13.2kV code required clearances

[futureshock]

Let me start by saying I love this forum. I'm new ... be gentle.


The code inspector on our project stated 110.34 as the reason for requiring 5 feet of clearance in front of the sub-station (13.2kV primary switch feeding 300kVA 13.2kV to 208V xfmr and 800A panel).

When I read 110.34 it states ?equipment likely to require examination, adjustment, servicing, or maintenance while energized shall have??. The EC said they would never open that enclosure while energized, and there is an upstream switch, so to me those distances do not apply and we revert back to 110.26, condition 2, which requires 3 feet.

Our EE is traveling but confirmed 5 feet is required but did not reference which code section required it. Is 5 feet just the accepted industry standard or do I need to be referencing another section.

Thanks.

 

[charlie b]

I think it is generally accepted that the phrase “likely to require” means more than it says. However “unlikely” you may think it would be for anyone to open an enclosure live, the presumption is that it might happen someday. That simple notion of “it might happen” is all it takes to bring you into the working clearance rules. Put another way, if you cannot prove right here and now that it is physically impossible for the enclosure to ever be opened when its contents are live, I am going to declare forever hereafter that it is “likely to require” live work someday. Telling me that you have strict company rules that forbid live work is not enough. Telling me that you have enough respect for electricity that you would never open that box live is not enough. Prove to me that you have an interlock that will turn off power to the box if a person walks within 10 feet of its front face, and I might go along. You can try to fight city hall on this one, but you are not likely to win.

That said, do I understand correctly that you have two enclosures opposite from each other, one at 13.2kV and the other at 208/120V? If so, then I think you are in Condition 3, and table 110.34(A) puts the working clearance at 6 feet.

Welcome to the forum.

 

[futureshock]

Thanks Charlie. I'm certainly not interested in fighting city hall, just needed personal enlightenment. I was beginning to think clearances for the 13.2kV cabinet were addressed elsewhere in the code.

Seems my thinking was on the wrong side of "likely". Thanks for the shift in perspective.

Interesting interlock solution ... maybe I include it in the spec and wait for the RFI's!

Thanks,

Paul

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So much to learn ... so little time.