In winter, it’s normal for a heat pump in “heat mode” to be covered in a light frost.
To counter this, your heat pump should periodically go into a brief “defrost mode” to get rid of the frost.
So there’s nothing to worry about.
BUT if the frost isn’t disappearing after an hour or two and the outdoor unit becomes completely iced over, then you have a problem—and you need a professional to repair the system.
In a defrost cycle, the heat pump will use the reversing valve to reverse the flow of refrigerant and go into refrigeration mode—yes the way it typically cools your home in the summer. This causes the refrigerant in the outside unit to heat up and melt away the ice.
If the reversing valve sticks and can’t reverse the flow of refrigerant, it can’t melt the ice.
In this case, you have a refrigerant leak that needs fixing.
Anything from a bad defrost timer, bad defrost thermostat or sensor, or bad defrost relay will prevent the heat pump from defrosting.
The condensing fan keeps cold air from hindering the defrosting process. But, obviously, if the motor is bad, it can’t do that.
If your heat pump is iced up and you have no heat, set your heat pump’s thermostat to “emergency heat.”
This will turn on the backup heating unit (usually an electric resistance coil) that will keep you warm while you call a professional for help.
And, no, you don’t want to keep it set on emergency heat to avoid calling a repair person for help. The electric resistance coil is a monstrous energy hog; it’ll run up your heating bill before you know it!
Do you live in the Phoenix area and need help? Contact George Brazil to schedule heat pump repair.