What is the ideal outside temperature to set for the change between my air source heat pump and oil burning furnace?

Question

What is the ideal outside temperature to set for the change between my air source heat pump and oil burning furnace?

Asked by Gary Marder

I have a Nest thermostat which will change system automatically. I'm in upstate NY and looking for what makes the heat pump most efficient.

Answer this question

Answers

Michael Holcomb's picture

Gary,

A heat pump may be an efficient method of cooling your home in summer and warming it in winter. A heatpump works by moving heat.

  • In the summer, a heat pump operates like a standard electronically drivenair conditioner, collecting heat from the air in your home and expelling it outside.
  • In winter, the process isreversed, and the heat pump collects heat from outdoor air to warm the air inside your home.

Even the coldest winter air contains some heat. However, heat pumps work best at temperatures above35 degrees Fahrenheit (2-degrees Celsius).

Below this temperature, an electrical resistance heaterswitches on (or in your case fuel oil furnace), if required, to supplement heat brought in from outside.

While many people find the winter operation of a heat pump the most difficult understand, it is during theheating cycle that the heat pump produces the most significant savings.

  • Unlike a furnace, that turns fossil fuel or electricity into heat, the heat pump collects heat that alreadyexists in the outdoor air by means of its refrigeration cycle.
  • Consequently, your heat pump will produce2 to 3 times more heat than the energy it uses. The colder it is outdoors the less available heat and thelower the efficiency.

So, in your climate zone I would suggest you set the cutoff at 35-degrees Fahrenheitif the manufacturer hasn't given a different temperature based on their equipment and your climate zone.

For more information:

Read "My apartment has a heat pump. How can I install a thermostat with a timer?" a Q&A answered by Sean Shanley.