Outside temp and heat pump change over

[mohawk43]

We have a new Bryant #286 heat pump hooked up with a natural gas Bryant 90i furnace. We live in the Twin Cities area of Mn and I am wondering what the break point temp would be set at for the furnace to take over the heating from the heat pump. I have called the installers and they thought somewhere in the 20's, but the heat pump was running this morning and it was 11 degrees outside. I don't want to be spending more in electric for the heat pump if it would be cheaper to run the gas furnace. Anybody have an idea here?

[badtlc]

What are the prices for your elec and gas? For me, my economy break even point between my heat pump and 80% gas furnace isn't until -15 degrees F. Typically, you'd want to let your heat pump run as low as it can keep the house up to temperature. At the point the heat pump can no longer maintain temp in the house, that is a good crossover point to lockout the heat pump.

Was your heat pump keeping your house warm at 11 degrees?

[mohawk43]

Yes the house is still warm-68 degrees although it seems to turn on frequently. We pay 0.0877000 per kwh and 0.88128 per thm. I wondering if we're using more power for the electric since it needs extra time after heating to defrost?

[badtlc]

Do you have your COP chart for your heat pump? If so, go here

Warmair.com

Use that with your rates and your efficiency rating of your furnace. Change the COP on electric until the price for gas = electric heat pump. Then find the temperature at which that COP occurs. That will be your crossover point at which you'll want to lockout the heat pump.