why one and not the other?

[copper chopper]

For those inspectors and engineers out there, I would like to know why according to 300.22 in the NEC. Pvc conduit is not allowed in a plenum ceiling, however why then is plumbing pvc and cpvc allowed in the same space. Arnt they the same schedule 40 type just different color.. Maybe some of you have a co-worker who is a plumbing inspector that could shed some light on this.

 

[kwired]

That thought has crossed my mind a few times before also.

People can say that with the water piping you do not have potential heat producing materials inside like you do with a wiring method. Makes a little sense, but then why do we have all those sections in the code like article 240 and 310 where we are focusing on controlling the operating temperature of the wiring system? Why is a non metallic raceway going to get hot but a water pipe will not?True some worst case scenarios it does happen, and the water pipe contains self extinguishing media i guess. There are other plastics based items found in these areas sometimes though.

 

[hurk27]

For electrical PVC pipes it is because PVC can produce toxic smoke, I guess they think that plumbing PVC with water in it will put the fire out??? What about dry drain pipes?

 

[Cmdr_Suds]

You have different codes written by different people with different mindsets.
Water pipe has to NSF labeled and electrical conduit NFPA or someting like that. I figured there where chemical differences between the two. NSF being concerned with chemicals being leached into the water and the NFPA being concerned with the possiblity of fire spead and smoke production.

 

[iwire]

You have different codes written by different people with different mindsets.

I think that fact has the most to do with it.

 

[Gregg Harris]

For those inspectors and engineers out there, I would like to know why according to 300.22 in the NEC. Pvc conduit is not allowed in a plenum ceiling, however why then is plumbing pvc and cpvc allowed in the same space. Arnt they the same schedule 40 type just different color.. Maybe some of you have a co-worker who is a plumbing inspector that could shed some light on this.

2012 IMC 602.2.2 Materials within plenums Except as required by sections 602.2.1.1 through 602.2..1.5 materials within plenums shall be non combustible or shall be listed and labeled as having a flame spread index of not more than 25 and a smoked developed index of not more than 50 when tested in accordance with ASTM E 84 or UL 732. PVC and ABS does not meet the standard for plenum use, but water filled CPVC which is used for hot and cold potable water use does meet the 25/50 flame and smoke requirements for use in plenums.

 

[kwired]

You have different codes written by different people with different mindsets.
Water pipe has to NSF labeled and electrical conduit NFPA or someting like that. I figured there where chemical differences between the two. NSF being concerned with chemicals being leached into the water and the NFPA being concerned with the possiblity of fire spead and smoke production.

But all PVC made materials have similar toxins in the smoke when burned, true there may be some differences in composition but the base component is same and gives off nasty stuff when burned. All plastics are nasty when burned. People that die in structure fires, often die because of toxic gases given off by all the plastics that are burning before the fire actually gets them.

 

[copper chopper]

so only the pvc drain pipes would be illegal in a plenum ceiling??

 

[copper chopper]

well goerge turns out you were right, I asked the foreman for the plumbers today about this issue and they were busted buy the inspector 3 weeks ago but did not tell anybody. They have hired the same company that insulates all the duct work to go thru and wrap all the pvc drains and vents with a 3M product that protects the pipe in a fire. The inspector seems to be okay with that.

 

[RICK NAPIER]

I have dealt with that 3M wrap in plenums a number of times the inspector will need to check for proper overlap and strapping because it is missed a lot.