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  1. #1
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    Mar 2018
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    Mechanical Room as Return Air Plenums

    Hello there!

    Hope everybody is doing fine.

    What are your thoughts about using mechanical room as return air plenums?

    Advantages? Disadvantages? Personal experiences? Tips?

    Thanks and have a nice day yall.

  2. #2
    Join Date
    Jul 2006
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    Chattanooga, TN
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    NO.

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  4. #3
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    Oct 2015
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    No and against code
    There is only one truly right way to do something, but there are thousands of wrong ways to varying degrees to do it.
    So the question is: If you don't do it right, then how wrong is it going to be???

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  6. #4
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    Nov 2006
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    Athens, Ohio
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    No! And a potential danger to equipment and building occupants!
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  7. #5
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    Mar 2015
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    I Agree with the "No"s, & I'm wondering why in the World one would want to do this.

  8. #6
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    Jan 2004
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    I saw this done at an Elementary school once with 2 Trane vertical self contains, and the reliefs weren't piped outside, idiots.
    Federal Reserve, stealing your kids futures since 1913

    UA290

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  10. #7
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    Mar 2018
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    Thread Starter
    I'm from Brazil, local code allows for it and i've seen many. (i'm not saying it's right or wrong)

    Here's an example of this application:

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    It's an air-cooled self-contained unit.

    Both condenser intake and relief are ducted outside.

    Mechanical room is next to the conditioned room.

    Return air comes through the grille/register and goes directly into the equipment room. There is not duct connecting return air to the units.

    There is also an outdoor air intake grille/register.

    Name:  trane.png
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    Above is a printscreen from Trane's product catalog, where this procedure is considered.

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  12. #8
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    kansas
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    Quote Originally Posted by kdean1 View Post
    No! And a potential danger to equipment and building occupants!
    How is it a danger to equipment? Many new construction uses a common return back to the mechanical room where it is mixed with outside air in where the mechanical becomes a mixing box?
    Honeywell you can buy better but you cant pay more

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  13. #9
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    Aug 2016
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    San Diego
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    I don't know why you'd do it, but I don't know why it would damage equipment. Granted I've only seen it done with some smaller units in a really old building. Albeit it wasn't in a mechanical room but just to the space above the t grid.

  14. #10
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    Aug 2006
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    We spec. that design. The Mechanical rooms are much cleaner, the air is filtered through cheap PSF-1 filter material. Also we have less insect problems in these rooms, with the added benefit of the rooms being heated and cooled. The rooms have reliefs in them. As long as its not a Boiler Room, which would be illegal, I don't see what the problem would be.
    I only have to make it work till I retire.

  15. #11
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    Mar 2018
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    Thread Starter
    The only equipment in the room is the cooling equipment

  16. #12
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    Mar 2015
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    Interesting.

    But I can see where concerns for Fire Spread,Chemical contamination,& more do arise.

    And that is why, "Return Air" from a Mechanical, Utility, &/or, Bathrooms,as well as Kitchens is prohibited.

  17. #13
    Join Date
    Aug 2006
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    There are duct Smoke detectors on both the return and supplies, there are Smoke dampers on the units. Smoke Detectors in the Mechanical Rooms. We are limited to what we can use for cleaning in the Mechanical Rooms, also when we do cleaning with chemicals, Emails are sent out to the building occupants, along with notices posted in the building. Often cleaning is done after hours or on the weekends. BTW this is not a Plenum Mechanical Room, just Relief air from the building. BTW we do have one old Mechanical Room that is the return, but the relief isn't in that room. Outside fresh air is ducted to that unit.

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