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mranswer, HVAC Mechanic
Category: HVAC
Satisfied Customers: 6160
Experience:  20 years experience running my own business
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At what temperature should a heat pump switch to auxiliary

Resolved Question:

At what temperature should a heat pump switch to auxiliary heat (in my case, oil boiler for baseboard radiator heat? The boiler is currently turning on at 47 degrees.


Submitted: 5 years ago.
Category: HVAC
Expert:  mranswer replied 5 years ago.
Usually somewhere in the low 40s is a good spot. Much below that and there simply is not enough heat in the air to make running the heat pump economical as it is using more power to run than the 'power' of the heat it can transfer into the house.
Customer: replied 5 years ago.
Does that also apply if the auxialiary heat comes from strip heaters inside a heat pump? When I lived in a townhouse that had strip heaters for auxiliary heat, I don't recall them coming on (blue emergency light on thermostat) when it was in the 40's.
Expert:  mranswer replied 5 years ago.
It makes no difference what your other heat source is inside-the same physics apply to the heat that the heat pump can generate. The emergency heat light does not light up unless you set it for such mode and the aux heaters usually kick in whenever the temperature is needed to increase by more than 2 degrees- like when you push up the t/stat to get the place warm upon waking, etc.
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