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

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fandi

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Los Angeles
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Electrical Engineer
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.
 
fandi said:
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.
Click to expand...

No, according to what I see in the explanatory exhibit 110.12 2014 NEC.
you need 48 inches.
 
qcroanoke said:
No, according to what I see in the explanatory exhibit 110.12 2014 NEC.
you need 48 inches.
Click to expand...
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.
 
fandi said:
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.
Click to expand...

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?
 
qcroanoke said:
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?
Click to expand...
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.
 
fandi said:
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.
Click to expand...

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
 
qcroanoke said:
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
Click to expand...
Yes, the AHU is being replaced.
 
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