Results 1 to 13 of 13
  1. #1
    I have a 1100 sp ft home, 2.5 ton Ducane Condensing unit/A Coil with furnace in attic.New parts are matched.
    The unit that I am working on ,1 mile from the beach,does not seem to cool well enough,or maybe the ambient temps may be too low ?

    Here's what I have (some plus or minus because of slight winds)

    Good air flow
    TXV
    OAT 73 , condenser outlet 85
    LLP 175, LLT 80.5,SLP 70, SLT 65.5

    12.5 subcool

    24 Superheat at condenser (imposible to access cassed evaporater)

    12 condenser dif
    16 drop across evaporater (measurment taken at return
    entrance and nearest register)

    Am I looking at sub par cooling because of low outside ambient tempatures ? Or should I be looking at something else.






  2. #2
    Forgot to mention that the operating amps are 8.4 and 7.7.

    on a unit that specifies 13.6 rated load amps.

  3. #3
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,845
    With a TXV I would not be that concerned with superheat "sure i will get some feedback over that" I would be more concerned with subcooling and it looks ok should not be stacking up with 12.5 subcool, what will the temps drop down to inside?
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  4. #4
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,845
    Originally posted by hotsummer101
    Forgot to mention that the operating amps are 8.4 and 7.7.

    on a unit that specifies 13.6 rated load amps.
    Thats probably normal because that is rated amps, not running amps.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  5. #5
    Join Date
    Oct 2003
    Posts
    2,866
    I would look at return air leaks in the attic. It all looks good accept for the supply and return delta t. If the return looked good i think i would add a littl freon and try to get a 19 or 20 delta T. You should be getting that easily.

    [Edited by appltech1 on 08-08-2005 at 09:31 PM]

  6. #6
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,845
    Originally posted by hotsummer101
    16 drop across evaporater (measurment taken at return
    entrance and nearest register)
    Try taking that temp. right at the return as close to the air handler as you can and right after the A coil at
    the plentum and see what you get.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  7. #7
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,907
    16 degree drop isn't the greatest. But before messing with the charge, make sure the blower is moving 1000 CFM. Need static pressure of system and look at blower chart and set blower speed properly.

  8. #8
    The outside temps are about 74 with 66 per cent humidity,sometimes higher, the inside temps with air on go down from 78 to 74 in one hour.

    because it's hard to measure in that tight attic I can only measure return air at filter and at register with shortest
    duct work.

    I know there is a closet with a 3 x 8 inch attic vent that needs to be closed off, this may have something to do with it.

    As far as the blower spped unfortunately I dont have the equipment to measure CFM and static preasure,so for now I can only assume it's OK at high speed, there is noticeably good air flow, always p[ossible it's too fast ?


  9. #9

    appltech1

    appltech1, you mentioned that I should be easily getting 19-20 Delat T, but since I can only measure at return filter (Ceiling) and nearest register how offset will my measurements be ? as opposed to measuring at the air handler.

  10. #10
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,845

    Re: appltech1

    Originally posted by hotsummer101
    I can only measure at return filter (Ceiling) and nearest register how offset will my measurements be ? as opposed to measuring at the air handler.
    A lot if you have any air leaks.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  11. #11
    Join Date
    Oct 2003
    Posts
    2,866

    Re: appltech1

    Originally posted by hotsummer101
    appltech1, you mentioned that I should be easily getting 19-20 Delat T, but since I can only measure at return filter (Ceiling) and nearest register how offset will my measurements be ? as opposed to measuring at the air handler.
    Reguardless of where i was taking my temps, on a 73 degree day, you shouldnt have to go any further than the return and any supply to take your measurements. The attic shouldn't be exceedly hot to cause heat penitration problems but you could have a hole in the return ductwork big enough to causea lower delta t. You do need to make an effort to examine the the a/h panels and return plenum.

  12. #12
    OK ' I'll have to make get the Delta T,
    if it's normal, let's say 18-20 degrees and I have no leaks,

    is there anything else I should be looking for ?

    For example, in this cooler region (near the beach) maybe I should have installed a diferent TXV , something more suitable for areas with low abient temps ?




  13. #13
    Join Date
    Oct 2003
    Posts
    2,866
    a 70 degree day is not going to stop the a/c from cooling. You already said you have a 16 delta T but you're a/c is not heavily burdened with hi OAT and the attic temp should not be a factor either because of the OAT. More thanlikely you need to add freon and get your super heat below 20.

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