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  1. #1
    775 ft2 house with a properly sized/matched 2 ton Goodman unit in Houston. Adequate ventillation of the attic space above the living space, 5 inches of R19 blow-in insulation. Attic well sealed from living space. Northwest side facing windows all double insulated and tinted. Starting around noon and continuing until ~ 9 pm, unit will run constantly and the house temp doesn't get below 82.

    I had a tech come out who checked the pressures, advises it's properly charged and running correctly, coils (both condensing outside and evap inside) clean. He did notice a kind of squealing noise on the high pressure tubing inside the house just before the evap coil. He told me that it was the result of incomplete condensing (the squealing noise was gas/liquid moving through the line that only liquid should be moving through), and that probably my outside condensing unit is too hot to do it's job. Problem is, that squealing noise occurs all the time (even when it's early morning and cool all around) so I don't think it's simply the ambient temp around the condensing unit.

    So I'm stumped, as is the tech. Any suggestions?

  2. #2
    Join Date
    Apr 2003
    Location
    Eugene, Oregon
    Posts
    1,209
    Your first sentance say's it all.
    Proud supporter of Springfield Millers and Oregon Ducks.

  3. #3
    could you elaborate?

  4. #4
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by earthcondition
    775 ft2 house with a properly sized/matched 2 ton Goodman unit in Houston.
    How do you know it is properly sized?

  5. #5
    Join Date
    Apr 2005
    Location
    Inland Empire,CA
    Posts
    56
    need pressure readings, could be non condensibles or compressor not to sure without more info.
    wow a 775 sqft house in Houston with properly sized 2 tons of cooling. some in here would think thats too much

  6. #6
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by earthcondition
    Any suggestions?
    Measure the temperatures at your return and supply registers and (if you can get to it) at the return and supply plenums at the air handler, and post them here. If you have the condenser pressures from the tech's visit post them too, along with the outside temperature.

  7. #7
    I wrote 'properly sized' as that's what my tech told me...his rule of thumb for our exceedingly hot/humid climate is 400 ft2/ton.

    Even if the system were oversized, would that explain the problem of the house not cooling? The unit does not cycle off at all from noon to 9pm, and the interior climate of the house does not seem to have a humidity problem.

    If there is a problem with non-condensibles, how might one test for that? What is the corrective action? Evacuate and recharge to ensure the system is totally clean?

  8. #8
    thanks travisfl, I'll collect those readings and post asap.

  9. #9
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by earthcondition
    I wrote 'properly sized' as that's what my tech told me...his rule of thumb for our exceedingly hot/humid climate is 400 ft2/ton.
    Your tech could have done a more professional job on sizing.

    http://hem.dis.anl.gov/eehem/95/950509.html

    Having said that you still have a problem that needs resolution. Let's press on with the diagnostics and perhaps someone of us on the forum will be able to help you.

  10. #10
    Join Date
    Sep 2002
    Posts
    606
    we need pressure readings . Id say the unit is either undercharged or the ductsystem is inadequate for air flow.

  11. #11
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,389
    There's your first mistake, listening to a tech's rule of thumb. But still 2 tons for small space with good insulation doesn't sound bad even for Houston.

    Where's the ducts? In the attic? If so, are they picking up attic heat?

    My house is 950 sq ft with 2 tons, about 1/2 ton oversized per the manual J but since I like it cold I stayed that. Yesterday we were just like Houston with temps in the 90s and dewpoints mid 70s. When I got home it was 70 just like it should be, humidity lower 50s. Stat called to lower to 68 for bedtime but for 2 hours temp didn't budge

    I only get 1-2 degrees of attic heat in the return, ducts in a heavily insulated crawl so don't pick up heat there. In humid weather, I run about a 17 degree drop over coil. In dry weather it runs around 20. I have a dual display thermometer watching the supply & return!

  12. #12
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by BaldLoonie
    I have a dual display thermometer watching the supply & return!
    Me too, Bald One...in my case I'm using a wireless thermometer with a three channel display. The last channel reads the attic temperature. This summer's project is to add a sensor for the pool....

  13. #13

    Mine is like this too!

    I have posted before and this has been going on two summers in a row for me! I have a 1,970 sq. ft. home and a 3-ton rheem unit. My unit works fine up til about 90 degrees then when it gets above 90 the temp. in my house rises 4 or 5 degrees above my setpoint. I have had several techs come out and some just tried to sell me a new unit and mine is only 4 years old and still under warranty. My coils are clean, pressures are good, not overcharged, filter is clean, etc. The last guy to come over seem to know more than the rest and said it could be an air flow problem. he did some work around the airhandler and it seem to do fine unitil today when temps got up to 93-95 and with my ceilings fans on the temp. rose above setpoint(which was 72) to 75. The first two years I lived here it didnt matter how hot it got, if I had it set at 72 it would be on 72. I am at wits end. I have two gable vents, two turbine vents and pancake vents in my attic that have exhaust fans if I got them hooked up would they make a significant differance?

    thanks

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