PVC floor box in a place of assembly

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dedbrk

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I have a mortuary chapel with PVC conduit in the slab feeding PVC floor boxes all of which is slab on grade. 518.4(C)1 states where concealed in floors with a 15 minute finish rating I can do this. Am I incorrect in assuming this? We plan on using brass covers. For the life of me I cannot find a UL listing for fire ratings on a standard floor box. I can find UL fire ratings on poke thru floo boxes all week long, but nothing on standard floor boxes. I can only assume that if a poke thru box is rated for 2 hours with a brass cover then surely a floor box in slab on grade with a brass cover would be the same. I can't find documentation of such. Am I heading in the wrong direction? Any help would be greatly appreciated. Most situations don't turn out favorable when I start assuming things:)
 
A slab on grade is not required to be of fire-resistance-rated construction. Rigid nonmetallic conduit is permitted to be installed in these areas per 518.4(B).
 
I started to agree until I did a little more research.

The roof, walls, and floor of the building are combined to make this a one hour building. You can run the PVC conduit in the slab, but once you penetrate that membrain then you are required to use a listed product.

I'm sure what the inspector wants to see is that it is a listed floor box with a minimum 1 hour rating.

I couldn't find anything in the information I had on floor boxs that said they were rated, but I didn't look at the UL info either.
 
I did a lot of research on the UL website and couldn't find a listed fire rating for regular floor boxes, but as mentioned earlier I did find multiple listings for poke thru's.
 
John,

Can you elaborate on your research. Usually rated construction is provided to prevent the passage of heat and smoke. The slab can only be exposed to fire on one side, and from there it is not going anywhere.

I guess this could bring new meaning to the scorched earth policy.
 
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RB1 said:
John,

Can you elaborate on your research. Usually rated construction is provided to prevent the passage of heat and smoke. The slab can only be exposed to fire on one side, and from there it is not going anywhere.
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I actually asked our Deputy BO / Chief Planchecker.

I will say that I don't disagree with you, but you're not always just looking at flame, you also have to think about toxic smoke.

You can use nonmetallic conduit per 518.4, but look at the restrictions. So I'm thinking that they don't want the plastic exposed, but even then I still may not have entirerly convinced myself.

OK after typing the above I asked around some more. One of our inspectors said that the OP should ask for the fire rating of the concrete used in the slab. His point is that no matter whether you build a one hour, or two hour building on it, the concrete is always the same.

So far, after further questioning, it's 2 inspectors that both say it's not required to be rated and 2 engineers that say they would at least question it.
 
John,

I think this discussion is interesting. The OP is referencing a code section that restricts the use of certain wiring methods. I agree that the rationale for the restrictions are to limit the amount of smoke and toxins during a fire event and allow the necessary time to evacuate the building. In this case the conduits probably could be considered outside of the building. In light of that I don't see any restrictions in Article 518 that relate to outlet boxes. If these outlet boxes were penetrating the membrane of a rated assembly Section 300.21 would address that issue.
 
RB1 said:
John,

I think this discussion is interesting. The OP is referencing a code section that restricts the use of certain wiring methods. I agree that the rationale for the restrictions are to limit the amount of smoke and toxins during a fire event and allow the necessary time to evacuate the building. In this case the conduits probably could be considered outside of the building. In light of that I don't see any restrictions in Article 518 that relate to outlet boxes. If these outlet boxes were penetrating the membrane of a rated assembly Section 300.21 would address that issue.
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After thinking about it more, I agree with you.
 
actually, i've never had to deal with floor outlets and the fire rating. but reading the posts drew my interest to learn something new so i started googling for fire rated pvc boxes, etc. wish i knew more to help.
 
Have you tried going back to the supply house, or manufacturer to see if they have any rating info. for your box, or any other?

I also know 3M makes a putty for electrical (outlet / switch) boxes that might be acceptable to the inspector if you're pushed on it.

-Dan
 
When the building code delineates fire rated assemblies for the envelope of a building, including floors, are the said floors mentioned concrete on slab?


I am taking an educated guess and saying no. The box in the floor is not penetrating a fire rated assembly and in my opinion would itself not require listing with a fire rating, it would need listing as a floor box.

JMHO
 
Pierre C Belarge said:
When the building code delineates fire rated assemblies for the envelope of a building, including floors, are the said floors mentioned concrete on slab?


I am taking an educated guess and saying no. The box in the floor is not penetrating a fire rated assembly and in my opinion would itself not require listing with a fire rating, it would need listing as a floor box.

JMHO
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Pierre,

I think that's what we've all come to as a conclusion as well.

Now he just has to convince the AHJ that he's working with.:)
 
I do have Carlon helping me out on this. They did say that there is no rating on these boxes, but had a consultant with an extensive background in building codes, fire ratings and NEC. I'm actually very excited to see what he has to say. Talked to him on the phone and he was very confident that he could provide documentation to the AHJ that there is no rating required.

Most engineers that have been approached about this (T&B, Carlon) were very surprised in the question and have never had to provide this. That was a large red flag to me. The biggest task at hand is trying to convince AHJ that this is an approved method of installation. Sometimes it feels that self amputation of a limb would be an easier task:)
 
I think that's a great way to go.

Sometimes as inspectors even we need someone else to look at it and convince us.

I even tried to support the inspector, but the more I looked at it the less convinced I was that he was right.
 
I just got a lot of info from a company that Carlon uses to conduct fire investigations and development of installation methods for their products (FCA Fire). Way too much good information to post, but in short he says that a "Finish Rating" in general is for cavity walls and floor/ceiling assemblies and has been adapted to other applications to describe the performance of protective membranes. He continues to state that a finish rating does not apply to this installation because the assembly (concrete) is both non-combustible and has no cavity. Finish ratings are measured from the backside of a protective membrane and thus not being able to find any listed rating on the floor boxes in the slab.

Basically, he is a very experienced and knowledgeable individual who feels this is a proper installation and will provide all documentation needed to prove it. Now all I can do is sit back and wait for the AHJ's interpretation. It should definitely help having a report from a fire investigation company and it's author with a Ph.D. stating the box will perform just as well in the concrete.

Thanks for everyone?s help.
 
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