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VFD working space? #215727 07/07/15 07:50 PM
Joined: Apr 2002
Posts: 189
triple Offline OP
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.

2017 / 2014 NEC & Related Books and Study Guides
Re: VFD working space? [Re: triple] #215728 07/07/15 07:52 PM
Joined: Apr 2002
Posts: 7,225
HotLine1 Offline
Based on what you say, IMHO I would say 'red tag'.

Re: VFD working space? [Re: triple] #215734 07/09/15 10:48 AM
Joined: May 2005
Posts: 984
ghost307 Offline
I tag.

Re: VFD working space? [Re: triple] #215834 07/25/15 08:50 AM
Joined: Sep 2002
Posts: 131
tsolanto Offline
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 08:52 AM.
Re: VFD working space? [Re: triple] #215835 07/25/15 08:51 AM
Joined: Sep 2002
Posts: 131
tsolanto Offline
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.

Re: VFD working space? [Re: triple] #215836 07/25/15 01:00 PM
Joined: Apr 2002
Posts: 7,225
HotLine1 Offline
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....



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