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  1. #1
    Join Date
    Jan 2008
    Location
    Louisville,ky
    Posts
    32

    I've got a silly question about humidity

    I run my furnace fan on all the time for air conditioning.Now when I check my humidity, with Digital sling psychrometer,I get a reading 49% the temp. is at 76 indoor and outdoor temp is 86.Now my question is,when I check humidity when the A/C calls for cooling,than the furnance fan comes on in the auto position same temp.indoor and outdoor run it awhile,my humidity drops to 39%, just by having the fan come on with the A/C unit.So my point is,it still better to let the fan run all the time.THX

  2. #2
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    Most of the time your fan will consume enough KWH it will not be a good idea in terms of electric bills. There is an argument about humidity but from your report there is little to complain about. Probably you will see higher humidity if you let the fan run constantly without the AC.

    Hope this helps -- Pstu

  3. #3
    Join Date
    Jan 2010
    Posts
    6,206
    Quote Originally Posted by etap View Post
    I run my furnace fan on all the time for air conditioning.Now when I check my humidity, with Digital sling psychrometer,I get a reading 49% the temp. is at 76 indoor and outdoor temp is 86.Now my question is,when I check humidity when the A/C calls for cooling,than the furnance fan comes on in the auto position same temp.indoor and outdoor run it awhile,my humidity drops to 39%, just by having the fan come on with the A/C unit.So my point is,it still better to let the fan run all the time.THX
    The only time your dehumidifing is when your a/c is running.

  4. #4
    Join Date
    Nov 2008
    Location
    Bristol Va.
    Posts
    450
    when the fan is blowing room air across a wet evap. coil with water in the drain pan you will um how do I say pick up humidity and put it back into the house.

    this is why I never recommend running the fan in the summer.

    dogboy

  5. #5
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,271

    Thumbs down Stop it now



    N O ! !!


    Quote Originally Posted by etap View Post
    I run my furnace fan on all the time for air conditioning.

    So my point is,it still better to let the fan run all the time.THX
    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

  6. #6
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,931
    Quote Originally Posted by VTP99 View Post
    The only time your dehumidifing is when your a/c is running.
    And the only time your IAQ features are working is when the blower is running. It depends on what kind of blower you have, what the settings are on the blower, what IAQ products are installed and what the stratification conditions of the house is as to whether or not it is a good idea to run the blower all of the time.

    I want my filter to be functional 24/7, so my blower runs 24/7. For the first time, I now have a variable speed blower. So, even though I never saw high electric bills from my previous psc motors, it will be even less now.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  7. #7
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,177
    If you want higher humidity in the house, set the furnace blower to a higher cooling speed.

  8. #8
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,931
    Quote Originally Posted by 54regcab View Post
    If you want higher humidity in the house, set the furnace blower to a higher cooling speed.
    Why would anyone want higher humidity during the cooling season?
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  9. #9
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,177
    Quote Originally Posted by RoBoTeq View Post
    Why would anyone want higher humidity during the cooling season?
    I guess I didn't quite understand the OP's question. It seems like he wants the humidity around 49%?

  10. #10
    Join Date
    Jan 2008
    Location
    Louisville,ky
    Posts
    32

    No I don't want 49% I just not aware the differences

    I've always left my fan in on position,because I thought it makes the temp.more even,plus the filter will do a better job,with the fan running,compare not moving any air,only on demand.
    I couldn't belive the differences,to remove humidity you would want to leave the fan in auto position,but if you want cool two storys,you would want to leave the fan on,right. THX

  11. #11
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,931
    Quote Originally Posted by etap View Post
    I've always left my fan in on position,because I thought it makes the temp.more even,plus the filter will do a better job,with the fan running,compare not moving any air,only on demand.
    I couldn't belive the differences,to remove humidity you would want to leave the fan in auto position,but if you want cool two storys,you would want to leave the fan on,right. THX
    Depends on what is most important to the circumstances. Or, as one guru of wisdom would say; "You can't always get what you want, but if you try sometime, you just might find, you get what you need."
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  12. #12
    Join Date
    Nov 2008
    Location
    Bristol Va.
    Posts
    450
    I went to a call yesterday, compaint was too high of humidity level 71* and 75% rh. I asked him how long it had been too high and he said 2 weeks. We went to his t-stat and the fan was in the on position, I asked him how long the fan had been on he said about 2 weeks.

    I turned the fan to auto, let the a/c cycle once and almost 30 minutes after the a/c had shut off his humidty level was 70%. I don't know what stratification is but I do know more times than not fan on in summer raises the humidity level.

    dogboy

  13. #13
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,271

    Angry $$$ for Fans

    Quote Originally Posted by etap View Post
    I've always left my fan in on position,because I thought it makes the temp.more even,plus the filter will do a better job,with the fan running,compare not moving any air,only on demand.
    I couldn't belive the differences,to remove humidity you would want to leave the fan in auto position,but if you want cool two storys,you would want to leave the fan on,right. THX
    1 hp .... = 746 watts
    1 month = 720 hours
    1 hp-month = 537,120 watt-hrs = 537.12 kw-hrs

    @$0.10 /kw-hr = $53.70 / month = $644.54 / year

    ........... That's about 7, 8 or 9 months of electric bills for me.


    _______ 1/2 hp = $26.86 / month


    $$$ .. This is not cents

    or Is nonsense to me.

    Run any fans or pumps on an interval / timer.
    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

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