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#215727 07/07/15 08:50 PM
Joined: Apr 2002
Posts: 197
T
triple Offline OP
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Does 110.26(A) apply to variable frequency drives controlling hvac related pumps? The wording of the article (and the commentary in the NEC Handbook) definitely seems to suggest that vfd's require working space. However, the electrical inspector is allowing them to be buried behind the motors and pumps. "Examining, adjusting, serving, and maintaining" these "controls" for "heating and air-conditioning equipment" now requires standing over/on or straddling the motor/pump unit.

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Joined: Apr 2002
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triple:
Based on what you say, IMHO I would say 'red tag'.



John
Joined: May 2005
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I agree...red tag.


Ghost307
Joined: Sep 2002
Posts: 131
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Member
I looked through 430 to see if there were any exceptions for Adjustable Speed Drives. I could not find any. So, IMO 110.26 applies.

"430.120 General. The installation provisions of Part I
through Part IX are applicable unless modified or supplemented
by Part X."


I could not find anything in Part 1 through 10 to suggest anything with regards to working space. I would have hoped that it pointed you to 110.26 at some point but it does not.

Some people consider a VFD a motor control center and if you look at it that way you would need to comply with 110.26F. I don't believe that it is a MCC since there is a clear section in 430.120 specifically providing rules for Adjustable Speed Drives (VFD's)...

IMO 110.26 A as you suggest is the winner.

Last edited by tsolanto; 07/25/15 09:52 AM.
Joined: Sep 2002
Posts: 131
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All that being said, here in NYC believe it or not we are still on the 2008 NEC so my commentary is based on that. I don't know which edition you are working with, not sure if it would matter in this case either.

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IMHO, there are no differences within '11 or '14 regarding this.

NJ is still on'11, and I don't recall anything from '14 from "the changes" although I still admit to have a lot of reading....



John

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