How does the defrost cycle function in a heat pump?

The defrost cycle in a heat pump is essential for maintaining efficiency when outdoor temperatures are low, and frost begins to build up on the outdoor coil. In this cycle, the heat pump temporarily reverses the refrigeration process to melt any accumulated ice or frost. During this reversal, the outdoor coil becomes the heating element, allowing warm refrigerant to flow through it. This heat raises the temperature of the coil, effectively melting the frost and ensuring that airflow is unobstructed and the system can continue to operate efficiently.

Reversing the cycle is crucial because simply turning off the heat pump would lead to continued frost build-up, reducing efficiency and potentially causing damage. Increasing the heating output or cleaning the outdoor condenser are not the primary functions of the defrost cycle. Instead, the main goal is to quickly remove ice, allowing the heat pump to resume normal operation and maintain heating performance. Thus, the answer that describes this critical process accurately is the one that indicates the function of temporarily reversing the refrigeration cycle.