Final answer:
The most common method of defrosting the outdoor coil on an air source heat pump is by initiating a defrost cycle, which temporarily reverses the system to melt away any frost or ice.
Step-by-step explanation:
The most common method of defrosting the outdoor coil on an air source heat pump is by reversing the operation of the system to initiate a defrost cycle. In this process, the system switches temporarily to air conditioning mode, reversing the flow of refrigerant.
This change causes the outdoor coil (the evaporator in heating mode) to heat up, melting any frost or ice that has accumulated. This defrost cycle is essential for maintaining the heat pump's efficiency, especially in cold weather conditions where ice can build up.
During a typical defrost cycle, the heat pump will stop heating the home momentarily. Instead, it will use its own heat to warm the outdoor coils. The built-up frost melts away, and once the defrost cycle is complete, the heat pump returns to its normal heating operation. The temporary switch to cool the outdoor coil ensures continuous, efficient performance of the heat pump during the colder months.