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make up air cooling

smklin Member Posts: 69
good day
I have a make up air system installed in a commercial kitchen . And have a steady supply of 50 to 60 degree water at 35 gpm can anyone tell me or direct me to a site that has info on how much capacity cooling or heating I have here ?



    EBEBRATT-Ed Member Posts: 9,024
    That may not be cool enough to get the job done. You need to contact an engineer who can design this system for you.

    You need a lot more information:

    Heat load of the kitchen and appliances to be offset
    Your location (to calculate OA temp & humidity load)
    CFM of air to be conditioned (air flow through the chilled water coil)

    Amount of exhaust air through the kitchen hood

    My best guess would be that with the water temperature you have the chilled water coil would have to be oversized to do the job. Normally chilled water would be in the 44 deg range + or-

    The water temp you have is very important a few degrees make a large difference.

    60 deg likely wont cut it. 50 may be workable
  • pecmsg
    pecmsg Member Posts: 1,994
    60° water and ?° air
  • smklin
    smklin Member Posts: 69
  • mikeg2015
    mikeg2015 Member Posts: 1,178
    On a 100F day you could cool 20,000 CFM by 25f (100% sensible) if you had a coil with a 10F aproach temp. With a 30F delta T with a 6 row coil you might be able to add 525,000 BTU to the water and raise it to 90F. You could then use that water to preheat DWH. Is the 35gpm a ground loop, or domestic water.

    However, the better way to do makeup air for a kitchen is a hood that supplies makeup air at the point its exhausted so you don’t need much conditioning of that air.

    60 would struggle however. Not sure you can get a coil with a 10F approach. IT would be cost prohibitively oversized. 55F is manageable but poor humidity removal (less of an issue in Montana). Need 50F to keep the coil cost effective.
  • smklin
    smklin Member Posts: 69
    edited March 2018
    the 35 gpm comes from a cistern that holds 60000 + gallons it is a open loop system . It gets pumped back into the same cistern it gets used for livestock. or ag spray water.or lawn irrigation.
  • Zman
    Zman Member Posts: 6,567
    Some more details are needed to even take a stab at this one. How many CFM is the hood exhausting is the first missing piece?

    The most common way to do this is to use the water in an evaporated cooler. Many commercial MUA units have evaporative coolers built in.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • smklin
    smklin Member Posts: 69
    The exchaust is 4000 cfm, the make up air unit is 3600 cfm there is a evaporated cooler in there it is almost worthless the only think it does very effective is add humidity to the kitchen. The make up air unit is running at 50 hz the exhaust fan is running at 60 hz we have to run it that way for the stale cooking air not to get pushed back into the rest of the dinning or working area.

  • Zman
    Zman Member Posts: 6,567
    edited March 2018
    In ballpark terms, assuming about 4,000' elevation, in order to cool the air 20 degrees you need about 72,000 BTU cooling (sensible).
    You are going to need to add something for latent (too much brain damage for a Saturday AM). Let's WAG it at 100,000 total.
    At your 35 GPM, you will have a water temp drop of 5.7 degrees.
    With 50 degree water, you should be able to get it done with reasonably sized coils. With 60 degree water, it is too close to call.
    I would suggest contacting a local HVAC rep and have them run the real numbers. Having an accurate supply water temp will be very important.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
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