Multi-Family closets used as plenums for split systems

[nuuvox000]

I'm a little confused by the IMC as far as a split fan coil in the mechanical closets of apartments. The code clearly allows the closet to be used as a return air plenum but then all of the materials need to be plenum rated? I don't believe all of the components in the fan coil itself are plenum rated. Plus, there is typically a water heater in the closet as well which I'm sure has components that aren't plenum rated. When I ask manufacturers about this, they all give me a big "huh?" like they've never heard of something like this before but they all build equipment with "free-air" returns and sell thousands of these every year. Has anyone run into this issue before? Am I missing something simple in the IMC that allows the closet to be used as a plenum even though the unit itself is not plenum rated?

 

[trashcanman]

No way I would sign off on such a design. You would be setting yourself up for a huge lawsuit if someone was injured or killed in a fire in such a plenum. Regardless of what the industry says, you had better protect yourself and license by strictly following the adopted code.

 

[HVAC-Novice]

Other codes, like IBC, require plenum rating. You have to meet all applicable codes.

 

[dbill74]

Simple solution is to nix the plenum.
Just a little duct connected to a grille would solve the problem.
Have to go thru the wall with the closet door? Use a half door and locate the grille below the door.