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  1. #1
    Location of house: white rock B.C. just North of Blaine Wa. Winter design temp 15*F. Summer cooling design temp 79*F.

    Heating/cooling equipment:
    Downflow Natural Gas furnace 66,000 Btu/hr input. 80% efficient. Blower motor D.C. with speed setting DIP switches. Blower set for 950 cfm for heat and cool.

    Heat pump Carrier 38YXA single speed 2 ton capacity. Indoor coil Carrier CD5AXA030014ABAA.

    Carrier heat pump programmable thermostat.

    Thermostat located in "warm" hallway. Offset adjustment set at -2*C (-3.6*F) to give 20*C (68*F) in most of the house.
    QUESTION: Does the offset affect settings such as balance point or auxilliary heat lockout?

    Balance point set at 4*C (40*F) and Auxilliary heat lockout set at 10*C (50*F).

    Defrost timer setting changed from factory setting of 90 minutes to 30 minutes.

    Any general comments on setup would be appreciated.

    SPECIFIC QUESTION ON DEFROST TIMER: With a high balance point, no evidence of frost on outdoor unit. Would it be worthwhile to raise the defrost time to 90 or 120 minutes to reduce wear on reversing valve?

  2. #2
    Join Date
    Nov 2001
    Posts
    1,874
    Just because you have your defrost time set at 30 minutes.
    That doesn't mean it will really defrost every 30 minutes.
    And the same said for setting it at 120. That just means that it will check to see if it needs to defrost at those times. Your reversing valve won't get worn out.

    The defrost times should be set for the best suitable times in your area, I don't know about your climate.
    But I don't think you need it every 30 minutes.
    Did you switch it or is that were the installer set it?
    If you try to fail, and succeed.
    Which have you done ?



  3. #3
    The installer set it at 30 minutes.

    The climate here is mild with lots of rain in the winter at the balance point setting for the heat pump.

    thanks for the response.

  4. #4
    Join Date
    Apr 2004
    Posts
    7,680
    I would have a problem with having a 3.6 degree offset no matter what, but it isnt a furnace problem but a distribution or insulation problem if your halway is 3.6 deg f higher than the rooms

  5. #5
    Originally posted by docholiday
    I would have a problem with having a 3.6 degree offset no matter what, but it isnt a furnace problem but a distribution or insulation problem if your halway is 3.6 deg f higher than the rooms
    While there was no heat being produced, I placed a thermometer on top of the heat pump thermostat for a couple of minutes and repeated the operation with the same thermometer on the fireplace thermostat in the family room. The thermometer registered the same reading (70*F)in both cases while the thermostats registered 68*F in both cases.

    The hallway and family room are at the same temp.

    a case of miscalibrated thermostats?

    Thanks for the comments


  6. #6
    Join Date
    Nov 2004
    Location
    kamloops bc
    Posts
    62

    When was the last time you checked yout thermometer against a anouther techs?

  7. #7
    Join Date
    Nov 2004
    Location
    kamloops bc
    Posts
    62
    Deme
    Hey I'm just up the road from you in Kamloops. Can you give me a call on my cell 250-214-0145 tonight?
    Thanks Steve

  8. #8
    Join Date
    Apr 2004
    Posts
    7,680
    I was under the impression that your offset was an effort to compensate for the drastic temperature difference between the rooms. Your little test has proven that there is no significant difference. So why the offset then?

    So whats the problem?

    With a changoever set at 40 degrees, your unit will be lucky to ever have the opportunity to even go into a defrost. Your system sounds fine to me.

  9. #9
    Join Date
    Feb 2005
    Location
    Central Alabama
    Posts
    466
    If your defrost is leaving a ice ring on the bottom
    you should shorten the defrost time otherwise you can go to 60, 90 mins

  10. #10
    Originally posted by ac in bc

    When was the last time you checked yout thermometer against a anouther techs?
    Thermometer accuracy is not important. If it has an error, the error will be the same for both locations.

    The important thing is that both thermostat readings are the same with the thermometers reading the same (but not necessarily the same as the thermostats).

    Ultimately, it's the old body which tells you whether the temp is ok.

    Thanks for the comment.

    [Edited by deme on 02-04-2005 at 01:40 PM]

  11. #11
    Originally posted by docholiday
    I was under the impression that your offset was an effort to compensate for the drastic temperature difference between the rooms. Your little test has proven that there is no significant difference. So why the offset then?

    So whats the problem?

    With a changoever set at 40 degrees, your unit will be lucky to ever have the opportunity to even go into a defrost. Your system sounds fine to me.
    The wife said the house was cold and I assumed that the hallway was warmer than other parts of the house Furnace sits on the other side of the thermostat wall).

    By changing the offset on the thermostat which controls the heat pump I seem to have solved the problem. Another indication is that now, the thermostat controlled fireplace in the family room hardly ever fires up.

    I found the comments helpful in clearing up the cobwebs in my head. Thanks.

    [Edited by deme on 02-04-2005 at 01:42 PM]

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