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BTU question, air guys

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GW
GW Member Posts: 5,137
in THE MAIN WALL
Hello,

I'm looking at a commercial laundry room, I posted a note a week ago or so.

What kind of math do I use to figure how much heat of cool BTU I would need to offset 400 CFM outside air coming into a laundry room? We're in Mass. About zero* winter and 92* summer design temp.

Gary

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Gary Wilson
Wilson Services, Inc
Northampton, MA
gary@wilsonph.com

Comments

  • JimGPE_3
    JimGPE_3 Member Posts: 240


    Winter: CFM x 1.08 x (inside temp - outside temp) = BTUH needed.

    Summer: Figure about 220 CFM/ton for raw outside air flow.

    If you're actually going to do this, you need to know a lot more about the problem. The flue gasses will condense in the winter and drip onto your burner, so the heat exchanger and burner should be stainless.

    You can't do this with a common or guarden variety furnace and A-coil. You'll have LOTS of latent heat in the summer, so your cooling coil will need to be 6 rows or so, not the normal 3 rows for a furnace A-coil.

    Also, controls to keep the compressor from smacking on and off every few seconds can be tricky.

    Make sure you find someone who has done this successfully before. The trick is most people design systems for design conditions - the worst weather you'll experience. In this case, you can't stop there. You MUST consider shoulder months so you get it right the other 90% of the hours of the year.

    Or just buy a packaged unit made for 100% OA like an Aaon unit.

    Good luck!
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