Understanding Heat Pumps

heat pump graphicHeat Pump 101

  • Sometimes referred to as a central heating and cooling unit because it warms your home in the winter and cools it in the summer.
  • In cold weather, it collects heat from the air outside and concentrates it for use indoors. In warm weather, it collects cool air from outside.
  • The heat pump has two main components:
    1. Outdoor unit (compressor): The compressor uses a refrigeration cycle and, when operating, is where energy efficiency is found. 
    2. Indoor unit (air handler): The air handler is an electric forced air furnace that has a connection to the outdoor unit’s refrigeration lines as the primary heating/cooling system.
  • Duct work is connected to the air handler that has a large fan to blow air across the refrigeration coils or the backup heat’s electric coils. This distributes heated air throughout your house during the winter.

What is the backup heat and what causes it to come on?

  • The alternate form of heat is sometimes referred as “strip heat”, “aux heat”, or “backup heat”.
  • You can usually see when it is on by looking at your thermostat.
  • When it gets too cold outside, the heat pump can’t extract heat as normal from the outside air temperature. To heat your home, the electric coils are turned on, and is referred to as backup heat or “strip heat”.
  • If the backup heat comes on, the electric coils are energized.
  • This is a very inefficient way to heat air. It uses more electricity and costs more money.
  • If your thermostat calls for heat greater than about two degrees, the backup heat turns on and works with the heat pump to boost temperatures more quickly.
  • If your heat pump is not working properly, backup heat will become the primary heat source, and can be costly. 

Tips on how to reduce how long backup heat runs in the winter

  • Before winter comes, have your heat pump serviced by a licensed HVAC technician.
  • Make sure your home is well insulated.
  • Check your thermostat. If you need to warm up your house, slowly ramp up the temperature over the course of an hour. The slow ramp up will allow your heat pump to increase the temperature in the house, without relying on the electric coils for assistance.
  • Make sure the ductwork is in good repair. 

Heat Pump Terms:

  • SEER – Seasonal Energy Efficiency Ratio: This is an efficiency term relative to cooling. The higher the SEER, the lower the operating costs. For example, a 13 SEER unit costs less to operate than a 10 SEER unit.
  • HSPF – Heating Season Performance Factor: An energy term relative to heating. The higher the HSPF, the lower the operating costs. For example, an 8.2 HSPF rated heat pump costs less to operate than a 7.5 HSPF unit.
  • BTU – British Thermal Unit: A BTU is relative to the size of the heat pump unit. The capacity of a heat pump is rated in BTUs, and there are 12,000 BTUs per ton. So, if you have a two-ton heat pump, it has the capacity to produce 24,000 BTUs of heating or cooling.

What to do if your heat pump unit goes out:

  • Check thermostat setting
  • Check filter
  • Check outdoor unit (some have a manual reset pressure switch)
  • Check breakers in main electrical panel
  • If needed, contact a professional HVAC service company