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Thread: humidity

  1. #27
    Join Date
    Dec 2006
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    Middle Tennessee
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    11,347

    *

    Quote Originally Posted by NGHTYRTE View Post
    Kirtusjon-- Do I Leave Or Believe
    i think you dont understand what you have been told

    or are you trying to be funny



    .

  2. #28
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Wow we have a live one on this thread.

  3. #29
    Join Date
    Jul 2007
    Location
    South Florida
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    153
    Quote Originally Posted by NGHTYRTE View Post
    Kirtusjon-- Do I Leave Or Believe


    We don't have to agree on this. This my opinion from my experance here in South Florida. I do not mean any disrespect to anyone here on this form. If I don't agree, I will say so. That's all. I do not think I know everything there is to know in this business. I have not had 1 person explain the other point of veiw, only that it won't create humidity.
    Too Few Pro Tech's & Too Many Parts Changer's.

  4. #30
    Join Date
    Jul 2007
    Location
    SA
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    127
    Quote Originally Posted by NGHTYRTE View Post
    Kirtusjon-- Do I Leave Or Believe
    hey you got over 15 post why don't you apply for pro membership

  5. #31
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,062
    http://www.wunderground.com/history/...lyHistory.html
    This is the weather for the last month in central FL.
    I do not see enough cooling load to remove enough moisture from properly ventilated, occupied home. You need 75 cfm of fresh air in a home with four occcpants. This is 3-4 lbs. of moisture per hour. This equates to3,000-4,000 btus of latent load per hour. Ideally setting up a a/c with a near freezing coil requires 12,000 btus of every hour to remove the moisture.
    By having an air tight home without enough fresh air, the moisture load is about 1lb. per hour. This is much lower moisture load. Most dry homes in green grass climates during wet cool weather are not getting the fresh air to purge indoor pollutants and renew oxygen. With outside temperatures below the indoor stat setting, the a/c does not operate. With adequate fresh air change and moisture from the occupants, the indoor moisture content will be higher than outside.
    Adding 4 lbs. dehumidification per hour allows real humidity control with fresh air ventilation and without any a/c opperation regardless outdoor temperatures. 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"

  6. #32
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,086
    Quote Originally Posted by NGHTYRTE View Post
    i am curious how fan on all the time hurts hum. in homes. fan on is allways good. cost a little more but the benefits are worth it
    You've already been hammered with one point regarding running the indoor blower between compressor cycles...indoor air humidity levels will rise between cycles.

    They will rise for more than one reason, possibly. Evaporation from the coil and drain pan is obvious. That point should not even be in dispute. To do so is to blatantly ignore a plain law of physics.

    Another contributor is when supply air ducts run through an attic and leak air to the attic. This will place the interior spaces of the house into a negative air pressure in respect to outdoor air. Outdoor air in Florida during the cooling season is hot and humid. If it is pulled into the house via cracks and gaps in construction, it will raise humidity levels in the house, along with temperature. Solution? Either make every last stitch of supply ducting airtight, make the house envelope airtight, or simply turn the blower off.

    Guess which one is easiest and cheapest?

  7. #33
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    5,987

    Smile Comfort level is subjective .. but try ASHRAE 55 for a STANDARD

    Quote Originally Posted by cjones215 View Post
    I have a 2 year old home in central florida. It is always humid (around 50 to 52 percent RH). I have measured humidity in other homes (friends and relatives) and they always measure in the very low 40's.

    It seems damp to me and setting the AC on 75 degrees is just too hot in the home.

    Do I have a problem or does this sound normal ??
    < 45&#37; R.H. is not to hard to obtain if one sets the indoor temperature to
    ~77'F.

    Programmable t-stat can be set to 82'F during the day/weekday.

    77'F with Low R.H. at times seems chilly ...
    transplanted Michigan native
    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

  8. #34
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,086
    Some quick data just gathered regarding humidity increase via blower running after compressor shuts off.

    Measured room temperature and humidity level with Testo H2 digital psychrometer, which happens to be pretty doggone accurate, I've found. Tested it against a sling psychrometer at some point, it did not disappoint.

    Room temp 75 degrees/51&#37; RH. A/C kicked on. Inserted H2 into ceiling round diffuser and observed as supply air temp stabilized at 55 degrees dry bulb and 80% RH. Compressor then clicked off and indoor blower went into "blower off delay" mode, running for another minute or so until timing off. Before blower stopped, discharge humidity from diffuser rose to 96% and dry bulb to 60. In just over a minute.

