"Exterior"

"Exterior" sensor This is a thermistor measuring the air temperature in the entry to the outdoor coil. It controls the operation of the pump, stopping it when the outdoor temperature approaches -15°C. This prevents the compressor from operating at a high ratio, which could damage it. It allows for the switching on of the duct heater (optional) controlled by the 2nd phase of the ambient thermostat, if the exterior temperature drops below -15°C. Through the "balance point", it allows for adjustment of the temperature at which the additional electric heater has to be switched on. "Discharge" sensor This is in the discharge tube from the compressor, installed in series with the high cut-out. It protects the compressor against high operating temperatures. It protects the compressor against high operating pressures. It stops the compressor if the discharge temperature exceeds what is permitted, or if the pressure exceeds 28 kg/cm2 . It protects the compressor if there is a drop in refrigerant charge or a reduction in air flow-rate through the outdoor or indoor coils. It permits resetting the compressor circuit after a lockout