Initiation of defrost in a heat pump system can be done by which of the following methods?

Initiation of defrost in a heat pump system can be done by which of the following methods?

• A. Timed sequence
• B. Temperature
• C. Humidity level
• D. Electronic board

Answer: (B)

Defrost is started because frost forms on the outdoor coil, and the system needs to melt that frost to restore efficiency. The primary cue for triggering defrost is a temperature reading from a sensor on or near the outdoor coil. When the coil temperature drops low enough to indicate icing, the control initiates a defrost cycle, reversing the refrigerant flow to heat the outdoor coil and melt the frost. Some systems may also use a timer to schedule defrosts, but the actual initiation is still driven by the temperature condition, not a humidity reading. Humidity level isn’t a direct trigger, and the electronic board is the worker that carries out the defrost sequence once the temperature condition is met.

Defrost is started because frost forms on the outdoor coil, and the system needs to melt that frost to restore efficiency. The primary cue for triggering defrost is a temperature reading from a sensor on or near the outdoor coil. When the coil temperature drops low enough to indicate icing, the control initiates a defrost cycle, reversing the refrigerant flow to heat the outdoor coil and melt the frost. Some systems may also use a timer to schedule defrosts, but the actual initiation is still driven by the temperature condition, not a humidity reading. Humidity level isn’t a direct trigger, and the electronic board is the worker that carries out the defrost sequence once the temperature condition is met.