The Energy Saver consists of a Printed Circuit Board containing a power supply, a power relay, control circuitry and a temperature sensor. There are no screw terminals on the PCB. All electrical connections are by means of polarised connector plugs. There is no display on the Energy Saver itself, but all relevant values and settings in the Energy Saver are accessible via a Hand Held Programmer.

The Energy Saver measures temperature and voltage, and uses these two measured variables in conjunction with two other s and its proprietary control algorithms to determine whether to allow compressor operation or not. The two other s are the reversing valve status (on a heat pump unit) and an optional door switch.

When the Energy Saver is first powered up, operation of the compressor is disabled by means of an adjustable Compressor Minimum Off Timer (anti-recycle timer). Only when this timer has counted down to zero will the compressor be enabled to run by means of the compressor relay closing.

During operation, the Energy Saver is constantly measuring the AC supply voltage and the room temperature. After the Compressor Minimum Off Timer has counted down, if these two measured variables are within the required parameters, the compressor relay contacts are closed. A description of the various functions follows.