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  1. #1
    Join Date
    Apr 2011
    Location
    Minneapolis, MN
    Posts
    1

    Direct Fire Makeup Air units and temp rise

    Hi and thanks for looking!

    I have run into some confusion regarding make up air temp rise. When a unit data tag or documentation lists a given temp rise at "design temp" (not posted), should I presume they mean my regional winter design temp such as manual j temp? Also, more importantly, is the listed temp rise linear to the outdoor air temp?

    Example: If the maximum listed temp rise is 100 deg f at 29 deg f (max discharge would equal 129) would the max temp rise at 0 degrees be 100F ?

    If not is there a way to calculate what my temp rise should be at a given outdoor air temp?

    Assume a constant volume system and single speed fan...

    Thanks for your inputs!

  2. #2
    Join Date
    Oct 2004
    Location
    toledo, ohio
    Posts
    63
    Temp rise does not care what the od temp is... You are correct that if 0 then 100 would be correct.. Certain mfgs will have you direct more or less air towards the high limit so as to trick the unit... Like Cambridge units do.. So as long as you are under your high limit setting you are within operating spec.

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