Working space question: 480V VFD facing 480V Mechanical Air Handling Unit (AHU)

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fandi

Senior Member
Location
Los Angeles
Hello All,
We have 42" clearance between the VFD and the AHU. They're front facing each other. We run out of room to relocate the VFD. Per NEC Table 110.26(A)(1), Condition 2 needs 42" whereas Condition 3 needs 48".
Is 42" sufficient in this case?
Thanks.
 

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Sorta retired........
Hello All,
We have 42" clearance between the VFD and the AHU. They're front facing each other. We run out of room to relocate the VFD. Per NEC Table 110.26(A)(1), Condition 2 needs 42" whereas Condition 3 needs 48".
Is 42" sufficient in this case?
Thanks.

No, according to what I see in the explanatory exhibit 110.12 2014 NEC.
you need 48 inches.
 

fandi

Senior Member
Location
Los Angeles
No, according to what I see in the explanatory exhibit 110.12 2014 NEC.
you need 48 inches.
But that same exhibit 110.12 (2011 though) shows permitted reduction from Condition 3 to Condition 2 according to 110.26(A)(1)(c) for existing buildings as long as they are not being open at the same time.
 

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Sorta retired........
But that same exhibit 110.12 (2011 though) shows permitted reduction from Condition 3 to Condition 2 according to 110.26(A)(1)(c) for existing buildings as long as they are not being open at the same time.

You are correct. I did not read far enough along in the article.
Are you replacing equipment or trying to get something in a space that didn't have anything in it before?
 

fandi

Senior Member
Location
Los Angeles
You are correct. I did not read far enough along in the article.
Are you replacing equipment or trying to get something in a space that didn't have anything in it before?
It's an existing building. If it was new, I would designate 48" clearance and be done with it.
Anyway, I need to have contractor put a sign with the wording as the exhibit suggests.
 

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Sorta retired........
It's an existing building. If it was new, I would designate 48" clearance and be done with it.
Anyway, I need to have contractor put a sign with the wording as the exhibit suggests.

Unless you are replacing existing equipment I don't believe you can reduce the clearances required.
110-26.1.(c) Existing buildings. In existing buildings where electrical equipment is being replaced, condition 2 working shall be permitted between dead-front switch boards,
switchgear, panel boards or motor control centers
 

fandi

Senior Member
Location
Los Angeles
Unless you are replacing existing equipment I don't believe you can reduce the clearances required.
110-26.1.(c) Existing buildings. In existing buildings where electrical equipment is being replaced, condition 2 working shall be permitted between dead-front switch boards,
switchgear, panel boards or motor control centers
Yes, the AHU is being replaced.
 
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