Heat pumps can ice up when it is frigid outside and have a certain frost covering them.
While some ice is normal, something is wrong if the entire unit is encased in ice and frozen solid.
What to Check When a Heat Pump is Freezing Up
- Check if the air filter is dirty and replace it. Airflow is a must for a heat pump to work correctly.
- Does any air blow from the vents at all? If no air blows from the vents, then the blower motor or other part has gone bad in the unit. A quick way to test this is to manually set the thermostat to the fan and see if any air blows from the vents.
- When a heat pump runs, the large fan on the outdoor unit (called the condensing fan motor) should kick on at some point and blow air out through the outside unit fins.
- Check the outside unit fins for any debris that may be blocking air from passing through, such as dirt or leaves.
While Heat pumps are becoming much more efficient every year, they each have a set low temperature which they can work and not freeze up.
If the temperature becomes too cold, a heat pump will temporally go into defrost mode to melt the ice.
Defrost mode switches the heat pump into air conditioning mode (yes, air conditioning) for a short time until it unfreezes itself and can go back into heat mode.
Defrost mode usually last only 10-15 minutes. While a unit is in defrost mode, supplemental heat, usually heat strips, kick on to keep the air warm.
Heat strips are large elements that work like a big space heater by using electricity to heat the elements up and send out heat.
Heating a home with heat strips is terribly inefficient and not designed to be on for long periods. If they are used a lot, then it will show up on an electricity bill.
The outside unit on a heat pump will freeze up if the temperature is too cold.
How efficient the unit is, will depend how low a temperature it can work, without icing up.
Some heat pumps are designed to work in very cold temperatures, while others not so much.
A water hose can be used to melt the ice buildup if needed, but don’t use salt or any other abrasive as this will only cause corrosion of the unit.
If the unit is frozen solid but still blowing hot air more than likely the heat strips have activated and are heating the home.
This will quickly run up an electricity bill and be expensive if done long term. A day or two may not be that bad, but weeks or a whole month of heating this way will definitely be noticeable. If this is the case Call out a repairman as soon as possible.