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#174671 - 02/11/08 08:32 AM raised floor grounding
jrvazzer Offline
Junior Member

Registered: 10/24/05
Posts: 4
Loc: ny,ny usa
Does the NEC have grounding requirement for raised floor in genral office space not IT or Data center.
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#174673 - 02/11/08 08:54 AM Re: raised floor grounding [Re: jrvazzer]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
No but your IT guy probably does. The only time the NEC would be involved is if you said it was "likely to be energized". (you do need the bezels on penetrations)
IT folks still want it grounded for noise suppression reasons.
Also note 645.2 and understand that most of the things you can get away with in a real data center under the floor is limited to that occupancy. Once you leave the computer room you lose a lot of that leniency. This becomes important when they convert old computer room space to office space. You should really be blocking off the HAVC between them and leaving a lot of that "free fire zone under the floor" mentality behind. I have seen AHJs who wanted all solid tiles installed and absolutely no wiring under the floor that wasn't in a chapter 3 wiring method.
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#174674 - 02/11/08 09:26 AM Re: raised floor grounding [Re: gfretwell]
jrvazzer Offline
Junior Member

Registered: 10/24/05
Posts: 4
Loc: ny,ny usa
Thanks for you respond.
We have a situation, where the tenant wanted to do renovation to his floor. (Not the first time) The floor is raised about 6" no HVAC just power and tel com wiring. The AHJ notice that the floor was not grounded, and mentions that the raised floor should be grounded. This tenant has occupied this facility for about 15 years. Is he forced to pay for the grounding of this floor base on IT requirements or NEC or is it AHJ. Their are 50 other floors in this building all having raised floors. Now, at this renovation the AHJ wants us to ground this floor.
One contractor quoted a high price for this work, other are quoting a smaller amount. The question is what requirement or standards do we use to properly design and satisfied AHJ and also have a uniform drawings so that all contractor can be on the same page when biding.
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#174701 - 02/11/08 08:28 PM Re: raised floor grounding [Re: jrvazzer]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
Does the AHJ want old time system 390 level bonding with 2 gauge or larger copper to every post or is he just looking for a EGC from the wiring method under the floor to one or two places in the floor in some misguided reading of 250.104?
I would want to hear the article he is citing.
I think you should be able to go right from a metal box on each circuit to the floor, using the "circuit likely to energize" logic.

Around here the real question would be what is under that floor and how are you getting up into the office? Stringing power cords through floor penetrations is not compliant as soon as you leave article 645 space.
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#174721 - 02/12/08 11:15 AM Re: raised floor grounding [Re: gfretwell]
ggardiner Offline
Member

Registered: 10/22/01
Posts: 81
Loc: Calgary, Alberta Canada
Check with the flooring manufacturer for their recommended grounding instructions they may have the paper work to prove it does not need grounding in your area, or what the minimum requirement mght be. Even a 15 year old floor should be able to track down. I get requests all the time for grounding details for raised flooring that my company builds.

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#174722 - 02/12/08 11:33 AM Re: raised floor grounding [Re: gfretwell]
jrvazzer Offline
Junior Member

Registered: 10/24/05
Posts: 4
Loc: ny,ny usa
Thanks. I could have asked him that but I didn't want to make it worst. I agree that there should be grounding, but to what extend. The floor is also being carpet so there is little chance of making contact with an energize floor.
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#174730 - 02/12/08 03:13 PM Re: raised floor grounding [Re: jrvazzer]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
Is this a stringer floor or just posts? A bolted together stringer floor could be grounded with a single wire.
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Greg Fretwell

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#174768 - 02/13/08 06:02 AM Re: raised floor grounding [Re: gfretwell]
jrvazzer Offline
Junior Member

Registered: 10/24/05
Posts: 4
Loc: ny,ny usa
Yes, thanks that is exactly what the AHJ accepted.
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jrv

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