UPS GROUNDING

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sam34

Member
Hello every one, I have an 80kva UPS (480-120/208V) that would be installed in a computer room. Should I treat it as seperatly derive system since it has built in transformer? In another word should I connect the Y side to the building steel?? your input is really appreciated..
 

dereckbc

Moderator
Staff member
Re: UPS GROUNDING

Byron, why do you feel 645.12 exempts you from running a GEC to an isolation transformer?
 

petersonra

Senior Member
Re: UPS GROUNDING

Originally posted by bwilson:
No. Take a look at 2002 645.15 NEC
Byron
Basically all this does is allow the incoming EGC to serve as the grounding electrode. It's still an SDS.
 

bwilson

Member
Re: UPS GROUNDING

645.15 ... Power systems derived within listed information technology equipment that supply information technology systems through receptacles or cable assemblies supplied as part of this equipment shall not be considered separately derived for the purpose of applying 250.20(D)......See the FPN #1

250.20(D)does not apply in a ART.645 room. 250.20 permits in the 2nd sentance to ground the system if you want. If you do you must comply with all of 250.20.

Do you not aggree.
 

don_resqcapt19

Moderator
Staff member
Re: UPS GROUNDING

Just because the room is called a "computer room" does not make it an Atricle 645 installation. It is only such if all of the items listed in 645.2 are complied with.
Don
 

don_resqcapt19

Moderator
Staff member
Re: UPS GROUNDING

bwilson,
A stand alone UPS, even when installed in an Atricle 645 installation, is not a "power systems derived within listed information technology equipment" and 645.15 does not apply.
Don
 

dereckbc

Moderator
Staff member
Re: UPS GROUNDING

Originally posted by bwilson:
645.15 ... Power systems derived within listed information technology equipment that supply information technology systems through receptacles or cable assemblies supplied as part of this equipment shall not be considered separately derived for the purpose of applying 250.20(D)......See the FPN #1 Do you not aggree.
No I do not. That would mean the UPS, receptacles, and distribution would all have to be self contained in a UL package box like the ones you buy at a box store and plug your PC into.

UPS systems used in Data centers I work with are sized from 80KVA to 800KVA remotely located in a mechanical/electrical/battery room and use premise wiring methods.
 

bwilson

Member
Re: UPS GROUNDING

I understood from the original question (perhaps Wrong) that this was a Art. 645 room. Have also seen many PDU sized from 45 to 150 KVA with listed cable assemplies to supply power to differant equipment. The point is that 645.12 allows you to have a ungrounded supply system for this equipment if you follow all the rules in Art. 645. To make a blanket statrment that all such systems must be grounded is wrong. It all depends on the intended design.
Byron
 

brian john

Senior Member
Re: UPS GROUNDING

Depends on if there is a separate bypass. If there is a 208/120 VAC wye bypass and the neutral for the bypass is grounded then NO, if the neutral for the bypass is not grounded then YES. If there is no separate bypasss at 208/120 or the bypass is at 480 then NO.
 
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