Defrosting happens when the temperature outside gets too cold, or if there is ice and the system cannot use the heat pump (if your system has a heat pump). To get rid of frost, the system will run a mode similar to the AC to take the heat from inside the house across the indoor coil and transfer it outside to warm the outdoor unit. The goal is to heat the outdoor unit to evaporate the water.
For more information or a visual representation of steps please reference our user guide here
