Non-conductive sheet to mitigate 110.26(A)(1) Condition 2

I

Isaiah

Senior Member
Location
Baton Rouge
Occupation
Electrical Inspector
We’ve discovered the distance from a 480V 200A, fused disconnect switch to the adjacent grounded surface (chain link fence) is barely 3’-0”. According to 110.26(A)(1) condition 2, this should be min 3.5’
Im looking for a clear conductive sheet to attached to the fence and reduce this distance to a condition 1. Has anyone done this before?


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Is a fence considered to be a grounded surface if there is no electrical connection to it? There are sections of the code where the fence is required to be grounded and bonded and it is not accomplished by merely being installed in the ground. For example 250.194.
 
infinity said:
Is a fence considered to be a grounded surface if there is no electrical connection to it? There are sections of the code where the fence is required to be grounded and bonded and it is not accomplished by merely being installed in the ground. For example 250.194.
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Good point. According to 250.194, this fence does not have to be bonded. Therefore it becomes a condition 1, correct?


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Last edited:
Isaiah said:
Good point. According to 250.194, this fence does not have to be bonded. Therefore it becomes a condition 1, correct?
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I would consider it condition 1 unless the fence was mechanically bonded to the electrical system.
 
infinity said:
I would consider it condition 1 unless the fence was mechanically bonded to the electrical system.
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There are zero electrical devices connected to the fence so I’m calling this condition 1.
Many thanks!


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I'm not ready to agree, not yet anyway. Since the fence is in intimate contact with planet Earth, it is every bit as "grounded" as a ground rod, a ground ring, a water pipe, or anything we use as "grounding electrodes."

Consider an electrician inadvertently touching a live part inside the switch. She is wearing rubber boots, so that a possible current path through her body into dirt will have a high resistance, and may not result in a significant shock. But if she backs into the fence, the rubber boots are no longer relevant, the resistance of the current path would be much lower, and potential shock would be greater.
 
Isaiah said:
I'm looking for a clear conductive sheet to attached to the fence and reduce this distance to a condition 1. Has anyone done this before?
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I have, many years ago.

A panel was to be installed on a mezzanine level that was between 36 and 42 inches from a handrail that was "grounded" by virtue of being built into concrete. We resolved the issue by covering the handrail with a rubber sheet.
 
charlie b said:
I'm not ready to agree, not yet anyway. Since the fence is in intimate contact with planet Earth, it is every bit as "grounded" as a ground rod, a ground ring, a water pipe, or anything we use as "grounding electrodes."

Consider an electrician inadvertently touching a live part inside the switch. She is wearing rubber boots, so that a possible current path through her body into dirt will have a high resistance, and may not result in a significant shock. But if she backs into the fence, the rubber boots are no longer relevant, the resistance of the current path would be much lower, and potential shock would be greater.
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Actually the fence is not intimately into the earth itself. it is mounted on top of the concrete containment curb


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Isaiah said:
Actually the fence is not intimately into the earth itself. it is mounted on top of the concrete containment curb


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For the purposes of shock protection and 110.26(A), I would see that fence as a grounded surface and a condition 2 location.
 
charlie b said:
I'm not ready to agree, not yet anyway. Since the fence is in intimate contact with planet Earth, it is every bit as "grounded" as a ground rod, a ground ring, a water pipe, or anything we use as "grounding electrodes."

Consider an electrician inadvertently touching a live part inside the switch. She is wearing rubber boots, so that a possible current path through her body into dirt will have a high resistance, and may not result in a significant shock. But if she backs into the fence, the rubber boots are no longer relevant, the resistance of the current path would be much lower, and potential shock would be greater.
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I thought step touch bonding was not a NEC requirement unless you have a swimming pool, agricultural building or man made pond


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Dale001289 said:
I thought step touch bonding was not a NEC requirement unless you have a swimming pool, agricultural building or man made pond


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It doesn't, that is why 110.26(A) specifies an increased working space where the surface opposite the equipment is a ground surface. Charlie was just pointing out a reason for the increased working space with a ground surface opposite the equipment.
 
Isaiah said:
Actually the fence is not intimately into the earth itself. it is mounted on top of the concrete containment curb


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If this is the case, how do you know that one or more of the attachment anchors are not touching any rebar in the slab?????
the path to ground should at a minimum be tested before saying there is no path to ground, connected to the fence.
 
acrwc10 said:
If this is the case, how do you know that one or more of the attachment anchors are not touching any rebar in the slab?????
the path to ground should at a minimum be tested before saying there is no path to ground, connected to the fence.
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The fastening hardware is 1/4” SS and not anywhere close to the rebar.


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don_resqcapt19 said:
The code says a masonry wall is a grounded surface. I stand by my statement that a metal fence attached to concrete is also a grounded surface.
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Looks like we need to add a rubber sheet (or similar) like mentioned above
But how large would the sheet need to be? I’m thinking at least 30” wide directly opposite the switch…
And from the bottom of the fence to the top (or 6.5’ min)


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