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#78426 - 09/22/01 08:13 PM Re: Working Clearance for HVAC Equip
Bill Addiss Offline

Registered: 10/07/00
Posts: 4196
Loc: NY, USA
From the 'Mailbag'
I have installed a 7 1/2 ton split system air conditioning unit in an electrical/communication room. It is 460 V 3 phase. According to the UMC I need to have a 30" X 30" clear access for where the power is tied into the unit and for controls. I have an inspector who is saying that I must go by the NEC and have 30" X 42" clear access, due to the voltage. Can you help me out.

2014 / 2011 NEC & Related Books and Study Guides
#78427 - 09/23/01 07:53 AM Re: Re: Working Clearance for HVAC Equip
electure Offline


Registered: 12/24/00
Posts: 4226
Loc: Fullerton, CA USA
Your inspector is correct if you have a grounded surface on the opposite side of the workspace.
NEC 110-16 deals with working clearances.
Table 110-16(a) gives the working clearances as they apply do different situations.
At 151-600V to ground, the clearances are:
1)No live or grounded parts on other side=3'
2)Grounded parts on the other side=3-1/2'
3)Live parts on both sides=4'

In any case, the 30" in the UMC is not sufficient by NEC, as the requirement at 0-150V is 3' in any of the conditions mentioned above.


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