    I then picked up the H2 during the next cycle and observed room conditions from my seated position. Started out at 75/52, dropped to 73/48 when system ran. Compressor clicked off, blower kept running. Humidity quickly spiked to 55% before blower shut off, then settled down toward 51% as room air in motion continued mixing and settling.

    If I can find a way to kill that blower off delay, I'm gonna do it.

  9. #35
    Join Date
    Jun 2007
    Location
    Central, FL
    Posts
    870
    Quote Originally Posted by shophound View Post
    Some quick data just gathered regarding humidity increase via blower running after compressor shuts off.

    Measured room temperature and humidity level with Testo H2 digital psychrometer, which happens to be pretty doggone accurate, I've found. Tested it against a sling psychrometer at some point, it did not disappoint.

    Room temp 75 degrees/51% RH. A/C kicked on. Inserted H2 into ceiling round diffuser and observed as supply air temp stabilized at 55 degrees dry bulb and 80% RH. Compressor then clicked off and indoor blower went into "blower off delay" mode, running for another minute or so until timing off. Before blower stopped, discharge humidity from diffuser rose to 96% and dry bulb to 60. In just over a minute.

    I then picked up the H2 during the next cycle and observed room conditions from my seated position. Started out at 75/52, dropped to 73/48 when system ran. Compressor clicked off, blower kept running. Humidity quickly spiked to 55% before blower shut off, then settled down toward 51% as room air in motion continued mixing and settling.

    If I can find a way to kill that blower off delay, I'm gonna do it.
    Carrier has the same blower delays, they have this small metal jumper on the side of the fan control board. If you cut that it removes the off delay on the fan, its a pain in the azz some times if you forget to remove that jumper & the inspector is testing the smoke detector
    WARNING:IF YOU DON'T KNOW THEN DON'T DO, SO THOSE WHO KNOW WHAT YOU DIDN'T KNOW DON'T END UP UNDOING WHAT YOU DID SO IT COULD GET DONE RIGHT!

  10. #36
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,086
    Quote Originally Posted by AcDOCnTRAINIG View Post
    Carrier has the same blower delays, they have this small metal jumper on the side of the fan control board. If you cut that it removes the off delay on the fan, its a pain in the azz some times if you forget to remove that jumper & the inspector is testing the smoke detector
    I haven't dug into my furnace much yet to see if it's possible. It's a Rheem...will need to get model no. off it at some point. I'm a heavy commercial guy, don't do much resi now (though I have in the past), but if there's no jumper to disable blower off, I'll think of some other way to make it happen.

    The TXV may be a hard shut off (non-bleed), and if that's the case, a blower off delay is even more pointless, as, to my understanding, the blower off delay was designed with piston/flow raters in mind; after the compressor shuts off, refrigerant is still traveling through the coil due to a pressure difference (albeit a decreasing difference) and some measure of refrigerating effect remains...kind of a "free cooling" approach.

  11. #37

    some details on the house

    My home is just under 1800 sq. ft. Only the living room has a vaulted ceiling.
    The unit is a 3 1/2 ton Carrier. I had the service tech out here many times. They rerouted some duct work, they changed a valve in the air handler but they never licked the problem.
    I am measuring with a small digital thermometer that also measures RH. I realize that the device may not be accurate but there is a consistent difference between my house and all the others I measure. One of the comments states that 44% is right. I agree. It seems that somewhere around 42 to 44 makes a big difference.
    Another comment was about the delay feature on the fan. I think that may be a problem too. I would love to turn that thing off. I also have observed Humidity spikes after the compressor turns off.
    By the way, the house is well insulated and air tight. The slab had a vapor barrier and screen rebar. They did not use the fiberglass base concrete. The block walls are insulated with the foil backed foam.. (forget what they call it).
    Thank you all for your input. I tend to think the unit is too big. Just my opinion.

  12. #38
    Join Date
    Mar 2008
    Location
    dalton ga
    Posts
    39

    Humidity

    people--humidity causes all kinds of prob. i wood love to talk to anyone about it... and no im not kidding!!!

  13. #39
    Join Date
    Mar 2008
    Location
    dalton ga
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    39
    Quote Originally Posted by Airmechanical View Post
    i think you dont understand what you have been told

    or are you trying to be funny



    .
    i may not have understood the the ? but i know a/c-r make me understand please.

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