I have a vision pro 8321 thermostat on a single stage heat pump with a single stage gas furnace backup. Also have external temp sensor. My problem is that when the heat pump can not keep up to the load it allows the house temp to drop 5 degrees before the gas furnace starts. Have called honeywell and tech said this is right and non adjustable,
I find this hard to believe! Must be some special code to get it down to 2 or 3 degrees, 5 is very chilly.
Thanks for any help, ted

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i have a vision pro 8321 thermostat on a single stage heat pump with a single stage gas furnace backup. also have external temp sensor. My problem is that when the heat pump can not keep up to the load it allows the house temp to drop 5 degrees before the gas furnace starts. have called honeywell and tech said this is right and non adjustable,
i find this hard to believe! must be some special code to get it down to 2 or 3 degrees, 5 is very chilly.
thanks for any help, ted


Are you using this setup on page 11? If not I recommend you do to start with since you already have the outside sensor. All details are in the manual in one of the links below.


http://customer.honeywell.com/techlit/pdf/PackedLit/69-1896ES.pdf


Heat Pump Temperature Lockout (with fossil-fuel backup): If the thermostat is installed with an optional outdoor sensor, you can select a compressor lockout temperature (Function 0350). When the outdoor temperature is below the lockout temperature, only the auxiliary heat operates. When the outdoor temperature is above the lockout temperature, only the compressor operates.

Set it up and see if that helps your problem. Post back with results and for other possibilitys.