Many of the older fractional horsepower refrigeration systems, such as reach-in coolers or prep table coolers, use a mechanical constant cut-in control to regulate the air temperature within the case. This style of control directly measures the temperature of the evaporator coil to control the case temperature and provides a method of defrosting the coil during each off cycle. Each time the control cycles the compressor off, the control will not cycle the compressor back on until the evaporator is void of frost and reaches the desired cut-in temperature of the case.
Today’s newer systems do not use this style of temperature control. Most manufacturers today are designing systems using an electronic temperature controller, which directly senses air temperature. These controllers have many advantages over the older mechanical controls, including the following: