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  1. #1

    Question

    Not an HVAC professional, but handle facilities issues for a 2-story 8K sf brick building with black shingle roof. One section is on top floor and gets southern and western exposure. Today is in upper 90's and the Trane XE 78 unit supplying that section is putting out 76 degree air at a ceiling discharge vent. Room temperature at wall thermostat is 78 degrees. Stat is set on 75, but unit has not reached it in the heat of the day according to occupants. Inside humidity is about 60%, not sure about outside, but in this heat in NC, the heat index is probably in the low 100's. Unit was serviced about 3 weeks ago on a six month PM and the condenser coil cleaned and filter was changed. Getting occupant complaint that they are warm, but I think the A/C is doing all it can do. Should I expect more? Is it time to call the HVAC tech back in to look for other problems?

  2. #2
    Join Date
    Mar 2004
    Location
    SE Michigan
    Posts
    17,851
    May be undersized for the load. Need a load calc. done to determin proper size. What is the return temp and supply temp? what are the operating pressures? model + serial? superheat/subcooling?
    "Politicians are the lowest form of life on Earth. Liberal Democrats are the lowest form of politician"

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  3. #3
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    3,255
    Has it done this beofre when hot? If NC is like Va, the a/c is sized to maintain only up to 95, so if the outdoor temp gets higher, the air temp inside will rise ,too.
    Col 3:23


    questions asked, answers received, ignorance abated

  4. #4
    Join Date
    Oct 2003
    Location
    Florida's space coast
    Posts
    2,538
    Under the conditions you described, I'd feel fairly safe saying that system is pretty well maxed out.
    We've been doing so much,for so long,with so little, that now we can do almost anything, with nothing at all.

  5. #5
    Senior Tech Guest
    At 100 degrees outside the best you can hope for is 80 degrees inside. (20 degrees difference) anything beyond that is purely bonus points. If they think they're hot tell them to go outside for 15 minutes and go back in...they'lll notice a big difference.

  6. #6
    If it is maxed out, you will need to discuss both short term as well as long term plans for a solution.

    Long term may be adding more cooling or even replacing exhisting system with new better & bigger system.

    Short term plan may include adding auxillary cooling by one of those rent a BTU places.

  7. #7
    Thanks for your inputs. Appears from the answers that 1) the unit may be maxed out, and 2) further investigative work by an HVAC Pro is warranted.

  8. #8
    Join Date
    Oct 2003
    Posts
    566
    Originally posted by senior tech
    If they think they're hot tell them to go outside for 15 minutes and go back in...they'lll notice a big difference.
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  9. #9
    Join Date
    Mar 2003
    Location
    Cincinnati
    Posts
    7,977
    When do you start up? You're not trying to perform start-up 1/2 hour prior to the building being open are you?

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