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50-ton AC Rooftop Unit Feasibility Question

Looking at a 50 ton air conditioner on roof, unused at the moment. Customer needs about 4-5 tons of cooling in their lab for year round cooling. Contractor proposed to duct the unit to the lab and claims they can make adjustments / set it up to work for load required. Does this sound feasible?

Comments

  • Harvey RamerHarvey Ramer Member Posts: 2,214
    Not even a little bit.
    Using a 50 Ton AC unit for a 5 Ton load is a felony.
    Ramer Mechanical
    ramermechanical.com
    To learn more about this professional, click here to visit their ad in Find A Contractor.
    ZmanIronman
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 6,945
    As @Harvey Ramer pointed out...REDICULOUS. Don't even try it. This would be the worst energy pig on the planet.

    Just for fun how many compressors does it have? 2 @25 ton, [email protected] tons, 4 @12 tons???

    Even if it was a "modern roof top" with 5 10 ton scroll compressors it wouldn't work

    TERRY1Ironman
  • TERRY1TERRY1 Member Posts: 9
    Thank you for the feedback.
  • JUGHNEJUGHNE Member Posts: 6,796
    The few rooftops I have seen were all oversized and under ducted.

    My wife's medical lab in a small hospital was short changed on cooling thru 2 or 3 highly engineered remodels. They were using spot coolers.
    As instruments were approaching overheating and auto shutdown. The threat was that no instruments.....no lab.....and Hospital not being allow to accept patients. This is the bell that was rung to get something done.

    I had her go to each and every instrument, including all the UPS battery chargers and make a list of power consumption. This was converted to BTUH gain and presented to the HVAC contractor. He was actually wise enough to say he will put AC in but we have to tell him the heat gain. (Conflict of interest for me to pursue the job.....actually if it was short on cooling with 4 mid age women working there.........better him than me ;) .) ......but the heat gain was actually my calculation).

    They ended up with two 2 ton higher end minisplits HPs with ceiling cassettes....little wall room available. Hardwired T-stats for each unit. The building chiller/HW system provides enough heating/cooling for just the building area of the lab. Occasionally the heat pump portion is used.

    Again the engineers had figured the heat gain of building only and either ignored or were unaware of the instrument (computer) load of a modern Med Lab.

    So now all 4 women are cooled perhaps enough, also they are required to wear lab jackets.
    4 Mommas' happy.....many others happy. B)
  • IronmanIronman Member Posts: 5,570
    TERRY1 said:

    Looking at a 50 ton air conditioner on roof, unused at the moment. Customer needs about 4-5 tons of cooling in their lab for year round cooling. Contractor proposed to duct the unit to the lab and claims they can make adjustments / set it up to work for load required. Does this sound feasible?


    Anyone that would tell that big of a lie would steal anything they could get their hands on!
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • JUGHNEJUGHNE Member Posts: 6,796
    Has a accurate heat gain been done for that lab?
    The one I mentioned was for a pretty small room that had surprising heat gain need about 4 tons.
    You might need more that the 4-5 tons mentioned, but no way would the 50 even ever be good.
    The minisplits would modulate the compressor speed as needed.
    FWIW
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