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  1. #1
    Join Date
    Feb 2008
    Posts
    16

    Question Need make up air - AC help

    I have a commercial building it has 2- 10 ton roof top unit. There is a make up air unit in the kitchen and two exhaust fans in the kitchen. The make up air unit has fail the motor is burnt out. Here is my situation and my thought,with the make up air unit not working and two exhaust fans pulling out three thousand CMF give or take, is 7 tons of cooling (3000cfm) now going out my exhaust fans? the kitchen and the dining area are not seperated by any type of doors its just all open. I just cant keep this building cool. Am I even close here I am just driving myself crazy trying to keep a customer happy

  2. #2
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,122
    7.5 tons to be more exact by general rull of thumb, and the answer is that yes the cooling is going out with the make up air on or off.
    Now, relax a little. It is not the cooling that is probably going out. You are removing the heat from the kitchen(I assume this is in a kitchen area of a restaurant). Heat rises, cool air falls. You are taking the heat off of the stoves so that you don't have that load on the AC units. As for the makeup air unit, unless some sort of damper has closed, you still have fresh air coming in the through the unit, although it is less. Where you are loosing cooling is in the areas of the building that the exhaust fans are pulling from trying to make up for the makeup unit not running. this should be an easy fix, so don't sweat it. Just do it. As for trying to keep the owner happy, that usually is in vein.

  3. #3
    Join Date
    May 2007
    Location
    maryland, baltimore
    Posts
    135
    You really need to fix the make up air unit as you are pulling air from unwanted areas through the space. Bathroom exhuast fans are fighting to pull foul air out while the kitchen is pulling it back in, also the waste traps/vents will dry out and bring more unpleasent odors into your space. Your a/c is supplying some of the exhausted air, but that depends on how much outside air is available to the units. Had a new resturaunt call with a foul odor problem, someone else was in charge of exhuast/ make up air start up. Air balancing completely over looked it also, Make up fan was turning backwards and sewer gas was migrating into hallways. Mexican resturaunt, you know the rest. The ovens and fryers will also be directly affected. Get it repaired.

  4. #4
    Join Date
    Jun 2004
    Location
    St Paul, minnesota
    Posts
    1,015
    fix the MUA unit

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