A frozen home heat pump is bad news, but there are several easy strategies to safely unfreeze your heat pump with minimal tools and time. This is definitely a simple job for any DIYer.
Step 1 - Understand the Problem
Frost can occur at temperatures 40 degrees Fahrenheit or lower, and any time that frost can occur, your heat pump can ice up. Whether your heat pump is creating cold air to ward off excessive heat, or trying to warm up your house when it's frosty outside, some ice buildup is inevitable. To prevent excessive buildup of ice, most home heat pumps use a timed, temperature-based defrost system.
This system runs on a timer composed of either a motorized clock or an electronic timer, and the timer is set to defrost your system at intervals that vary based upon the manufacturer and heat pump model, though the most common timer settings are 30, 60, and 90 minutes. Many commercial systems also have a pressure switch installed that can sense when the coils have been jammed with ice. Unfortunately, this feature is rare in residential applications, which increases the likelihood of troublesome ice buildup in your home heat pump.
Step 2 – Run the Fan
The simplest solution, in the temporary sense, is sometimes the best place to start. If it is warm outside, try turning on the fan; usually, the blowing air will thaw the heat pump within an hour or so. If it is cold outside, try the same option on an exhaust setting, if one is available. Running the fan will not help with recurrent freezing issues, but it's a good start to getting your heat pump up and running.
Step 3 – Move the Sensor
Your heat pump needs to defrost frequently when frost conditions occur, and the defrost needs to last long enough to eliminate the ice, but not so long as to waste electricity. Sometimes moving the temperature sensor or thermostat on the outdoor portion of the unit will correct the problem. Nearest the intake area is usually the best position. If you try relocating the sensor, make sure to mark the original location. Otherwise, if the new location works out to be worse than the original, you may not be able to properly replace it, in which case you'll have many hours of trial and error ahead of you. Placing the thermostat at the wrong end of the coil will also stop all defrosting, the opposite of the desired result.
Step 4 – Manual Defrost
If your unit has a manual defrost option, run it whenever the conditions usually cause freezing. The power-saving settings on your heat pump may save you money on electricity, but unfortunately, they may also be the reason for your frosting issue. A too-short defrost cycle can cause freezing, and ultimately a hassle for the system owner. Make sure that your system is set up as close to the manufacturer's specifications as possible for proper clearance and ventilation.