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  1. #1

    Coleman heat pump will not dehumidify

    I have tried to read all the posts on this topic but still would like some help. I had a new heat pump installed two years ago. We had some issues with it on the heating side and they replaced the air handler last winter. Since then the humidity never gets below 50rh And most of the time it is in the mid 50's. They have tried many different thing but to no avail,( they in larged the ducts). Last week they changed the variable fan and slowed the air flow down. The RH dropped to the low 50's. Of course some of that might be the outside RH is lower. I have a Colman 8t I think and it is a 15 or 16 seer in a ranch style home with vaulted ceiling in part of the house. And it is 1400 sq ft. I am sure this is not enough info but if I had some questions to ask or suggestions for them, that would help. Thanks in advance.

  2. #2
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    Model numbers of both indoor and outdoor equipment, should be located on the data plate on units

  3. #3
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    Quote Originally Posted by virstens View Post
    I have tried to read all the posts on this topic but still would like some help. I had a new heat pump installed two years ago. We had some issues with it on the heating side and they replaced the air handler last winter. Since then the humidity never gets below 50rh, And most of the time it is in the mid 50's.
    Relative Humidity in the 50's in January
    would be a real issue with the Humidifier set Too High.
    Designer Dan
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  4. #4
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    I have tried to read all the posts on this topic but still would like some help. I had a new heat pump installed two years ago. We had some issues with it on the heating side and they replaced the air handler last winter. Since then the humidity never gets below 50rh And most of the time it is in the mid 50's.
    They have tried many different thing but to no avail,( they enlarged the ducts). Last week they changed the variable fan and slowed the air flow down. The RH dropped to the low 50's. Of course some of that might be the outside RH is lower.
    I have a Colman 8t I think and it is a 15 or 16 seer in a ranch style home with vaulted ceiling in part of the house. And it is 1400 sq ft. I am sure this is not enough info but if I had some questions to ask or suggestions for them, that would help. Thanks in advance.
    Do U live in a humid climate; where?

    What kind of ceiling lights do U have? Hot attic air infiltration will cause humidity problems...

    All U need is a good thermometer (digital reading in tenths preferable) and an indoor Humidity Gauge

    1) Tonnage & SEER of Unit &/or outdoor condenser model number: Minimum SEER upped to 10-SEER in 1987; upped to 13-SEER in 2006

    2) TXV or, orifice metering device? _______. Only if U know…

    3) Outdoor condenser’s discharge-air-temperature ______-F
    Subtract Outdoor air temperature: _______
    Outdoor Condenser Air-Temp-Split _______

    4) Need the ‘Indoor’ percent of relative humidity - in the middle of the rooms or, at Return-Air inlet grilles ___

    5) Indoor Return-Air Temperature ______
    Subtract Indoor Supply-Air Temperature ______ -F
    Indoor temperature-split _______-F

    We need the above information for troubleshooting humidity problems & performance analysis.
    Last edited by udarrell; 09-02-2012 at 09:43 AM. Reason: Typo + kind of ceiling lights

  5. #5
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    Need Model num ber of both the outdoor unit and the air handler and the evap coil if its a modular air handler.
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  6. #6

    my humidity

    Quote Originally Posted by beenthere View Post
    Need Model num ber of both the outdoor unit and the air handler and the evap coil if its a modular air handler.
    I will try to answer all the questions that i can. I live in South Dakota
    outside unit model HC8B024F-1C
    indoor unit AHR36B3XH21A
    it is an 8T unit
    i can not find the Seer reading but i remember it was more than 15 but less than or equal to 18?

    wall stat set to 75 and is maintaining 75 it's humidity reading is 54 rh

    I purchased the battery operated temp humidity gauge.

    the out put air is 72 degrees and 51 RH at the vent
    the return air 73 degrees and 54RH

    i put the unit outside on the deck and got 90 degrees and 46 RH

    I check the local tv station and they have 93 degrees and 38 RH As you can see the RH is lower outside than in. ????

    most of the cellings in my house are vaulted and most lites are table lamps or a wall lite in each bedroom.

    The space above the bathroom and hallway is in closed to make an attic type of area. that is where they put the air handler. (same place that the old air handler was when i had the Ruud a/c before this one.) this area has a common wall to each room in the main part of the house. I did add an addition that they ran duct work to. They put a small temp sensor in this added bedroom to help match the readings from the other part of the house.

    The other day they replaced the variable speed fan with another one and slowed down the fan alot. It seem to reduce the RH from 55 to 51 but that is all. The wife tells me they have been out with numerous gauges, tester and seemed to have checked all types of readings.

    As i mentioned in a thread above this is the second air handiler, they replaced it last winter when it could not maintain the temp when heating when switching from heat pump to aux heat.

  7. #7
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    RH is relative to temp. The air in your home actually has less moisture in it.

    When you measured the air temp and RH from the supply, was the A/C running?

    Good chance they never set up the blower.
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  8. #8
    Join Date
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    It's a 2 ton outdoor unit with a 3 ton air handler. The blower motor may not be set up correctly to Match the outdoor unit capacity. If the ac was on when you took that temp then something is terribly wrong. I'm assuming it was just the fan running.

  9. #9
    [QUOTE=jtrammel;14108741]It's a 2 ton outdoor unit with a 3 ton air handler. The blower motor may not be set up correctly to Match the outdoor unit capacity. If the ac was on when you took that temp then something is terribly wrong. I'm assuming it was just the fan running.[/QUO

    The wall stat was set to auto and cool and the fan was running. I believe the outside unit was running

  10. #10
    Would it help to set the temp to 72 degrees

  11. #11
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    You need to have the room thermostat set on AUTO; U may have it set on ON & therefore the condensing unit outdoors may not have been running.
    The wall stat was set to auto and cool and the fan was running. I believe the outside unit was running.
    Well, I had overlooked your statement; but I still don't believe the outdoor compressor was running!

    The system will dehumidify better using AUTO; also, the oversized indoor coil tends to raise the temp of the indoor coil higher than with a 2-Ton coil would.

    Some areas of South Dakota have rather low % of relative humidity, as beenthere stated:
    beenthere:
    RH is relative to temp. The air in your home actually has less moisture in it.

    When you measured the air temp and RH from the supply, was the A/C running?

    Good chance they never set up the blower.
    The air coming out of the supply outlets will always have a higher humidity; do your testing at the return air grilles or well away from any supply outlet diffusers.
    Last edited by udarrell; 09-02-2012 at 07:40 PM. Reason: higher humidity...

  12. #12
    [QUOTE=udarrell;14109591]You need to have the room thermostat set on AUTO; U may have it set on ON & therefore the condensing unit outdoors may not have been running.

    Well, I had overlooked your statement; but I still don't believe the outdoor compressor was running!

    The system will dehumidify better using AUTO; also, the oversized indoor coil tends to raise the temp of the indoor coil higher than with a 2-Ton coil would.

    Some areas of South Dakota have rather low % of relative humidity, as beenthere stated:

    The air coming out of the supply outlets will always have a higher humidity; do your testing at the return air grilles or well away from any supply outlet diffusers.[/QUOTE


    If I had a system that was working correctly. What humidity should I expect it to maintain? I don't want to be unrealistic

  13. #13
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    Might help a little. But your A/c is not set up right, and it could lead to an early failure of your compressor.
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