300.22 Wiring in Ducts, Plenums, and Other Air Handling Spaces

[Akranz2]

I am currently in process of designing a new electrical box molded from plastic for use in a drop ceiling and got to thinking about not being able to run PVC above a drop ceiling used for plenum purposes... Flipped the code book open and found it in section 300.22(C) which states "Other Space Used for Environmental Air." with a Fine Print Note below it specifying exactly Drop Ceilings used as a Plenum space..

300.22(C)(1) Wiring Methods states basically conduit with an overall nonmetallic covering is not allowed same with cable unless its listed for use as a Plenum, nothing about boxes..

300.22(C)(2) Equipment. Electrical equipment with a metal enclosure, or with a nonmetallic enclosure listed for the use and having adequate fire-resistant and low-smoke-producing characteristics..

Now the question if it falls under 300.22(C)(2) what would be considered adequate fire-resistant and low-smoke-producing characteristics?

Does that apply to any types of plastic if so any insight to where I may find this information?

Thanks and is greatly appreciated

 

[raider1]

300.22(C)(3) (2011 NEC) would require that the plastic box be listed for use within an air handling space. This section is located in 300.22(C)(2) in the 2008 NEC.

The 2011 NEC has clarified that the nonmetallic enclosure must be listed for use within an air handling space.

Chris

 

[Akranz2]

Thanks for the response Chris it is greatly appreciated but I was actually there and looking for what those requirements would be as far as material to make the box out of.

Thanks again,
Andy

 

[Dennis Alwon]

Thanks for the response Chris it is greatly appreciated but I was actually there and looking for what those requirements would be as far as material to make the box out of.

Thanks again,
Andy

Are you trying to make your own compliant box? I would contact UL to see what there guidelines would be.

 

[raider1]

Thanks for the response Chris it is greatly appreciated but I was actually there and looking for what those requirements would be as far as material to make the box out of.

Thanks again,
Andy

As I read 300.22(C)(3) (2011 NEC) The non-metallic enclosure would have to be listed so you could not just manufacture your own box unless you pay to have it listed.

Chris

 

[Dennis Alwon]

As I read 300.22(C)(3) (2011 NEC) The non-metallic enclosure would have to be listed so you could not just manufacture your own box unless you pay to have it listed.

Chris

That is why I suggested talking with UL or some other 3rd party testing. I agree totally you cannot make your own box without getting it listed.

 

[Akranz2]

Yes I am actually making the box. Have cad model of it and everything ready to be made into a prototype. I have had several talks with UL about it and even a quote from them to test it for electrical but they have no idea what type of material it should be made of. They just test it is all they do according to the few that I talked with there.

This hunt has me running around. I actually talked to a chemical engineer today about it and I am getting ready to do research on fire resistant polymers. According to him though to make it "low smoke" they just add more filler in and less plastic which I think may weaken the box and not work.

 

[Dennis Alwon]

Good luck. The NEC will be no help I'm afraid.

 

[Akranz2]

Well thank you for all your help and it's looking a lot more positive. It's looking like they can make about any plastic fire retardant by adding in this other resin with it.

So all in all my understanding is the box will be compliant as long as it meets the fire retardant and low smoke producing characteristics which will be tested by UL who I just got off the phone with again. Guess the 10,000 dollar quote just went up for plenum testing now being added to the quote. Luckily an engineer will be calling me to explain how they will test it sometime, going to get as much free info from them as possible ha ha.

Thanks again for all the help