What can terminate the defrost cycle in a heat pump system?

In a heat pump system, the defrost cycle is essential for removing frost accumulation on the outdoor coil, which can impair the unit's efficiency and performance. The termination of this cycle primarily relies on either a set duration of time or a specific temperature threshold.

When the system has been in defrost mode for a predetermined amount of time, or if the temperature of the outdoor coil rises above a certain level, the heat pump will cease the defrost cycle. This mechanism is crucial to ensure that the system returns to its normal heating operation promptly to maintain indoor comfort levels.

Choosing time or temperature as the correct answer reflects the systematic conditions under which the defrost cycle is designed to conclude. This approach helps maintain efficiency and protect the heat pump's components from excessive wear or potential damage that could arise from extended defrost operations.