One of the most misunderstood parts of operating a heat pump is the defrost mode. Discover what the defrost cycle is, when it turns on, and if it should concern you when it’s active.

What Is Defrost Mode?

Defrost mode is exactly what it sounds like: a mode that defrosts your system. Specifically, it focuses on the coils in the outside unit. It detects when these get cold enough to allow frost to form on the coil, which can damage the coil.

When the defrost mode initiates, it triggers the reversing valve, taking the system out of heating mode and putting it into cooling mode. This effectively pushes hot refrigerant into the outside coils to warm them up and melt any frost buildup. This cycle generally lasts up to about 15 minutes.

Why Does Defrost Mode Start?

As already stated, defrost mode starts when the coils get cold enough to form frost. Frost happens because of two phenomena happening simultaneously. The coil has to be both cold enough to condense moisture from the surrounding air and cold enough to freeze it.

To absorb heat from the air outside and bring it in, the outside coil must be colder than the air temperature. This temperature drop happens as a byproduct of compressing a refrigerant and can happen at most outdoor air temperatures.

If the fan is not working well enough to clear away frost-forming moisture or air is particularly cold, the defrost cycles may increase in frequency. This is when you may wish to call an HVAC professional to troubleshoot.

Should Defrost Mode Concern You?

Defrost mode is usually not something that should cause much concern. However, if it’s running during warmer temperatures, such as above 40 degrees, or for extended periods, you may have a problem. Some problems cause the coils to get too cold, such as a refrigerant leak or a malfunctioning compressor. A qualified HVAC technician can easily diagnose problems that will cause the heat pump to get too cold or trigger the defrost mode.

For more than 20 years, people around Prescott Valley have turned to Moyer’s Heating & Cooling Inc. to keep their homes comfortable. Our team provides AC and heating maintenance, installation, and service combined with indoor air quality solutions. Call today to schedule your heat pump repair with one of our NATE-certified technicians.

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