Working Spaces (NEC 110.26)

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jrohe

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Professional Engineer
What depth of working space would be required for 277/480V switchgear that is mounted on one wall of an electrical room when 120V, grounded convenience receptacles are mounted on the opposite wall?

The definitions of "exposed (as applied to live parts)" and "live parts" in Article 100 leads me to believe that the contacts of the receptacle would cause this installation to fall under Table 110.26(A)(1), Condition 3, requiring the depth of the working space to be 4'-0". However, an associate has argued that because the 120V convenience receptacles are grounded, Condition 2 would apply and the working space would only be required to be 3'-6" deep.

Jason
 
dcspector and C3PO,
I apologize, but I'm having trouble following where 3'-0" might be allowed. The room has live parts on both sides of the room. 277/480V switchgear on one wall and 120V receptacles on the other wall. There is nothing in the middle of the room insulating these two walls from one another.
 
dcspector said:
Answer.....3' working clearance.
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C3PO said:
That is my answer as well.
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Three feet cannot be the answer. There is a 480/277 volt switchgear, and that puts us in the second row of the table (151 to 600 volts to ground).

My answer is 3.5 feet. I presume the wall opposite the switchgear is to be treated as a grounded surface, and that puts us into Condition 2. I do not consider a receptacle to be ?exposed live parts.?
 
jrohe said:
The room has live parts on both sides of the room. 277/480V switchgear on one wall and 120V receptacles on the other wall.
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I have never encountered any design that provides working clearance in front of 120 volt receptacles, nor have I heard of any inspector who would require such clearances. Perhaps it can be justified by the assertion that receptacles are not likely to require maintenance while energized (which would mean that 110.26 does not apply). But in a practical sense, I don't see having one electrician working inside the switchgear while another electrician has a live receptacle dangling outside the outlet box on the opposite wall.
 
Charlie,

I do not see 3-1/2' 277v to ground. Ok....Condition one insulated material on one side and exposed live parts on the other....3' working clearance is required. Condition 2 grounded parts on one side and grounded parts on the other.:-?
 
I was thinking 277V to ground condition 1 which would be 3'.

IMSO, by definition, a receptacle is not considered an exposed live part.
 
augie47 said:
my thinking would be along the line with Chalieb, 3' 6".
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So what is insulated material under condition 1? Grounded parts are concrete, brick, tile under condition 2. I am not disagreeing just want to get on the same page.
 
dcspector said:
Condition one insulated material on one side and exposed live parts on the other....3' working clearance is required.
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I almost never see "Condition One." There is almost always some kind of wall, or handrail, or pipes, or motors, or some other component across from the panel. All of these count as being grounded, and that puts you into "Condition Two."
 
dcspector said:
So what is insulated material under condition 1? Grounded parts are concrete, brick, tile under condition 2.
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I have a project in which panels will be installed along a catwalk in the interstitial area above a laboratory floor. The catwalk is 40 inches wide, and the voltage level to ground is 220 volts. As you stand in front of a panel, and start walking backwards, you will back into a handrail on the opposite side of the catwalk. Thus, you have at most 40 inches of working space available. Under Condition 2, at 220 volts to ground, you need 42 inches. That sets up a code violation.

My solution is to wrap a sheet of rubber around the handrail, and permanently glue it into place. This way, the surface opposite the panel will not have any live or grounded parts. That gets me into Condition One, and I only need 36 inches of working space.
 
dcspector said:
So what is insulated material under condition 1? Grounded parts are concrete, brick, tile under condition 2. I am not disagreeing just want to get on the same page.
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greg, I drew a mental picture ( a mistake with my mind) and pictured conduit to the receptacle (probaby because I'm so accustomed to that on 480/277)... but, in hindsight, if it's a non-grounded wall with recessed receptacles, I would accept 3'.
 
augie47 said:
. . . in hindsight, if it's a non-grounded wall with recessed receptacles, I would accept 3'.
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I would also, IF IF IF IF IF the wall were non-grounded. But I sincerely doubt that that is the case. :smile: :smile: Almost any wall you could name would count as being grounded.

So, Jason, can you tell us the material of construction of the wall that is opposite the switchgear?
 
The wall is concrete, so it would be considered grounded under condition 2. However, my concern lies in whether the contacts of the receptacle would be considered "exposed live parts." Condition 2 does not list any provisions for "exposed live parts" on both sides of the working space.
 
jrohe said:
The wall is concrete, so it would be considered grounded under condition 2. However, my concern lies in whether the contacts of the receptacle would be considered "exposed live parts." Condition 2 does not list any provisions for "exposed live parts" on both sides of the working space.
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Since the wall is concrete then I change my answer to condition 2 (3' 6")

Exposed (as applied to live parts) : Capable of being inadvertently touched or approached nearer than a safe distance by a person. It is applied to parts that are not suitably guarded, isolated, or insulated.

I still do not consider a receptacle to be an exposed live part.
 
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