Programmable thermostat for heat pump with aux heat

Old 01-20-17, 12:04 PM
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Programmable thermostat for heat pump with aux heat

We have a geothermal heat pump and a well insulated house, which means the built in electric aux/emergency heat is NEVER needed, even in sub-zero weather (fifteen years of experience). The manual thermostat has a three-position switch: "Off/Aux/Emerg". It is ALWAYS in the "Off" position (except when I test it once or twice a year).

I'm looking for a programmable thermostat that provides the same level of control - ie, the ability to override the Aux heat function. Not having much luck. Any ideas?
Old 01-21-17, 08:17 AM
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The thermostats to consider might include the Honeywell TH8321R, The Honeywell Prestige IAQ, and the Nest.

The TH8321R will let you increase the difference between the heat strips and compressor demand. Increase it enough and the strips shouldn't come on.

It may give you more control over the strips than this but of the many Geo thermal units that I service every year I can only think of a few that even have heat strips in them. ( It may be able to be configured for emergency heat only but I would need to look into it.)

The Nest will let you connect the strips to the * terminal and configure it for emergency heat. I have done this on a Geo up near Conroe. ( I think my thermometer is still in the air duct behind that unit)
Surfing that stat to turn on the heat strips in this manner is kinda odd.
I have probably only installed two dozen Nest thermostats. This may be why I still don't care for them much. I don't feel like the Nest give me enough control of my system from the stat. It is the only stat of these three that I have installed for your application.

The Prestige IAQ would be (and is) my choice.
The Honeywell Prestige IAQ gives you the most control and allows for the installation of many sensors and HVAC addons like fresh air dampers, humidifiers and dehumidifiers. With the duct sensor package you can check the delta Tee from the stat.

Installation of this control is more involved and Honeywell recommends professional installation. They will not help you install it over the phone.
Old 01-21-17, 11:39 AM
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If never needed you do have the option of just not hooking it up. Other options are to install a separate manual switch or even a second emergency thermostat set to 50 or so. Either of these could be mounted elsewhere such as a laundry/utility room.

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