I have a heat pump with propane auxiliary heat. It has a carrier programmable
Thermostat #960-120032-2.

It was programmed for backup heat to come on at 40 degrees when it was installed and I
Would like to reset it to a lower setting. I have read the manual and it makes no mention
Of this setting or how to adjust it.

Carrier has no such part number available.
Please post correct part number.

The number from my owner's manual is TSTATCCPRH01-B
I hope this helps to identify it.

800-284-8227
Thermostat technical specifications
Amy Sellenriek
Replacement Components Division, Carrier Corporation

Ask Amy about cycle rate and anticipator adjustments and heat pump lock out temperature.
I looked over a electronic diagram of your stat and it does not say. If that is the case after talking to her then you have a fixed setting thermostat and you will not be able to adjust it.

I believe yours might be a series from about 1998 and those adjustments were offered as extra cost to the dealer.

Info on your stat

TSTATCCPRH01-B
Thermidistat Control – Non-Programmable/Programmable Thermostat with Humidity Control. (For use in Dual Fuel,
AC, HP, and 2S applications. Includes Outdoor Air Temperature Sensor

Thanks for your help. I'll give Amy a call.