transformer accessisibility

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powermac36

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An electrical contractor wants to hang a 75 KVA xfrmr above a suspended ceiling area (non-plenum rated)-

article 450.13(B) accessibility to xfrmrs in hollow spaces (not permanently closed in by structure, ventilated, and fire resistent barrier)

My question is: is the area above a suspended ceiling a permanently enclosed hollow space?
 
Re: transformer accessisibility

Originally posted by powermac36:
My question is: is the area above a suspended ceiling a permanently enclosed hollow space?
Click to expand...
No, it is not permanently closed in by structure.

However it does not matter as you can not install a 75 KVA up there, you are limited to 50 KVA and smaller above suspended ceiling.
 
Re: transformer accessisibility

I was originally thinking that section wasn't describing suspended ceilings, but I guess after reading it three more times it is. I guess.

Weird phrasing, IMO.
 
Re: transformer accessisibility

Other than reading article 100. How can I define if the area above the ceiling in my work area is plenum rated? There is duct work above the ceiling but it is all connected, I do believe the area is used as a cold air return. I can wire a 480V PDU in my data center but I don't know a thing about air conditioning. Can anyone help?

Thanks,
Kevin
 
Re: transformer accessisibility

Look for open registers or grills in place of a ceiling tile (no ducts connected to them). "plenum"
Look at the registers. Supply will have vanes where as returns will not. Then check above for ducts connecting to each of them. not a "plenum"
Look for exposed wood above the ceiling. not a "plenum"
Sometimes luminaires are used for return grills.
 
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