Page 1 of 2 12 LastLast
Results 1 to 13 of 15
  1. #1
    Join Date
    Aug 2002
    Posts
    490
    split air cooled comfortmaker 3 ton
    suction pressure 80
    head pressure high side 215

    suction line temp. 62f
    high line temp 95f

    outside air temp going into condenser 76f

    note long line set evaporater and blower in attick above second foor used for second floor only.

    customers complaint not cooling good

    took air temp out of upstairs register 63f

    took air temp going back in return upstairs 73f


  2. #2
    Join Date
    Feb 2004
    Location
    southern illinois
    Posts
    5,522
    overcharge?..

  3. #3
    Join Date
    Apr 2003
    Location
    the Great Pacific Northwest
    Posts
    607
    suction pressure 80=48 degree f,suction line temp. 62f=14 degree f superheat
    high line temp 95 degree f, head pressure high side 215=107 degree f=12degree subcooling
    Not overcharged
    107 degree saturated condensing temp.outside air temp going into condenser 76f=31 degree f delta t
    High for newer (10 seer) about normal for older equiptment
    coil probabaly needs cleaned, charge may be a little low.
    10 degree f delta t at registers? need to check at air handler you may have a loose/leaky return system.

    note long line set evaporater and blower in attick above second foor used for second floor only.

    liquid line my be under sized and flashing in hot attic , may need to be up sized and/or insulated.

    Last thoughts: you probably have a combination of problems here that have accumulated to cause a loss of performance the last thing could be a weak compressor, the key as always is to look at the complete system.
    Let us know what you find out.

  4. #4
    Join Date
    Feb 2004
    Location
    southern illinois
    Posts
    5,522
    yeah dump the juice to it and see where your superheat goes....i would think overcharge or low airflow is what i would be looking for...i would want my superheat a little more than what you got now...

  5. #5
    Join Date
    Jun 2001
    Posts
    3,910
    For an older system pressures would be ok.

    I was thinking leaky return also. Take temp measurements at return inlet at air handler and return grille to exclude return leaks.

  6. #6
    Join Date
    Aug 2003
    Location
    Central Kentucky
    Posts
    6,247
    Originally posted by hvac-tech-lane
    suction pressure 80=48 degree f,suction line temp. 62f=14 degree f superheat
    high line temp 95 degree f, head pressure high side 215=107 degree f=12degree subcooling
    Not overcharged

    10 degree f delta t at registers? need to check at air handler you may have a loose/leaky return system.
    I think lane may be on to your problem here.
    Your problem may not be with the equipment just the ductwork it is attached to.
    The duct system may not have adequate insulation & you may be gaining heat through it from the attic.
    The other culprit as lane mentioned is duct leakage.
    Take some temperature measurements at the equipment to see how much gain you are getting through the ductwork.
    Try this formula when you take those measurements:

    supply temperature at the farthest grille minus supply temperature at the evaporator divided by the delta T through the equipment= the % of BTU gain through the ductwork.
    Example:
    temp at farthest grille- 63 degrees
    temp at evaporator- 53 degrees
    delta T at equipment- 20 degrees

    63-53 = 10 degrees divided by 20 degrees= 50% loss in capacity through the ductwork.
    Not saying this is your problem but it will give you somewhere to look.
    Try checking the static pressure & verifying you have proper airflow across the evaporator in addition to this.

    Good Luck
    Have you set up a Google alert for Carbon Monoxide yet?
    Click here to find out how.

  7. #7
    Join Date
    Feb 2004
    Location
    southern illinois
    Posts
    5,522
    leaky return it could be....80SP would be high pressure for 73 indoor...

  8. #8
    Join Date
    Apr 2003
    Location
    the Great Pacific Northwest
    Posts
    607
    Originally posted by mo-flo
    yeah dump the juice to it and see where your superheat goes....i would think overcharge or low airflow is what i would be looking for...i would want my superheat a little more than what you got now...
    With respect sir at only 12 degrees subcooling how would you suspect overcharge? And at 10 degree delta across evap with 80 psi suction and 14 degrees superheat how would you figure low air flow?

  9. #9
    Join Date
    Apr 2003
    Location
    the Great Pacific Northwest
    Posts
    607
    Duke, what type of metering device? also how much diference in elevation is there between where you are taking your readings and the metering device, this will affect your subcooling thus if you have a solid column of liquid at the metering device.

    [Edited by hvac-tech-lane on 06-18-2005 at 05:03 PM]

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,727
    Sure sounds like its sucking attic air, with that 80 psi suction pressure.

    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  11. #11
    Join Date
    Aug 2002
    Posts
    490
    THE METERING DEVICE IS A CAP TUBE
    the line set up around 25 feet to the attic another 17 feet to the evap total 40feet
    also has electronic air cleaner pulled it look clean

    Now when u walk in the front door stairs are on the left open ceiling is like 25 feet high with skylights in that part of the house.
    One big room in front of the house, at the top of the stairs there is like 28 feet of railing u can look down from up there are 4 rooms up there.

    also three registers off that balcony and two small returns
    They had the bedroom door closed to the master bedroom with the t-stat took temp off that return and register also ones off the balcony.
    note bedroom was cool

    I thought maybe the air coditioning for the down stairs may not be cooling enough and maybe upstairs was working harder for that.
    so I took reading off down stairs unit too.
    used to cool down stairs
    suction pressere 65
    head pressure high side 185
    outside temp air ging in condenser 76f
    suction line temp 59f
    high line temp 92f
    small refrigerant under charge
    also registers down stairs 61f
    return grill 74f
    did not check out blower downstairs homeowner said they had a electronic air cleaner there also they clean once a year told em to do it every six months.
    anyway i was on this service call for the upstairs unit just thought i would go the etra mile.
    there initail complaint upstairs not cooling
    cold it be the dirty condenser for up stairs and the little bit of the low charge down stairs unit be the problem.
    well will take all opinions thank you

  12. #12
    Join Date
    Aug 2002
    Posts
    490
    oh Duct work is all good went all through attick.
    no leaks tight best i seen in a while

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,727
    40' isn't that long.

    First clean the condenser coil.

    Then run it again, and when the system stabilizes recheck the readings.

    If you still have the same basic readings, then shut the indoor fan down and watch the frost lines.
    You could have a slight restriction in one of the caps, and someone else may have added gas last year or earlier to get it to cool again.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event