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Thread: humidity

  1. #1
    Join Date
    Jul 2006
    Posts
    78
    Yes it's me again having problems again with my new a/c.
    Just a quick reminder. Had a 3 ton a/c and replaced it with a 3 1/2 ton and had all new duct work done too. We have finally gotten the new system to reach the desired temp.we have the tstat set for. However with our old system we were very cool and comfortable at 78 where as with our new one we are still hot at 75-76. I am in Northern CA where we have very low humidity. I couldn't figure out why were were so warm until my oldest son asked why the house was so humid...then it dawned on me that was the problem.
    At first I had the tstat set for a 2 degree differential then changed it to 1 as we were really warm as the house heated up. System runs for 20 minutes on and 20 minutes off since about 2:45 this pm...that is when the house got warm enough to turn the system on.It has only been in the high 80's here. However when I had the 2 degree differential it was still humid in here.
    Needless to say we will again have someone come out for this. I would like some advice on what can be done to control this humidity though, so I am somewhat informed when I speak to the a/c guys.

    Thanks again,
    Angela

  2. #2
    Join Date
    May 2006
    Location
    east central indiana
    Posts
    1,117
    Originally posted by angy400
    Had a 3 ton a/c and replaced it with a 3 1/2 ton
    Could be part of the problem here.
    -------------------
    A larger system in general will cool better but not dehumidify as well.
    It wasn't clear to me as to whether changing the differential helped.
    I believe you bought a two speed condenser, didn't you? If this is correct, how is it being staged?
    You could try slowing the blower which will allow a colder coil to grab more moisture as the air passes through it more slowly. Or a thermostat with dehum capability.
    Beyond that the fixes probably will begin to get more involved.

  3. #3
    Join Date
    Jul 2006
    Posts
    78
    Originally posted by 4l530
    Originally posted by angy400
    Had a 3 ton a/c and replaced it with a 3 1/2 ton
    Could be part of the problem here.
    -------------------
    A larger system in general will cool better but not dehumidify as well.
    It wasn't clear to me as to whether changing the differential helped.
    I believe you bought a two speed condenser, didn't you? If this is correct, how is it being staged?
    You could try slowing the blower which will allow a colder coil to grab more moisture as the air passes through it more slowly. Or a thermostat with dehum capability.
    Beyond that the fixes probably will begin to get more involved.

  4. #4
    Join Date
    Jul 2006
    Posts
    78
    [QUOTE]Originally posted by 4l530
    Originally posted by angy400
    Had a 3 ton a/c and replaced it with a 3 1/2 ton
    Could be part of the problem here.
    -------------------
    A larger system in general will cool better but not dehumidify as well.
    It wasn't clear to me as to whether changing the differential helped.
    I believe you bought a two speed condenser, didn't you? If this is correct, how is it being staged?
    You could try slowing the blower which will allow a colder coil to grab more moisture as the air passes through it more slowly. Or a thermostat with dehum capability.
    Beyond that the fixes probably will begin to get more involved.
    [/QUOT

    No changing the differential didnt help much at all. Yes we do have the stage blower but dont have the tstat with the dehum capability..would that help a lot? Not sure what you mean about the staging.

  5. #5
    Join Date
    May 2006
    Location
    Las Vegas,Nevada
    Posts
    339
    Staging would refer to the unit running on low to dehumidify and go to high on the call for cooling.If it's not staged correctly,then your running at full speed until desired temp then it shuts down.A t-stat with dehum feature will run the system on low to remove moisture and make you more comfortable.
    P.S. Some problems may have been brought on by going to a larger unit but I'm SURE you had the load calcs done,right??

  6. #6
    Join Date
    Jul 2006
    Posts
    78
    Originally posted by smngmu
    Staging would refer to the unit running on low to dehumidify and go to high on the call for cooling.If it's not staged correctly,then your running at full speed until desired temp then it shuts down.A t-stat with dehum feature will run the system on low to remove moisture and make you more comfortable.
    P.S. Some problems may have been brought on by going to a larger unit but I'm SURE you had the load calcs done,right??
    Yes load cal. was done. My smaller unit was never able to meet tstat setting and would run nonstop on hot days, but the air was much drier and cooler. I will bring up the setting then when the guys come out. What are proper humidity levels for a house?
    Thanks!

  7. #7
    Join Date
    May 2006
    Posts
    312
    angy400 wrote:
    > My smaller unit was never able to meet tstat setting and would run nonstop on hot days

    Your own words above are the key to understanding your current dilemma. You *want* a system that is slightly undersized so that it runs as long as possible. A typical 2-stage system uses a variable speed motor varying not only the blower speed but also compressor.

    When temps outside are in the 78 to 89F range, I run exclusively with a 1.5 ton compressor (stage 1) which maintains a 2000 sq ft house at 77-78F and RH% between 44-48%. The small 1.5 ton compressor runs almost non-stop which is fine as it consumes only 1260 watts of power (less than my pool pump).




  8. #8
    Join Date
    Jul 2006
    Posts
    78
    sorry..I dont have a 2 speed compressor..its a 2 speed furnace, single speed condensor.

    Nina,
    Yes with my udersized unit never had any probs with humidity as it ran constantly..however the tstat never could get below 78 degrees on an average day and if we had a heat spell and extra bodies in the house, then it really got warm.

  9. #9
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    1,380
    What is the heat gain of the house?

    They should be able to modify the blower speed to help with the humidity. If the system is oversized it still might not dehumidify properly.

  10. #10
    Join Date
    Feb 2004
    Location
    Ontario
    Posts
    700
    You haven't posted the RH% in your home. You haven't actually measured it and are just guessing this is the problem. (You may well be right). Why don't you get a hygrometer for measuring the RH, from Radio Shack or Home Depot or somewhere and take an actual measurement. They're pretty cheap instruments. RH below 50% is pretty comfy, above 60% is pretty sticky.

    BTW, was your thermostat replaced when the new a/c was installed? May just be calibrated different from the previous stat.
    Question authority!

  11. #11
    Join Date
    Jul 2006
    Posts
    78
    Originally posted by jetstream
    You haven't posted the RH% in your home. You haven't actually measured it and are just guessing this is the problem. (You may well be right). Why don't you get a hygrometer for measuring the RH, from Radio Shack or Home Depot or somewhere and take an actual measurement. They're pretty cheap instruments. RH below 50% is pretty comfy, above 60% is pretty sticky.

    BTW, was your thermostat replaced when the new a/c was installed? May just be calibrated different from the previous stat.
    Jet,
    I havent taken a reading as I dont have any instruments to do so. I just know with the air set at 75-76 we are still warm and somewhat sweaty. This morning I made a peanut butter sandwich for my son to take and the peanut butter was soft, almost as if melted! Never had that happen before.
    I will send hubby to the store to buy an instrument to gauge the humidity..and yes we had a new tstat installed along with the new unit.

  12. #12
    Join Date
    Jul 2006
    Posts
    78
    OK bought a hygrometer and now without air on the humidity is 56%. This hygrometer also has a thermostat on it and the reading in the hall says the temperature is 76 where as my tstat says its only 73 degrees. The tstat has been calibrated 2x by the air guy as we were at first having a problem with temps rising when air was on instead of going down. A/c guy patched holes in wall behind tstat and the temp went down immediately. So now I am unsure how well my tstat is reading. Anyway have air set on 75 today and will see what my humidity is.

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