Author Topic: Aux heat running with slight increase in temp selection  (Read 1293 times)

Offline Hearttx

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Aux heat running with slight increase in temp selection
« on: December 02, 2018, 06:50:02 PM »
Hi. I have an older Trane heat pump (2009) that runs well but my issue is when I select 1 degree higher in heat mode the system kicks on the aux heat. I have noticed over the last 2 years that the aux heat was coming on more and more often. I had a tech to look at it and he said I need a new thermostat with an outside air temperature sensor. The problem is that it never had an outside air temperature sensor and now all of a sudden I need one. I feel like he is just making a work around and not addressing the problem( which could still be just the thermostat) He was not a Trane certified repairman so I am sceptical of his solution.  I thought about buying a replacement myself and installing but dont want to pull the trigger on a new stat if that is possibly not the issues. So what are your thoughts on this? TIA!

Offline Admin

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Re: Aux heat running with slight increase in temp selection
« Reply #1 on: December 02, 2018, 07:05:59 PM »
I would trust in their warranty.  It could be a control issuse which is cheaper than having a refrigerant leak problem.  Usually there’s an outdoor sensor so when it’s too cold outside the heat pump will stop running and only aux heating will be used.

What model of thermostat is it?


Offline Hearttx

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Re: Aux heat running with slight increase in temp selection
« Reply #2 on: December 03, 2018, 07:43:41 PM »
It is a tcont802as32daa.

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Re: Aux heat running with slight increase in temp selection
« Reply #3 on: December 03, 2018, 08:41:33 PM »
Did he put guages on the unit and check the refrigerant charge?

Press the FILTER/OD button to see if an outdoor sensor is installed.

Quote
Outdoor Temperature Sensor
With the outdoor sensor installed and enabled, outdoor temperature can be displayed on the Comfort Controls display by simply pressing the Filter/OD button. Also, the outdoor sensor is required for the following control features: Cooling Efficiency Booster, Heat Pump Restricted Mode, Heating Aggressive Recovery, Auxiliary Heat Lockout, and Defrost Heater Balance Point control.

If it displays the outdoor temperature is it accurate?

To enter the installer menu,
1. Set System MODE to OFF
2. Set FAN to AUTO
3. Press and hold MODE and Up arrow at the same time.

Check option 43 - Heat Pump Restricted Mode Outdoor Temperature.  The heat pump will run anytime the outdoor temperature is above this number.

Check option 46 - Auxilliary Heat Lockout.  The AUX heat will not run anytime the outdoor temperature is above this number, unless the heat pump is in defrost mode.  There is an aggressive recovery mode but that should only start the AUX heat when the the thermostat is raised more than 2 degrees.  Check options 35 and 45.

Are you using a setback program and dropping the temperature at certain times of the day?  Did you change any settings in the thermostat?

Without an outdoor sensor I’m not really sure how the system operates as a dual fuel system.  Is the AUX heating system gas or electric?

Offline Hearttx

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Re: Aux heat running with slight increase in temp selection
« Reply #4 on: December 05, 2018, 06:15:22 AM »
Thank you for your response. I dont believe he checked the pressures. He said the unit looked good and seemed to be going on the thought that the thermostat was bad and concentrated on that. I went into the installer setup but there are no option 43 or 46. The lowest option number is 0120. I had in the past set it to show OAT but it came up with no reading and I guess confirmed when he said I needed to install an OAT sensor as well as a new stat. We do not use the setback option. My understanding was it is better to leave it at one temp and make small manual adjustments as required.

Offline Hearttx

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Re: Aux heat running with slight increase in temp selection
« Reply #5 on: December 05, 2018, 06:17:51 AM »
Oh and the secondary heat is electric.

Offline Hearttx

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Re: Aux heat running with slight increase in temp selection
« Reply #6 on: December 05, 2018, 06:36:42 AM »
I went online and found the installer codes for the stat and went through to see what my settings are compared to what the manual says and the only option I found off was the second stage cycles per hour selection was set to fossil fuel and not electric. I changed that option to electric so maybe that helps.