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  1. #1
    Join Date
    Feb 2007
    Location
    Bellingham, WA
    Posts
    115

    At the end of a call for heat, my HP is cooling my house!

    I have a York duel fuel system. The settings on my thermostat are as follows:

    1. Fan = ON
    2. Heat = 68F
    3. OD temp = 40F
    4. ID temp = 68F
    4. BP = 35F

    I placed a digit thermometer at the furthest register from my furnace/A-coil. It is located on the second floor at the opposite end of the house. When there is a call for heat, the thermometer eventually reads ~7 to ~10 above 68F. When the call for heat cycle ends, the temperature reading slow declines until the output temperature is ~66F (less than ID temp).

    Is this a "problem" with all HVAC systems when the fan is set to ON? Is there a fix to this problem?

    Thanks.

  2. #2
    Join Date
    Apr 2007
    Posts
    6,285
    duct insulation or lack of?

  3. #3
    Join Date
    Feb 2007
    Location
    Bellingham, WA
    Posts
    115
    Quote Originally Posted by BigJon3475 View Post
    duct insulation or lack of?
    BigJon is correct. I don't have any duct insulation and it is unlikely that I could add insulation without spending big $.

    BigJon are you saying that I can't fix this problem (SOL) without adding duct insulation.

  4. #4
    Join Date
    Apr 2007
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    6,285
    Quote Originally Posted by jechow View Post
    BigJon is correct. I don't have any duct insulation and it is unlikely that I could add insulation without spending big $.

    BigJon are you saying that I can't fix this problem (SOL) without adding duct insulation.

    You could cut the fan to the auto position so it shuts off after running ....probably on a delay to take advantage of any left over heat in the coil after heat pump shuts off.

    A better fix would be to insulate the duct work. It probably sweats like crazy in the summer depending on your normal dew point temps.

  5. #5
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    1,976
    It's perfectly normal and here is why...........

    You have the fan set to "ON" or constant circulation. This means that when there is no call for heat the fan is running at whatever speed it's set to in the constant circulation mode. If the air blowing out of the registers is uncomfortable when there isn't a call for heat check with your contractor to see if the speed of the blower can be set lower for constant circulation. A slower air speed usually will not cause as much discomfort.

    Secondly the air that is coming out of the registers is being pulled into the blower from the return ductwork that is connected to your return air registers. "Usually" these return air registers are located near the floor. Cold air sinks and warm air rises. You thermostat (set to 68&#176 is located approximately 5' above these return registers. The air at the floor could be as much as 2° cooler than the air at your thermostat.

    This is all assuming that you verified that the digital thermometer you are using is in complete agreement with your thermostat in telling you what the temperature is.

    Constant circulation is used for many different reasons in homes around the country. Some people use it to filter the air constantly. Some people use it as a "bandaide" to solve larger differences in temperatures between rooms and floors (a poor man's zoning if you will). Others have their system fan running continuously because they have no idea how to shut it off. I even had a few customers run their fan constantly because they couldn't stand the house being quiet.

    You didn't mention why you were measuring temperatures out of the register....... what started this quest for information?
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,722
    Is your duct work in the attic, or unconditioned crawlspace.
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    How-to-apply-for-Professional

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

  7. #7
    Join Date
    Apr 2007
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    6,285
    Quote Originally Posted by beenthere View Post
    Is your duct work in the attic, or unconditioned crawlspace.
    opps......forgot the very first question...and just assumed.

  8. #8
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,134
    Always PREsume.

    Perhaps you should have read the instructions before calling.

  9. #9
    Join Date
    Feb 2007
    Location
    Bellingham, WA
    Posts
    115
    Quote Originally Posted by beenthere View Post
    Is your duct work in the attic, or unconditioned crawlspace.
    My duct work is in a conditioned crawlspace. The furnace is on the 1st floor and pushes the heat down into ducts in the crawl.

  10. #10
    Join Date
    Feb 2007
    Location
    Bellingham, WA
    Posts
    115
    Quote Originally Posted by firecontrol View Post
    You didn't mention why you were measuring temperatures out of the register....... what started this quest for information?
    The temperature in that room is lower than the set point on the thermostat. By keeping the fan on, I am trying to maintain a more uniform temperture in that room. That is why I am on this quest.

  11. #11
    Join Date
    Apr 2007
    Posts
    6,285
    Quote Originally Posted by jechow View Post
    My duct work is in a conditioned crawlspace. The furnace is on the 1st floor and pushes the heat down into ducts in the crawl.
    Conditioned crawl space? You are heating/cooling/dehumidifying/humidifying the crawl space?

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,722
    If the crawlspace doesn't have a supply, its an unconditioned crawlspace.

    Does it have a supply, that keeps it the same temp as the rest of the house.
    Your supply temp from that register in that room, implies that the duct is running through an unconditioned space.
    Contractor locator map

    How-to-apply-for-Professional

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

  13. #13
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    1,976
    Quote Originally Posted by jechow View Post
    The temperature in that room is lower than the set point on the thermostat. By keeping the fan on, I am trying to maintain a more uniform temperture in that room. That is why I am on this quest.
    Is there adequate return air in this room? I'm guessing the room either doesn't have enough return air or large amounts of glass or some other reason it's loosing heat faster on average than the rest of the home.

    You should be seeing higher temperature rise when heating with the heat pump running. What are other registers reading as far as temp when the heat is running. Trace the difference referenced to where the registers are connected to the ductwork. This might show you where you're loosing the heat. If you see 20 rise near the furnace and only the 7-10 at the one you're now measuring, the heat is being lost via the ductwork. Insulating the ductwork will solve this problem and possibly bring the room closer to set point.

    This isn't necessarily the answer, but something to think about.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

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