Do Heat Pumps Freeze Up in Winter?
In short, no. Heat pumps won’t “freeze up” during the winter months. Despite freezing temperatures outside, an air source heat pump can still transfer heat from the air when it’s below zero degrees. However, air source heat pumps can experience icing during the winter— this is normal because water vapour in the air freezes when it comes into contact with a cold surface.
There’s Ice/Snow on my Heat Pump! What’s up?
Because heat pumps are located outside, it’s normal for them to get covered in snow and ice during winter. Snow resting on top of the unit is nothing to worry about.
Heat pumps use a refrigerant to draw heat from the air, ground or water. If moisture is present in that air and freezes around the unit, it can cause ice buildup.
However, if you see that the unit is covered in ice as well as inside of the coil, there could be a problem other than cold weather affecting it.
To prevent the ice buildup from causing damage, a heat pump will have a defrost cycle. The defrosting function usually kicks in automatically and will keep the coils from freezing over. However, there could be something preventing the pump from running this cycle, such as low refrigerant levels or a broken thermostat/sensor.
Leaves or other debris blocking the vents could also be the issue.
If the drain from a heat pump is blocked or iced over, it can cause water to collect in the bottom of the unit and also cause water to freeze on the unit. For this reason, most manufacturers install a trace heater at floor level.
Additionally, it’s important to consider the area around your heat pump, as it needs free airflow. Putting a bin near it or a fence around it could obstruct its intake and cause problems—you should check manufacturer guidelines and with your installer for minimum clearance distances from walls/objects when installing.
Finally, if the sensor on your heat pump is faulty, it may not be able to detect that ice has built up—and this could explain why the defrost cycle isn’t activating.
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