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  1. #40
    Join Date
    Jun 2008
    Location
    In the Boondocks near Marion, IN
    Posts
    119
    The thermometer probe needs to be inserted directly into the register. Same with the measuring the RH.
    Rick

    "It is easier to do things right the 1st time rather than to explain why it wasn't when you have to do it the 2nd time."

  2. #41
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,295
    Quote Originally Posted by Dr Gaius Baltar View Post

    The main air return is about 72 at the end of the cooling cycle,
    humidity about 62%.

    I didn't get 50-55F at the register and 80-90% humidity.

    I had the meter placed about 6 inches away from the register.
    Was I not placing it close enough?
    Good hygrometer needs to be practically placed "in the duct" close the the air handler.

    Set T'stat to 77'F may decrease RH to 49 - 53% on a hot day.

    One will never consistently achieve < 50% RH at 72'F with 2-stage unit
    without VERY LOW air flow rate.
    Coil must maintain less than 52'F dew point (ADP).
    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

  3. #42
    My temperature reader doesn't have probes that I can put in the register, it's one of these:
    http://www.amazon.com/AcuRite-613-In...erature+reader

  4. #43
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,125
    Place it against the register.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  5. #44
    Okay, I placed the temp reader up against the register. Here are my findings:

    nearest register to furnace: after AC ran 23 minutes, 88% humidity, 64F
    farthest register from furnace: after AC ran 20 minutes, 85% humidity, 64F

    The temperature is 84 outside, 61% humidity, still 73 inside the house at the thermostat, AC still set at 73 and fan on AUTO.

  6. #45
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,125
    Coil not cold enough, or your return is drawing in unconditioned air.
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    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  7. #46
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,125
    Look around the air handler and see if you see any openings in the return duct.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  8. #47


    I wasn't sure which one of these pipes is the return air duct, so I took a picture to show you what I mean. If that's the correct duct (the big metal pipe with the red line pointing to it, with the white paintish stuff around it), then I don't really see any holes in it.

    I can feel some air coming out of the lines that I indicated at the bottom of the picture, and in the bottom right I have magnified that area to show it in detail. Is that normal?

    Does that white pipe coming out of the coil (I think that's the coil) look right, or does it look problematic? It leads to the outside, where it drains onto the grass.

  9. #48
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    21,188
    Quote Originally Posted by beenthere View Post
    Coil not cold enough, or your return is drawing in unconditioned air.
    X2...

    When the tech comes out, have him lower the fan speed a bit... Meanwhile, examine the entire return ducting as best you can for any cracks or loose joints. You can have the installing co repair them, or you can buy a roll of foil tape at the local hardware store and add some 'sweat equity' to your home. An aid to finding leaks in a duct system is to stick a really bright lite inside the duct, then examine it from the outside. Keep moving that lite along the duct and examining the outside. One thing I find on many installs: The filter holder door is loose and/or has cracks one can stick things through... Get yourself a roll of painter's masking tape--every time you change the filter, seal up the cracks. You would be amazed how small a crack will raise the RH in a home 10% or more.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  10. #49
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    21,188
    Quote Originally Posted by Dr Gaius Baltar View Post


    I wasn't sure which one of these pipes is the return air duct, so I took a picture to show you what I mean. If that's the correct duct (the big metal pipe with the red line pointing to it, with the white paintish stuff around it), then I don't really see any holes in it.

    I can feel some air coming out of the lines that I indicated at the bottom of the picture, and in the bottom right I have magnified that area to show it in detail. Is that normal?

    Does that white pipe coming out of the coil (I think that's the coil) look right, or does it look problematic? It leads to the outside, where it drains onto the grass.
    The white pipe is the condensate drain, it looks fine in the picture. Important thing there is a good slope and water flowing freely!
    Yes, the box on top of the furnace is the coil. Is it level or sloping just a tiny amount forward? If it is sloping backwards, or away from the drain, that is not a good thing.
    The rectangular metal box going down to the bottom left of the furnace is the return. Best if every crack and nook and hole is filled.
    The holes with the copper lines on the coil are not a big deal, they are letting conditioned (heated or cooled) air into your utility room.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  11. #50
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,125
    The pipe the red line runs to is a return duct. but you have other returns. need to check them all.
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    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  12. #51
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,452
    Quote Originally Posted by Dr Gaius Baltar View Post
    Okay, I placed the temp reader up against the register. Here are my findings:

    nearest register to furnace: after AC ran 23 minutes, 88% humidity, 64F
    farthest register from furnace: after AC ran 20 minutes, 85% humidity, 64F

    The temperature is 84 outside, 61% humidity, still 73 inside the house at the thermostat, AC still set at 73 and fan on AUTO.
    With 73^F return, a we would need a <50^F dew point supply air. 64^F, 85% RH is 58^F dew point. Estimate a 50-53^^F coil temp, lower the air flow through the cooling coil to get a 45^F coil temp. This would lower the supply air to 55^F, 85%RH, a 51^F dew point. Slower fan speed or a more restrictive air filter will slow the air flow. During high cooling loads, this should provide 50%RH at 73^F. If not slow air flow more yet. This lengthens the cooling cycle. Fan "auto". during low/no cooling loads, a small whole house dehumidifier will maintain <50%RH.
    Help us train your a/c tech.
    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"

  13. #52
    The white pipe has a downward slope and the coil box appears to be level. Outside there are little tiny pools of water popping up on the grass where the drain pipe is draining water/coolant or whatever that substance is.

    It doesn't seem like there are any leaks on the return, but it's cramped and I can't really get a good look at it. The only place that seems to have any air coming out of it is near the copper lines that I talked about earlier. From what I can access, anyway.

    Teddy Bear, that sounds good, I will definitely ask again for the tech to adjust the fan speed or ramp profile when he shows up again.

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