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  1. #1

    Confused New Trane system not working PLEASE HELP!!!!

    Please please help. I had an old 3 ton heat pump that was not cooling all that well (in certain parts of the house, away from the air handler) but did cool the other half of the house just fine and most important: it always kept the humidity level in the house between 45 and 50%, no matter how hot and humid it was outside.

    I did all my research and hired what I thought was the best contractor in my area to install new Trane system (which I heard they changed the systems this year), which I have always trusted. The company recommended a 4 ton system. FWIW I have a 1950s ranch that is about 2000 square feet and I live in Florida. Note: The house is very tight despite its age, etc. Well, the new system is shooting massive amounts of cold air through the house (compared to old system) but the humidity level will not decrease below 58%. I have to keep the thermostat at 73 in order to keep the humidity at 58%. Which is freezing. I used to be able to have the thermostat at 77 and the humidity was in the high 40s. Because the house keeps the temperature inside well, the new AC does not turn on unless I turn the temperature down low. If and when it does turn on it is for a short period of time, less than 10 minutes (then again temp outside is low 70s). Btw, fan speed was lowered by the technician and situation is the same. It's just cold and clammy in my house.

    Please advise!!!!

  2. #2
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,051
    You aren't running fan constant are you?

    They made problem worse by putting a 4ton . Was this their"fix" for problem area?

    Did they add some vents and return to handle the extra ton they added?

    With the low outdoor temps yet high humidity you need supplemental dehumidifier.

  3. #3
    SBKold, no I am not running fan constantly. It is currently set at 73 on auto. It turns on when temperature gets higher than 73 but the house keeps temperature well. It almost never turns on.
    Yes, this was their suggestion. Since one portion of house was warmer, they recommended 4 tons. No extra duct or vents. They did increase the size of the return.

  4. #4
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,051
    It will run more when its 85 -90 until 9pm.

    You just have low load right now since inside is same temp as outside.

    Look into a whole house venting dehum. It not only dehumidifies but brings in filtered fresh air.

  5. #5
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,758
    They increased the unit size by 33%. You may not have good humidity removal even when it warms up outside due to over sizing.

    A whole house dehumidifier. or a smaller A/C.
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  6. #6
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,428
    The air handler model number would be useful.

    It seems like the coil /air handler have been even more oversized ( I read " ... shooting massive amounts of cold air .." ) than the condenser.

    A four ton condenser with > 1,800 CFM seems like it could produce the symptoms that you describe.
    You may expect any cooling periods at < 90'F outside temperature to result in the unfavorable conditions (relative humidity > 53%) that you are currently experiencing.

    3 ton system set at 370 CFM per ton / ~1,100 CFM would definitely provide a significant decrease in humidity levels over a 4-ton with 1,800 CFM.
    + Shoulder seasons would be handled MUCH better.

    There's not much hope of a 4-ton unit ever providing low relative humidity in a tight house when it's less than ~ 83'F outside ( October - April).
    I know there is a lot of A/C use in south FL even in the so-called off-summer season.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  7. #7
    Hi Dan,

    Thanks for your response. The air handler model number is TAM4A0C48S41SBA. The condenser is 4TWR3048B1000AB.
    Should I go back to 3 ton? Would a 3.5 ton also be oversized?
    The 4 ton was recommended to help the fact that one side of the house was warmer during the summer.
    Thanks

  8. #8
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    a 2000sqft well sealed house even in Florida (which is more humid that hot) probably barely needs 3 tons. The best solution to your problem woudl have been either a 2 stage 3 ton or even going to a 2.5 ton or 2 tons depending on a load calculation. Longer run times will dramatically improve imbalances and a smaller sytem give you the flexibility ot balance the system by reducing airflow to overconditioend parts of the home.

    Increaseing hte size, absolutely made the problem worse, will have major humidity control problem, even if 2 stage, and you might even find that a new 13 or even 15 SEER 4 ton will use more energy than a properly sized 10 or even the same as a 8 SEER unit.


    Get a load calculaiton done. I bet you might even be best to go to 2.5 tons. OR answer this, even on the hottest days, was the old 3 tons running continously for at least 3-4 hours in the afternoon... I mean not cycling off at all WITHOUT using setbacks, just maintaining temperature? IF not, then it too was probably larger than you needed.

  9. #9
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    2,036
    As I didn't see it mentioned I'm guessing a cooling load calculation and ductwork evaluation wasn't done before they sold and installed the 4 ton system?

    A 2 stage and a simple zoning system could have been a better fit. But then I'm thousands of miles away and just throwing out ideas.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  10. #10
    Quote Originally Posted by firecontrol View Post
    As I didn't see it mentioned I'm guessing a cooling load calculation and ductwork evaluation wasn't done before they sold and installed the 4 ton system?

    A 2 stage and a simple zoning system could have been a better fit. But then I'm thousands of miles away and just throwing out ideas.

    Thanks for the help, I am very grateful. None of the estimates I got from the top rated contractors in my area said they needed to do a load calculation to determine the size of the unit. All of the estimates I got recommended a 4 ton. I am incensed that all of these people were wrong. I could understand 1 or 2 estimates, but all 5? All of them did go into the attic and look at the ducts (which are metal btw).

  11. #11
    On the hottest days (95 degrees, 76 degree dewpoints) the old 3 ton would not cycle off if I put the thermostat below 77. It would just run and run and never get below 77. It would finally go below 77 at night.


    Quote Originally Posted by motoguy128 View Post
    a 2000sqft well sealed house even in Florida (which is more humid that hot) probably barely needs 3 tons. The best solution to your problem woudl have been either a 2 stage 3 ton or even going to a 2.5 ton or 2 tons depending on a load calculation. Longer run times will dramatically improve imbalances and a smaller sytem give you the flexibility ot balance the system by reducing airflow to overconditioend parts of the home.

    Increaseing hte size, absolutely made the problem worse, will have major humidity control problem, even if 2 stage, and you might even find that a new 13 or even 15 SEER 4 ton will use more energy than a properly sized 10 or even the same as a 8 SEER unit.


    Get a load calculaiton done. I bet you might even be best to go to 2.5 tons. OR answer this, even on the hottest days, was the old 3 tons running continously for at least 3-4 hours in the afternoon... I mean not cycling off at all WITHOUT using setbacks, just maintaining temperature? IF not, then it too was probably larger than you needed.

  12. #12
    Join Date
    Jan 2008
    Location
    Texas
    Posts
    2,004
    Are the areas that were not colling before cooling now? If they are still a few degrees off you may be able to channel more air there which may permit it to run longer and offer a better balanced system. Your odds are slim otherwise to get the humidity down.

  13. #13
    Join Date
    Nov 2009
    Location
    Kansas City
    Posts
    124
    Yes you should have a load calc done. You would probably be best happy with a two stage unit with a variable speed blower to have a setup capable of dehumidification. How that works is the blower slows down which will remove the humidity then speed back up once the humidity level u want is reached. Sounds like in your situation that would be best. You can't just go and oversize a system and not compensate for it in other ways. I would get that contractor back out to help u come to a solution. If they are a good contractor they will get your comfort to how you want it.

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