NEC Working space clearances 110.26

[Eng]

I have a situation where the RTU was installed too close to the edge of the roof. This is causing the building inspector to required a guard rail be installed and reduces our working space from 42" to 38" from the front of the VFD. This is a 480V 3P system.

My question is, what condition does this fall under? Is the guard rail considered grounded parts and requiring us to have 42" clear? or is the guard rail considered to be no grounded parts and requires us to be at 36".

I have not contacted the inspector as we do not have a solution yet.

Thanks.

 

[ron]

I would guess that metal guard rail is obvious when Condition 2 also includes concrete brick or tile to be considered grounded.

Maybe the guard rail can be fiberglass or PVC rail? That would put you in Condition 1 for 36".

 

[charlie b]

I onced resolved a similar issue by permanently wrapping the railing with a non-conductive material. That put the installation into Condition 1.

 

[Eng]

I onced resolved a similar issue by permanently wrapping the railing with a non-conductive material. That put the installation into Condition 1.

Thanks. we are looking into doing this if the architect agrees. We will be bringing ths up with the AHJ to get his take on it.

FYI: The metal railing is a ballasted railing that will be set on the rubber roof membrane and will not be connected to any parts of the building. This may put it as condition 1 even with it being metal.

Thoughts.

 

[charlie b]

Being metal is not the issue. Having a path (of whatever resistance) to planet Earth is the issue. Recognizing that a concrete wall is considered a grounded surface in this context, you have to make a concerted effort to ensure that there is no way that the metal railing would have a path to Earth. If there is rubber insulation between the rail and the roof, that would be fine. But how would the railing be fastened? If you use metal nails or screws that pass through the rubber insulation into the wood or other material of the roof, you establish a path to ground (again, at least in the context of this code requirement). It would be better if the railing were not made of a conducting material.

 

[north star]

= =

The inspector is correct!......See Section 304.10 in the `06 IMC.
Also, ...that Guard Rail will need to meet the loading requirements
to prevent someone who is working on that equipment, from
accidently falling off of the roof......Not sure of or familiar with
the "ballasted means of anchoring" the Guard Railing.......I'm
thinking that it will need to be fastened to the structure in an
approved manner.....Contact the AHJ for guidance.

= =

 

[Eng]

Thanks for the assistance. The Architect is working with us and will move the guard rail, anchoring it to the top of the parapit, leaving us with 43" clear.