Final answer:
The defrost timer in a frost-free freezer connects to either the compressor or the defrost heater. The compressor increases temperature and pressure, while the condenser coils extract heat. The defrost heater melts any frost or ice on the evaporator coils.
Step-by-step explanation:
In a frost-free freezer, the defrost timer is wired so that at any given time, it connects to either the compressor or the defrost heater.
The compressor is responsible for increasing the temperature and pressure of the gas, which is then forced into the condenser coils to extract heat from the freezer and exhaust it to the outside.
The defrost heater is used to melt any frost or ice that may accumulate on the evaporator coils during the cooling cycle.