The Heat Pump Defrost Cycle Explained


Baggett Heating and Cooling gives you all the important information you need to know when it comes to your heat pump defrost cycle

As colder weather approaches and we start to see freezing temps, your HVAC system will be working hard to defrost itself. It is perfectly normal to hear a strange noise and see steam coming from your unit.

Heat pump defrost cycle

  • Ice begins to form on the heat exchanger of the outdoor unit when outside temperatures reach freezing levels.
  • When this happens, your heat pump enters defrost mode to thaw the ice.
  • This keeps the unit operating at maximum efficiency and prevents damage to the equipment.
  • Here’s a video of what happens when it’s in the defrost cycle. 

How do I know it’s working?

  • If the outdoor temperatures have been freezing for some time, expect the heat pump defrost cycle to begin.
  • The unit will cease blowing warm air into your home during defrosting which may cause you to hear a humming sound.
  • The defrost cycle typically lasts about 10 minutes.
  • The cycle shouldn’t defrost more often than every 30 minutes.

What if it doesn’t stop defrosting?

  • The unit might not be big enough to heat your whole house.
  • You could have a clogged filter. Make sure your filters are cleaned and/or replaced regularly.
  • Clear all leaves and debris from on and around the outside unit to make sure the water from the defrosting cycle can properly drain.

When are problems most likely to occur?

  • The worst time of the year for heat pumps is when it’s snowing.
  • The conditions are already perfect for moisture to freeze on contact on the outdoor coil.
  • The outdoor fan motor pulls air across the outdoor coil and the snow gets drawn into the coil.
  • If your unit has just finished a defrost cycle, there’s probably enough snow in the coil to require another defrost cycle.

Be patient and let your unit do the work.

However, if you do think you have a problem with your HVAC unit it might be time to call Baggett Heating and Cooling. Baggett recommends having regular maintenance performed on your HVAC system. Learn more about regular maintenance and join Baggett’s Preferred Customer Maintenance Club.

Baggett Heating & Cooling has been serving the Clarksville/Montgomery County area for over 40 years. Contact us by phone or email.