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Plenum rated materials

Plenum rated materials

New postby bigdog on Wed Jul 28, 2021 3:07 pm

Jerry,

Do you know when the "only plenum rated materials inside of a plenum" rule went into effect?
I'm looking at a 1987 house that has the water heater installed inside the garage air handler plenum and of course its not been sealed back up.
The heater has been recently replaced but with the decal system here in PBC for such things the building department would never see it. I'm guessing since it was originally allowed they couldn't require moving it anyway.

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Re: Plenum rated materials

New postby Jerry Peck - Codeman on Wed Jul 28, 2021 7:17 pm

David, are you sure it is a plenum?

If so, then the water heater access could be an issue due to the plenum needing to be sealed up from the garage while also maintaining access to the water heater.

Sometimes things are just 'environmental air' closets and not a plenums. An example is a plenum closet in a hall way with a door (louvered or solid) with a water heater installed below the air handler unit. That would typically be considered environmental air and not a plenum ... unless the closet was sealed off from the hall way (solid door, with weather-stripping and a threshold which seals tight to the door, in which case it might be a plenum.

I don't have my codes with me, but I recall conversations about cable types suitable for use plenums back to around that time, however, development on those cable outer sheaths stopped (I don't recall why) and discussions started back up in the 2000s about plenum cables being rated. Thus the code may not have addressed that until the latter time frame, or even later.
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