Automatic Transfer Switch Location Requirements

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mjaenke

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On a recent hotel Job, my electrical drawings were disapproved saying that the Automatic Transfer Switch needed double the clearance in the electrical room. Up until now i assumed that the transfer switch needed 3.5' in front to comply with NEC art. 110.26. If i'm reading art. 2002 NFPA 110 7.2.2 and 7.2.2.1 correctly, the transfer switch was allowed to be installed in the main electrical room IF double the distance was provided. The 2005 NFPA took out this exception. I cannot find any article in the NEC that talks about where to mount or clearances for transfer switches. Going with the information i have, am i forced to assume that transfer switches cannot be located in the same room as other service equipment? Why???

Thanks,

Matt Jaenke
 
Here in MA emergency distribution equipment must be 'fire separated' from normal distribution equipment.

It would not surprise me if other areas have similar rules or that the NFPA is heading that way.
 
iwire said:
Here in MA emergency distribution equipment must be 'fire separated' from normal distribution equipment.

It would not surprise me if other areas have similar rules or that the NFPA is heading that way.
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I agree and should be.
 
iwire said:
Here in MA emergency distribution equipment must be 'fire separated' from normal distribution equipment.
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This triggers a vague memory of a project-related debate from a year or so ago. I don?t have time to pin it down right now, but here is the gist of the discussion. Somewhere in the non-NEC-related NFPA documents (NFPA 101 or 110, perhaps), there are rules about keeping ?Emergency Power Supply System? (EPSS ? or at least I think that was the term they used) equipment in separate locations from normal supply equipment. But the definitions of ?emergency? and ?normal,? as used in that other NFPA document, were not the same as the definitions used in the NEC. What I recall is that the EPSS was the diesel engine, the attached generator, and the related components (e.g., fuel pumps, oil pumps, etc.). The ATS, the emergency switchboard, and other emergency panels were not included in the definition of EPSS. So it was not clear to me whether you could put an emergency ATS and switchboard in the same room as a normal switchboard. That?s the issue, as I remember it. I don?t remember what we decided to do with that project.
 
Matt,

Section 7.2.2.1 of NFPA 110-2002 prohibits transfer switches that are part of a Level 1 system from being located in the same room with the normal electrical service equipment unless a minimum of twice the clearance required by 110.26(A) is provided. You are correct that this has been changed in the2005 Edition. I believe the intent of this requirement is to limit the possibility that a catastrophic failure of the service equipment will simultaneously damage the transfer switch. I don't have the 2005 Edition of NFPA 110 but I think this allowance was removed for equipment rated 1,000 amps or more and over 150-volts to ground.


It depends on the type of occupancy and the nature of the loads served whether or not this is a Level 1 system, but it appears the AHJ has already determined that it is.
 
Wow, I type to slow. The transfer switch is part of the EPS. Section 7.2.1 requires a separate room with a 2-hour fire-resistance rating (again for Level 1 systems) for EPS equipment. No other equipment is permitted in this room. The EPSS, in this case the generator, is permitted in this room.
 
charlie b said:
So it was not clear to me whether you could put an emergency ATS and switchboard in the same room as a normal switchboard.
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They made it easy for us here, they amended 700.9(D).

To much to type but all required generation and distribution equipment must be located in 2 hour fire resistant rooms and all emergency feeders as well. Realistically that means MI cable or other 2 hour fire resistant wiring methods
 
The generator is only for legally required standby power for the elevators. All lighting, security, fire, etc. has battery backup. The transfer switch is 480V, 3 phase, 400A. NFPA 7.2.2.1 does not clearly state if it applies to Level 1 or Level 2 or both? This hotel falls in the catagory of Level 2 according to IBC 2702.
 
Matt,

Yesterday I was pretty sure that the requirement applied only to Level 1 installations. Now I am not so sure (thanks alot). I am awaiting a call from NFPA. I will let you know when I get an answer.
 
RB1 said:
Matt,

Section 7.2.2.1 of NFPA 110-2002 prohibits transfer switches that are part of a Level 1 system from being located in the same room with the normal electrical service equipment unless a minimum of twice the clearance required by 110.26(A) is provided. You are correct that this has been changed in the2005 Edition. I believe the intent of this requirement is to limit the possibility that a catastrophic failure of the service equipment will simultaneously damage the transfer switch. I don't have the 2005 Edition of NFPA 110 but I think this allowance was removed for equipment rated 1,000 amps or more and over 150-volts to ground.


It depends on the type of occupancy and the nature of the loads served whether or not this is a Level 1 system, but it appears the AHJ has already determined that it is.
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I found this which backs up RB1
http://www.nfpa.org/itemDetail.asp?categoryID=1155&itemID=27188&URL=Publications/necdigest/necdigest%20Print%20Archives/October%202005/NFPA%20110%20Standard%20for%20Emergency%20and%20Standby%20Power%20Systems&cookie%5Ftest=1

Transfer switch locations are not addressed within the NEC, but are part of NFPA 110, with some specific location requirements for Level 1 equipment. Section 7.2.2 prohibits the installation of Level 1 transfer switches in the same room as normal service equipment where the service equipment operates above 150 volts to ground or the equipment load is equal to or greater than 1000 amperes.
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I think the 2005 can be viewed here

View the 2005 edition of this document.
 
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You guys are great. I would have never known that the rules have changed for ATS location. None of the cities call out NFPA 110 in their list of codes, but I wonder if since they enforce 2005 NEC, then would 2005 NFPA 110 be assumed, because it is referred to in the NEC??
 
RB1, any word on if it only applies to Level 1 installations? That is the last thing i'm not clear on. You guys are great, thanks for all the help!
 
mjaenke said:
RB1, any word on if it only applies to Level 1 installations? That is the last thing i'm not clear on. You guys are great, thanks for all the help!
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IMO level 1 as outlined here

Section 7.2.2 prohibits the installation of Level 1 transfer switches in the same room as normal service equipment where the service equipment operates above 150 volts to ground or the equipment load is equal to or greater than 1000 amperes.
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Ok now my next question is about the 2 hour fire rating feeders. For level 1 installations which feeders need the protection?

Generator to ATS?
ATS to Distribution Panel "EM"?
Feeders to emergency panels on all floors?
Feeders to the elevators (which is the whole reason for the generator)?
Feeders to devices supplying critical branch power (in the case of a hospital)?

Thanks!
 
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