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  1. #1

    Frequent AUX Heat on with Honeywell IAQ

    Hello,

    I have a brand new Lennox XP15 heat pump, an oil furnace and a Honeywell IAQ thermostat. The thermostat is set to lockout the furnace if the outdoor temperature is above -4 degrees celsius (25 f). This seems to be working fine. The question I have relates to when the temp drops below -4 c. I notice that the second the heat comes on, the thermostat reads "AUX Heat On." This will run for a couple of minutes and the word "AUX" disappears and only "Heat On" remains as the heat pump has taken back over. This also sounds fine to me, except the problem is EVERY time the heat comes on, even if it is just a few moments after it has shut off (this happens when it is REALLY cold outside even if indoor temp shows no change), the thermostat reads "AUX heat on" and then eases into plain "Heat on." Is the AUX part supposed to kick in every time the heat comes on when the outdoor temp is below -4 c?

    Thanks for your help.
    Last edited by weaselmtl; 11-26-2008 at 11:25 PM.

  2. #2
    Join Date
    Nov 2008
    Location
    Meriden, Kansas
    Posts
    435
    Doesn't sound right to me, the way we set them up, once the temp is below the set point (in this case -4c) the heat pump stays locked out and can not run at all until the temp rises above the set point.

  3. #3
    I think the goal is to allow us to use the heat pump as much as possible until the outdoor temp hits -12c. I live in Montreal and the Hydro company has a dual energy meter that forces the switch to AUX heat at -12c regardless of how the heat pump is keeping up.

  4. #4
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    Nov 2008
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    Meriden, Kansas
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    435
    Quote Originally Posted by weaselmtl View Post
    I think the goal is to allow us to use the heat pump as much as possible until the outdoor temp hits -12c. I live in Montreal and the Hydro company has a dual energy meter that forces the switch to AUX heat at -12c regardless of how the heat pump is keeping up.
    In that case we would normally set the lock out at -12c. above that temperature your heat pump would always come on first on a call for heat. If the with the heat pump running the indoor temperature continued to drop then the thermostat would switch to your aux (fossil fuel) heat. Idealy we would keep the heat pump running but normally the fossil fuel furnace and the heat pump cannot be run at the same time because of system design limitations.

  5. #5
    Join Date
    Dec 2006
    Location
    Middle Tennessee
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    *

    Quote Originally Posted by weaselmtl View Post
    The thermostat is set to lockout the furnace if the outdoor temperature is above -4 degrees celsius (25 f)." Is the AUX part supposed to kick in every time the heat comes on when the outdoor temp is below -4 c?Thanks for your help.

    the way you have it set the answer is "yes"



    .
    Last edited by Airmechanical; 11-27-2008 at 10:35 AM.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Quote Originally Posted by weaselmtl View Post
    I think the goal is to allow us to use the heat pump as much as possible until the outdoor temp hits -12c. I live in Montreal and the Hydro company has a dual energy meter that forces the switch to AUX heat at -12c regardless of how the heat pump is keeping up.
    Could be that energy meter causing the problem.
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  7. #7
    Quote Originally Posted by Airmechanical View Post
    the way you have it set the answer is "yes"



    .
    Thanks for your replies everyone. The hydro bi-energy meter for the -12c switch has not been installed yet so that can't be the problem for now (should be installed next week).

    If that is the way I have it set Airmechanical, what settings need to be changed to prevent the AUX from engaging so frequently. Thanks.

  8. #8
    Join Date
    Dec 2006
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    Middle Tennessee
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    Quote Originally Posted by weaselmtl View Post
    what settings need to be changed to prevent the AUX from engaging so frequently. Thanks.

    change the compressor lockout setting to a lower temperature!



    .

  9. #9
    Join Date
    Jul 2008
    Location
    Dutchess County, NY
    Posts
    152
    I think you should lower the Auxiliary lockout temp

  10. #10
    Thanks for the info guys. I adjusted the lockout tems. These are my current settings in the IAQ thermostat. Anything stand out to you that should be changed?

    Also, based on these settings is it safe to assume that AUX heat will come on every time (prior to kicking in the heat pump) there is a demand for heat between -4c and 12c?

    Thanks

    172: 2
    174: 1
    176: 1
    190: 0
    200: 1
    210: 0
    220: 3
    240: 3
    280: 1
    300: 0
    320: 1
    330: 2
    340: 0
    342: 1
    345: 2
    346: 60
    350: -12c
    360: -4c
    365: 0
    370: 1
    372: 3
    374: 1
    379: 0
    400: 0
    500: 10
    502: 0
    510: E
    520: E
    530: 1
    540: 2
    580: 5
    600: 32c
    610: 15.5c
    640: 12
    650: 60
    660: 60
    670: 0
    680: 2
    690: 2
    700: 0.0
    701: 0
    710: 0

  11. #11
    Join Date
    Jul 2008
    Location
    Dutchess County, NY
    Posts
    152
    you really do not want your aux heat to kick on unless it really needs to...hence the term Auxiliary. your heat pump is your primary heat source to a certain temp. ... when you set your aux lockout you are telling it not to come on unless it is under your set point... the compressor lockout temp tells the compressor not to come on when the outdoor temp falls below your set point. so if you set your aux lockout at 40* your aux heat source will not come on until 39* and your heat pump will do all of the heating... now when the temp is below your setpoint and the heat comes on the heat pump should come on first then after a few minutes you should see the aux kick in...then once the aux heat brings the zone to temp the next cycle of heat should bring the heat pump on unless the outdoor temp is below your compressor lockout temp setpoint.. at which point then your aux will be the primary source until the temp rises above the compressor lockout setpoint plus any added droop degrees... for instance; your compressor lockout is set at 20* and your droop was set at 5* your heat pump will not come on untill you have an outdoor temp of 25* ..... hope this helped

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Your settings look fine.

    No, as long as the temp is above HP lock out, it should start with the HP first.
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