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  1. #1

    Hmm Honeywell Thermostat - Excessively turning to AUX Heat

    Hi all! I am not sure this is an issue or not, but it is really bugging the heck out of me and I really need to know the answer.
    I live in Western PA, it was 17 degrees this morning, going up to around 40 today.
    Using a Honeywell, non programmable digital thermostat
    Main heat is a Concord 90+ High Efficiency Gas furnace converted to Propane (forced air). This system is about 4 maybe 5 years old. Has the air filter.
    In 2011 I added in a heat pump to use as a backup heat in spring and fall (trying to reduce costs on propane use) / AC unit for summer.
    Have been using both for 2 years now… with no issues that I could tell.
    The way the thermostat is hooked up is that HEAT is the heat pump, EMER HEAT is the Gas Furnace.
    The way we use it is: During the fall/spring, if the outside temp is over 45-50 degrees we use the HEAT (aka the heat pump), if the outside temp is UNDER 45-50 degrees we switch over to the EMER Heat (aka Gas Furnace).
    This is fine except this year I noticed the following:
    We went away a few weekend and ran into something I think is odd. When went away for a weekend we turn the heat down (no need to heat an empty place), usually turn in inside temp down to 55 (with the outside temp being so cold lately, we have it on EMER HEAT - aka Gas Furnace). When we arrived back, we turn it back up to around 64-65 - well, here is what I am running into:
    Keep in mind that we have it on EMER HEAT / Gas Furnace: I turn the heat up to 64 the heat kicks on in about a minute, it runs and the Honeywell Thermostat goes from HEAT to AUX Heat. Now I noticed this happening the last 3 times we went away and came back. So this time I decided to turn up the heat slowly. I went from 55 to 57, within a minute of the heat kicking on Honeywell Thermostat goes from HEAT to AUX Heat, I turn it down to 56 and AUX Heat goes back to HEAT. I kick it back up to 57 and it goes back to AUX heat.
    It also, and this may be just me since now I am worried, seems to run the fan more often after the heat kicks off.
    Is this normal, should I be worried. Should I call a repair man?
    Help! Thanks!

  2. #2
    PS this looks like my Digital Thermostate
    Not sure if it is exact, but it gives you a feel of what i am looking at.

  3. #3
    Join Date
    Dec 2007
    Sounds like it is probably normal, I cannot access you link.
    Many lower end thermostats do this when temp is increased by a couple degrees.
    Also, though you did not mention it, there may be controls to keep the heat pump from operating below a certain temp.

  4. #4
    Thank you so much! That makes me feel better! I never noticed it before, I guess I started to second guess it! Thank you again!
    I will also check on the heatpump settings as well.

  5. #5
    Join Date
    Mar 2009
    Mount Holly, NC
    most digital thermostats have a range where they bring in the "aux" heat. but as mentioned, most dual fuel systems have lockouts to prevent the heat pump from running when it's inefficient. and 17°F certainly qualifies for that one!
    the range should be adjustable, so if it's 2F now, you could raise it to 5 or 10F if there is room.
    also, you should not be able to run the heat pump and the gas heat at the same time, damage can occur with the HP getting gas heat dumped on it.
    The TRUE highest cost system is the system not installed properly...

    I am yourmrfixit

  6. #6
    Join Date
    Jan 2009
    Keokuk, IA
    +1, sounds like it's not a proper dual fuel thermostat, which with propane, you really really want. You want to run the heat pump as much as possible, don't change the tmeprature setting except by 1-2 F and only for comfort, and only turn it way down if you'll be gone for more than 2 days. Since you have propane, I would se the heat pump lockout very low, like maybe 5F as mentoned, then the furnace lockout at maybe 25-35F, or whatever temp the heat pump starts to fall behind (depends on your climate and if it was sized properly for cooling, or oversized for heating capacity)

  7. #7
    Join Date
    Jun 2007
    Greenwood Indiana (Indianapolis)
    This is a dual fuel system and you need to have a dual fuel kit. They have all sorts of names, like plus one, fuel master.... You need one for the type of system you are describing or the heat pump will run with the gas furnace which is a no no. Or you can get a thermostat that is made for dual fuel if you don't have a dual fuel kit.
    As iron sharpens iron so one man sharpens another Proverbs 27:17 NIV84

  8. #8
    Join Date
    Jan 2004
    When in emergency heat mode. There isn't any aux heat. Sounds like it wasn't in emergency heat mode.
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