concrete encased service feeders within a building

[mshields]

I'm working on a high rise project where the service equipment (S&C gear plus two pad mounts) is located in a vault on the second floor of the building. We are running through the garage in a concrete encased primary feeder all inaccordance with the NEC. Some of this duct is supported by steel structural elements specifically installed to support the duct (the building itself is actually concrete). The architect is questioning whether or not these steel supports should be fire proofed with the spray on stuff. My response is as follows. I'd be interested in your insights - thanks


My response:
I don't see anything in National Grid's special provisions nor in their general requirements, requiring fire proofing of supports for the concrete encased primary lines in the building. It does nevertheless strike me as consistent with the rational behind requiring concrete encasement to begin with. This an NEC requirement by the way, not the utilities.

The reasoning is that whereas the rest of the building can be de-energized from the service disconnect switches within the building this primary leg cannot be.

You are therefore left with a scenario where the Fire Department does not have a means of de-energizing this one component within the building. It is therefore required that this feeder be made bullet proof or more to the point, fire proof to reduce the chances of it rupturing and electrocuting someone. If the support for the busduct is not fireproofed, then it stands to reason that neither is the duct itself.

I do not know of nor can I find a specific mention of this in the NEC. Still, I think it should be done.

 

[Smart $]

TTBOMK , steel IS fireproof. Therefore, IMO, spray-on fireproofing is unnecessay. However, steel is not heat proof. Any steps to improve structural integrity before, during, and after a fire would be a more worthwhile objective.

 

[iwire]

TTBOMK , steel IS fireproof. Therefore, IMO, spray-on fireproofing is unnecessary.

Glad you could point that out.

However, steel is not heat proof. Any steps to improve structural integrity before, during, and after a fire would be a more worthwhile objective.

And that process is called fireproofing, it is installed by a fireproofing contractor.

www.albi.com

 

[Smart $]

Oh, I know what it is called. I didn't see any mention of heat refracting or the concept of increased structural integrity mentioned anywhere on the site you referenced (but I only glanced at the home page). I'm sorry, but I do not equate fireproofing with any measures to add a heat refractory or enhance structural integrity. I can't help it if others do!

 

[mhulbert]

mshields,

It is rare to see raw, uncovered red iron in a high rise. I would go along with the fireproofing because, IMO, if it were involved in a fire, you would not only have the electrical hazards, but also the aspect of a concrete beam falling down as well. That would be a giant booby trap for a firefighter. Get knocked on the head witha beam, then electrocuted after it splits open.

I would strongly recomend fireproofing. If you need more ammo, I think you will find it in the applicable building code that covers this project, especially if it is in fact Type I/II construction.