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  1. #1
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,403

    Exhaust and possibly MUA for a small room?

    At the local votech they are doing some changing. They are moving 3-4 blueprint plotters into this room. They also have one of them plastic prototype machines (not 100% sure how it works, but it looks cool!).

    Anyway, this room is 20'x20', about 8.5' tall. Obviously the stink will be great in there, and they are worried about that. They don't know what they want, they just want something, and cheap. My 1st thing to say was talk to an engineer about this, as they can figure everything up "properly (hopefully)", and sign off on it to eliminate any problems down the road. They don't want to... that's our job I guess.

    I'm not real sure what to do here.... I would guess that 300-500 CFM might be enough, but likely on the small side. Not to mention there's no real good place for make up air. The 2 walls into the hallway are fire rated, so a fire damper would be required (or a fire rated grill?). The other 2 walls are into other rooms, and we can't transfer there because they aren't near big enough either.

    Could bring it in from the roof (where the exhaust is going out), but then we'd have to heat it too, well to do it right anyway.

    I kinda thought of a HRV, but there's no possible place to put the cond drain into for at least 50' or more (plus numerous fire walls).

    Every good option I can think of to do this right will involve at least a couple grand, but likely much more than that... and I have a good feeling they'll throw our bid out (not always a bad thing).

    So, what would you guys do?
    "If you call that hard work, a koala’s life would look heroic."

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  2. #2
    Join Date
    Dec 2001
    Location
    Southern Tier, NY
    Posts
    6,066
    they're prolly lookin' at 6k$

    rooftop, w/ power exh,
    duct
    gas line
    roofing
    curb
    electric
    etc

    that ..

    or open a window

  3. #3
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,403
    Can't seem them going with a RTU (aside from cost). The whole school is full of VAV's and boilers (and chillers I assume). The building is controlled downtown, so a RTU would be something else for them to control... only they wouldn't know when to control it, and I'm sure wouldn't leave that up to the teachers lol.

    Seems like a no win situation really.
    "If you call that hard work, a koala’s life would look heroic."

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  4. #4
    Join Date
    Apr 2002
    Posts
    11,808
    There is no way of doing this cheap. I wouls says slims estimate is a little slim
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

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  5. #5
    Join Date
    Dec 2003
    Location
    Northern VA
    Posts
    619

    Dvs

    I think the hrv with a cond pump with copper tube disch. thru the firewalls and the seperate mua/exh ducting is the right direction if the RTU is out of the question.
    The control could be locally with a CO2 sensor in the space with a lockbox.
    A demand ventilation system.
    "Iron sharpeneth iron..."

  6. #6
    Join Date
    May 2004
    Location
    Illinois
    Posts
    2,843
    Quote Originally Posted by amickracing
    The whole school is full of VAV's and boilers (and chillers I assume).
    If you have hot and chilled water available, it shouldn't be that big a deal to rig up a little 2T fan coil as a makeup air unit. Interlock it with the exhaust fan and stick a 2-position damper on the OA louver.

    You might also want to look at how the return/relief air works in there. You might be able to divert a little relief air through that room for pretty cheap.
    "If I had my life to live over again, I'd be a KA." - Albert Einstein

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  7. #7
    Join Date
    Dec 2001
    Location
    Southern Tier, NY
    Posts
    6,066
    Quote Originally Posted by Carnak View Post
    There is no way of doing this cheap. I wouls says slims estimate is a little slim

    Maaaaybe ....

    i was figgerin' a 3 ton electric heat ....

  8. #8
    Join Date
    Dec 2001
    Location
    Southern Tier, NY
    Posts
    6,066
    Quote Originally Posted by slimwoodie View Post
    Maaaaybe ....

    i was figgerin' a 3 ton electric heat ....
    Whoop's ... I did say .... Gas Line .....

    didn't I ....

  9. #9

    MAU / EF problem

    You mention the school has a (or a few) variable volume systems running through it. That may be your only option. The plotters don't produce much heat load, however the prototype machine may, so heat load calcs should probably be done to satisfy that equipment. I think 600 to 800 CFM should be plenty sufficient for the space. You should consider tapping into the existing variable volume system and running a CONSTANT VOLUME box to the space. You need to grab exhaust from somewhere though and you don't mention that situation. If there is a system that can be increased to handle upwards of 800 CFM then you may be in luck. However, it may be more beneficial to install a dedicated exhaust system for the space. Also, have the box calibrated to maintain the supply total but have it control to the space pressure. I would think you may want that room to be slightly negative (-0.01 to -0.05"wg) to the adjacent space(s) or better yet a corridor. This allows the room to be properly ventilated through the BMS system.

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