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  1. #27
    OK, this may be the final chapter on this saga...

    The 2-ton vs. 3-ton issue was freaking me out. So I spent $50 on HVAC-Calc Residential to run a Manual J on my own. Guess what? No matter how pessimistic I am with entering the data, it tells me a 2-ton cooling system is plenty adequate, as is 40,000 BTU heating. It took me all of 30 minutes to run those numbers. Why the heck don't the estimators use something like that when they visit the house? That's baffling to me.

    If I'm to believe the Manual J, the original system was in fact sized correctly from Day 1, but if that's the case then the heat pump probably never worked right for whatever reason.

    So, I cancelled the new furnace and told them to swap out the 3-ton system for 2-ton. They swapped the heat pump, but left the coil a 3-ton because it's too much trouble to change it out again. Does that seem OK? The system is running now and it seems to be performing very well in cooling mode, on a pretty warm day here. It will get a workout this weekend which is supposed to be very warm.

    This was a learning experience for me. EEK!

  2. #28
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by typical homeowner
    Why the heck don't the estimators use something like that when they visit the house?
    THAT is the question I most often ask myself. It is baffling to me, too.

    Good job on taking the sizing into your own hands. Be sure to share the results with your contractor....maybe he'll get a hint and see the value of doing more calculating and less guessing on future installations.

    If you can provide the model numbers of the 3 ton coil (Goodman?) and the 2 ton condenser, we can tell you if they are an approved match, or not.

    [Edited by travisfl on 07-15-2005 at 06:12 PM]

  3. #29
    Both Goodman

    Heat pump is CPLT24-1B
    Indoor coil is CAPX036B2A

    The installer assured me these are OK together. But hey, I've learned not to trust what they tell me, haven't I?

  4. #30
    Join Date
    Jan 2005
    Posts
    340
    I don't see this combination listed in ARI PrimeNet, but then I'm not a Goodman expert. PrimeNet does list coil sizes up to 3.5T paired with the 2.0T HP, just not the coil you listed.

    Maybe one of the other guys can advise if this is a 'matched' set.

  5. #31
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    i am glad you got your cooling back. not sure if the coil is ok. good luck with your system and hope you are done with all your problems. good luck

  6. #32
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,933
    I'm really sorry I am late looking at this thread. I was actually asked to look at it.

    It seems that most advice given here was good advice that was not listened to till the end. The load calc should have been done from the beginning but no matter what other factors, this is only a 2 ton distribution system and anything over that capacity is going to have issues.

    Heat mode should never have been tested other then to make certain the reversing valve shifted. Between the high ambient and the low airflow it's a wonder the compressor didn't shut down on thermal overload.

    There is no reason that the CAPX36 shouldn't be fine with that CPLT24. I will check to see if Goodman rated this combo, but the indoor coil has a TXV and the heat pump is a 13 SEER so the larger indoor coil is in order.

    Why the company that installed the Goodman heat pump would consider installing a Lennox furnace instead of a Goodman furnace has me baffled. With all of the rhetoric about Goodman equipment there is no doubt that the Goodman variable speed condensing furnaces are by far one of the best furnaces on the market today. Variable speed would have boosted the SEER rating of the cooling to 14 SEER by the way.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  7. #33
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    So it's cooling,how's the indoor humidity?

  8. #34
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,933
    Indoor humidity is definitely something to keep an eye on. With the TXV the system should have decent control over humidity as long as the furnace blower is operating at 800 cfm of air or less (preferable for dehumidification).

    That CAPX36 coil is not specifically rated as an ARI rated match for that heat pump, but again, will actually do a bit better then the CA*F30 and CA*F42 coils that are rated for that heat pump. The difference is the TXV in the CAPX36 coil, which is better for controlling coil temperature for better dehumidification.

    For energy efficient built houses it is best to immediately get rid of excess moisture such as cooking moisture and shower moisture by using exhaust fans, but it is also best to keep exhaust fan usage to an absolute minimum unless your home has an air-to-air heat exchange system for exhausting high humidity conditions.

    [Edited by RoBoTeq on 07-16-2005 at 06:01 PM]
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  9. #35
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    How about the dischagre air temperature in heating,with the larger coil?

    I know we sold some matchs like that in the 80's to get the desired SEER,and the complaints were numerous.

  10. #36
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,933
    The larger coil does not change the overall amount of heat from condensing refrigerant. It is true that the coil will not be as hot per square inch of coil surface, but with the overall temperature from the increased coil surface area, the amount of heat in the airstream is the same.

    What happens in most cases is that the larger coil used is in an air handler designed for a larger capacity system. In this case there is more air flow then is proper for the application. This additional airflow decreases the leaving air temperature of the system supply plenum.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  11. #37
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Even with the correct air flow ,we had complaints of cool discharge temps.

    Those same homes have better match systems today and no complaints.


    Agreed in regard to total heat,and they could always maintain the indoor design,just cool blow.

  12. #38
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,933
    In this particular case, an even larger indoor coil is rated with the heat pump. Again, the primary difference in the coils that are rated and the one that is installed is the TXV.

    In any heat pump system, if there is a complaint of too cool of air leaving temperature, a reduction in blower speed will resolve the issue.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  13. #39
    Sunday is supposed to be 90+ here so the system will get a workout. It ran all afternoon Friday. It was mid-80s outside, system had no problem maintaining low 70s inside. I have no way to measure humidity, but subjectively it seemed OK yesterday and there was a steady [small] stream of water from the condensation drain so it's doing something.

    A couple bonuses: This 2-ton 13-SEER Goodman is *very* quiet. And they installed a new Honeywell VisionPro 8320 thermostat with outside heat sensor as compensation for my trouble.

    Thanks to everyone for your assistance. This has been an eye-opening learning experience for me.

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