured by Generac that limits the amount of equipment and space required for projects such as these.
 
iwire said:
That would still leave a Article 700 violation if those service rated transfers supplied 'mixed' emergency and normal loads.
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If the 100 amp switch feeds only the emergency loads and the 600 amp switch feeds all the remaining loads whats the violation?
 
sceepe said:
If the 100 amp switch feeds only the emergency loads and the 600 amp switch feeds all the remaining loads whats the violation?
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I guess I am just not getting what you are proposing.

You suggestion still requires two ATS now Service rated.

You still will need a generator with two separate output breakers.

If anything I see your option as an increase in costs not a reduction.

BTW, I like that signature, it makes me laugh each time. :D DOH!
 
Be careful with those battery packs. In a hi-rise bldg you cannot use battery packs, you have to use a genset per the bldg code. Your bldg code may vary in your state.

How big is this fire station? the service for our typical station is probably 600 amps at 208V. It would probably never trip a 400amp c/b.

Remember the emergency requirement for lighting does not kick in until your occupant load is 100 or more. That's alot of firefighters. Our stations probably hit 50 max.
 
sandsnow said:
Remember the emergency requirement for lighting does not kick in until your occupant load is 100 or more. That's alot of firefighters. Our stations probably hit 50 max.
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That will depend upon what building code applies. Under the IBC the requirement would kick in at 50 occupants or 75 feet of maximum travel distance to an exit. If the building is two stories, the occupant load would only need to be 30. If any part of the building was classified as an R occupancy, the occupant load would only need to be 10.
 
IWIRE,

I was only talking about the original question which said "And I have to put four more disconnects for protecting the two ATS. Do I have to do it this way?"

With service entrace rated ats, he wouldn't need a bunch of disconnect switches. I never said it would be cheaper. My point was only that you could do it without the disconnect switched and still meet code. I think I'm correct. That is at least until Charlie comes back with some reference to some obscure article that I glossed over 10 times and shows me that everything I thought I knew is a bunch of poo.
 
eprice said:
That will depend upon what building code applies. Under the IBC the requirement would kick in at 50 occupants or 75 feet of maximum travel distance to an exit. If the building is two stories, the occupant load would only need to be 30. If any part of the building was classified as an R occupancy, the occupant load would only need to be 10.
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That is a eye opener. 30 people and you need emergency lighting. That will leave a mark when and if we ever go to the IBC.

So on an R occupancy, 10 people (right conditions) and you need emergency lighting??

I gotta get a preview of that. I think someone in the office has an IBC
 
sandsnow said:
That will leave a mark when and if we ever go to the IBC.
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You think thats bad, wait till you see the "special inspections" required in chapter 1 of the IBC. All concealled electrical work (mechanical and plumbing also) has to be inspected before it is coved up. For a 100,000 sqr ft commercial building, how many inspections will it take to see everythinyg under the slab, in the block walls, or above a hard ceiling?
 
We do that now. I look at stuff under the slab and behind any drywall or lath. The block walls we just look at the first lift or two to see how they are doing it.

By "special inspections" I assume you mean what we call a deputy inspector who would be employed by the owner. Currently these guys do stuff like concrete cylinders and fireproofing (monokote) inspection.
 
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