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Thread: high humidity

  1. #14
    Join Date
    Dec 2005
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    1,918
    Quote Originally Posted by high humidity View Post
    Hello i have a 3 ton r-410 condensor and 3 ton furnace and a 3 ton r410 coil with txv. The whole system is oversized by a ton for a 1,000 square ft hom in Houston. Could i change the condenser to a 2 ton r410 and have it work with the 3 ton furnace and coil? Thank You
    1 ton over-size evaporator coil won't creat more humidity if it is setting up correctly.

    To simple answer your question is "YES"

  2. #15
    Quote Originally Posted by tinner73 View Post
    can you lower the blower speed any more?
    When I had my furnace checked out in Oct i had the Tech lower the fan speed to medium. When i asked him if i could lower it to low he told me the coil might freeze up. The fan speed at medium don't feel much lower than the high setting? Thank you

  3. #16
    Quote Originally Posted by just_opinion View Post
    1 ton over-size evaporator coil won't creat more humidity if it is setting up correctly.

    To simple answer your question is "YES"
    Hello and thank you for your reply, I am confused on the answer. 1 ton over-size evaporator coil won't creat more humidity if it is setting up correctly
    Will it create less humidity if it is set up right? or would dropping the fan speed to low do just as good, if the coil does not freeze up.

  4. #17
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    Dec 2005
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    Quote Originally Posted by high humidity View Post
    Hello and thank you for your reply, I am confused on the answer. 1 ton over-size evaporator coil won't creat more humidity if it is setting up correctly
    Will it create less humidity if it is set up right? or would dropping the fan speed to low do just as good, if the coil does not freeze up.
    That is for the qualified technician to give you the solution. I don't mean to be rude.

    It is very very easy to deal with sensible heat (dry bulb temperature). And I did emphasize the word very.

    But when it comes to latent heat (wet bulb temperature). It is very difficult in the sense that you don't want to compromise the punishment that the equipment will take it it is not done properly

  5. #18
    Join Date
    Feb 2004
    Location
    chicago suburbs
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    i'd start with lowering the fan to low. if you don't have freezing issues.. problem solved. if freezing occurs then get the right size equipment.

  6. #19

    lowering the fan to low

    Quote Originally Posted by tinner73 View Post
    i'd start with lowering the fan to low. if you don't have freezing issues.. problem solved. if freezing occurs then get the right size equipment.
    Thank you very much for your time, I will have the tech do it when he comes.

  7. #20
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    Dec 2005
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    Quote Originally Posted by tinner73 View Post
    i'd start with lowering the fan to low. if you don't have freezing issues.. problem solved. if freezing occurs then get the right size equipment.
    Now you see what I mean by compromising the unit when you are dealing with latent (humidity ) heat.

  8. #21
    Quote Originally Posted by just_opinion View Post
    Now you see what I mean by compromising the unit when you are dealing with latent (humidity ) heat.
    Thank You very much for your help

  9. #22
    Join Date
    Jun 2004
    Location
    Kathleen GA
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    236
    See Teddybear's comment for 99% answer. The other 1% is to consider a two speed compressor. That will give you good humidity control.

  10. #23
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    6,436
    Quote Originally Posted by alex_in_fl View Post
    See Teddybear's comment for 99% answer. The other 1% is to consider a two speed compressor. That will give you good humidity control.
    Appreciate your support. But with low/no cooling load, single speed or two speed will not remove enough moisture to maintain 50%RH.
    Another comment of slowing the fan to a lower speed, I tuned my old system to remove max latent. If I cooled below 74^F, the a/c coil would freeze. I did not cool below 76^F. A system slowed to the minimum air flow to remove max latant will freeze-up with cooling below a cvouple degrees below your lowest temperature. I needed 10 hours of cooling load to maintain <50%RH. If you are getting an air change of fresh air every 4-5 hours with 4 occupants, you should remove 50-75 lbs. of moisture everyday. Combining a properly set-up a/c with a good whole house dehumidifier makes this a piece of cake. Set the temperature and %RH you want forget it. Plus you can have the ideal amount of fresh air for indoor air quality. Lets keep the Ventilation in HVAC. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  11. #24
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    18,836
    Quote Originally Posted by high humidity View Post
    Thank You very much for your help
    Tinner may be correct.Find a company that can test the static,use the mfrs. fan chart and set the air floe correctly,might make all or enough of the difference needed.


    Post all the model numbers and someone with the fan chart can give you a better idea.

  12. #25
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    Quote Originally Posted by ascj View Post
    My home system that is a 2 ton condenser with a 3 ton evap, is only .01% different S/T than they same condenser with 2 ton evap.
    .
    How can I determine that data? I have a 4 Ton coil for my 3 Ton XL16i and I'm concerned I made a mistake and should have gone with a 3 Ton coil which only gave up 200 BTU of cooling and 0.25 SEER. I'm especially concerned about humidity removal in low stage which is about 2.2 Tons.

    I read a study from the mid 80's that showed no correlation between face area of a coil and dehumidification. I suppose the lower face velocity of the larger coil balances the slighly higher surface temerature.

    On the other hand, my old 8 SEER system was being supplied almost 500 CFM/ton of airflow and it still seemed to dehumidify pretty well. It's capacity was probably reduced as well from it's age, and the mismatched coil it had.

  13. #26
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    5,520
    This might be a weird idea, but instead of a whole house dehumidifier, I wonder if you could use a heat pump to defrost the indoor coil on demand? I wonder if you could use the existing coil temperature sensors to do this? Or use the heat pump to add heat to the home when you've reached the setpoint, but you need further dehumidification. What issues would you have running the heat pump at high outside temperatures?

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