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-   -   Heat Pump But Aux Heat Not Working (https://www.askmehelpdesk.com/showthread.php?t=295514)

  • Dec 24, 2008, 05:13 PM
    davidpwhite
    Heat Pump But Aux Heat Not Working
    Hello. I have a relatively new house (2.5 years) that has an American Standard Heat Pump (2a6b3018-060a1000a). It also has some form of American Standard aux heater (bayhtr?? ) in the air handler. This is controlled by a Panasonic TH8000 thermostat.

    We have had a long period of cold weather here in Seattle and I have noticed that during this time two unusual behaviors are happening with my heating system:

    (a) I have not see the AUX Heat indicator come on on the TH8000 thermostat. I have seen this frequently before and I took it to mean that the aux heater was helping the heat pump along. But I have not seen it at all in at least a week and I have looked frequently at the thermostat.

    (b) There are times when the heat pump is not operating (I can see the fan blades stopped) but there is significant cool air (not icy cold but certainly not warm) coming out of my heating ducts. It is clearly being blown by a circulating fan in the system but there is no warmth.

    I have looked as much as I can at the heating unit under the house and see nothing unusual. I checked the electronic air filter and it seems fine.

    Any idea what may be wrong here? Thanks.
  • Dec 24, 2008, 05:26 PM
    KC13

    Seattle is way too far away for me to see what's going on from here... sounds like the auxiliary heat is not functioning as intended, and this problem is even more noticeable when the system defrosts (cold blow indoors). Forecast: professional help required.
  • Dec 24, 2008, 05:31 PM
    davidpwhite
    Quote:

    Originally Posted by KC13 View Post
    Seattle is way too far away for me to see what's going on from here...sounds like the auxiliary heat is not functioning as intended, and this problem is even more noticeable when the system defrosts (cold blow indoors). Forecast: professional help required.

    That is my thinking too. Luckily I still have the heat pump working to provide some heat.

    Can you tell me what defrosting is going on? I am pretty new to this heat pump thing and would really like to understand it more. Thanks.
  • Dec 24, 2008, 05:37 PM
    KC13

    Defrost will occur periodically as needed. The outdoor unit will shift to the cooling mode and outdoor fan stops while the auxiliary heat is activated to eliminate "cold blow" indoors. Defrost usually lasts 3-10 minutes and steam may emit from outdoor unit - this is normal, don't call the fire department. When very cold outside, the heat pump will occasionally require some "help" from the auxiliary. The observations you have posted suggest that the auxiliary is not functioning.
  • Dec 24, 2008, 05:56 PM
    KC13

    Try this: set the thermostat system selector to the emergency mode and turn the temperature up a few degrees. Does the system blow warm air after a few minutes?
  • Dec 24, 2008, 06:02 PM
    davidpwhite
    Quote:

    Originally Posted by KC13 View Post
    Try this: set the thermostat system selector to the emergency mode and turn the temperature up a few degrees. Does the system blow warm air after a few minutes?

    Thanks for the idea. I have done that and:

    (a) I am feeling hot air come out of the vents

    (b) The aux heat indicator is visible on the thermostat

    So, what does this tell you?
  • Dec 24, 2008, 06:10 PM
    KC13

    There is a system control issue. While not likely to be serious, will still require a pro with heat pump system experience. My suspects in descending order of probable guilt: 1) low voltage wiring. 2) defrost control. 3) thermostat. P.S. Say hi to Frasier for me...
  • Dec 24, 2008, 06:17 PM
    davidpwhite
    Quote:

    Originally Posted by KC13 View Post
    There is a system control issue. While not likely to be serious, will still require a pro with heat pump system experience. My suspects in descending order of probable guilt: 1) low voltage wiring. 2) defrost control. 3) thermostat. P.S. Say hi to Frasier for me...

    Thanks for all your help. I will definitely call in a specialist. I have turned off the emergency heat mode. Was that the correct thing to do? Happy Holidays to you.
  • Dec 24, 2008, 06:21 PM
    KC13

    While not as economical, the emergency mode may be a better choice for now.
  • Dec 25, 2008, 10:02 AM
    davidpwhite
    Quote:

    Originally Posted by KC13 View Post
    While not as economical, the emergency mode may be a better choice for now.

    Thanks once again for your response. I found some info on the internet here Heating, Air Conditioning, Fridge, HVAC: Heat pump thermostat control, thermostat control, heater elements
    And here Previous Question Index: Topics Starting with a
    That made me start checking things more carefully.

    When this cold spell hit, I raised the temperatures on my thermostat schedules. I have never done this before. Under the previous schedule, I had simply raised the temp manually on the thermostat to what I wanted when needed. Thinking back, this is when I typically saw the aux heat indicator show on the thermostat.

    So I just manually raised the temperature from its current setting by a couple degrees and indeed the thermostat does show the aux heat indicator. For this reason, I am thinking that the aux heater does, in fact, work.

    However, I am not sure about if it is working during the defrost cycle of the heat pump. I only found out recently that there was such a thing. I may never have noticed it before because it has never been this cold this long since I have been in this house with the heat pump. Maybe the heat pump only has to go through a defrost cycle when it is very cold. Or maybe it does it frequently but I have only noticed it now because the air being used right now is so very cold.

    It has been suggested that one reason I am not seeing the aux heat indicator as frequently as before is that my Honeywell TH8000 thermostat is in recovery mode (which I have in fact seen for the first time since changing my schedules) and when in this mode, it may not ever call upon the aux heater. But I don't know if this will impact the use of aux heat during defrost or not.

    Thanks for your time and responses. Happy holidays.
  • Dec 25, 2008, 11:00 AM
    KC13
    Considering this new bit of info, the scenario you describe is plausible. Adaptive recovery is intended to provide a more gradual and economical recovery, minimizing or avoiding the need for auxiliary heat. While this new "evidence" is an aquittal for the thermostat, the cold blow periods suggest something is still awry. My top 2 suspects remain...
  • Dec 25, 2008, 11:59 AM
    davidpwhite
    Quote:

    Originally Posted by KC13 View Post
    Considering this new bit of info, the scenario you describe is plausible. Adaptive recovery is intended to provide a more gradual and economical recovery, minimizing or avoiding the need for auxiliary heat. While this new "evidence" is an aquittal for the thermostat, the cold blow periods suggest something is still awry. My top 2 suspects remain...

    Thanks for all the help. I am thinking just as you are. At least I am not worried that things are really awry now. But I am sure I will need professional help to check out the top two suspects. I am starting to wonder if my heat pump is simply NOT wired to trigger the aux heater on defrost. And I just never noticed this until now with the snow and cold weather and me snow-bound stuck at home.

    Thanks to all and happy holidays.

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