Mechanical Room 1

[Fayaz810]

Hello experts,
I am working on a project where ................
Two air-handling units located in one mechanical room serve two separate fire-zone. Return air is ducted. Mechanical room has tight space.

If I delete return-air ductwork inside mechanical room and make it as common plenum with fire-dampers at the mechanical room wall openings, does it comply with the code?

One of my friend argued that it does not comply with the code but he could not give me clear explaination

Please advise

 

[ProcessHVAC]

Have you checked the code yourself? Which code?

 

[317069]

What code you are talking about, there are tons of codes.
What kind of building is it, residential, commercial ....etc.
You have all duct return installed and you are worry about a piece of duct between mechanical room wall and air handler.

 

[Fayaz810]

sorry, I forgot to mention,,,,,,,,,,,, We are using International Mechanical Code (IMC)

 

[urgross]

The answer is no, your friend is correct. Plenum is limited to one fire zone. Refer to 602.1.

 

[317069]

What about two commercial suites separated by a fire separation served by on air handler

 

[urgross]

You can have multiple zones, multiple floors and multiple occupancies off the same air handler, and even combine NFPA 90A and NFPA 92 on the same AHU for all those floors and zones. Looks really messy on a pneumatic control system.