Abstract: A refrigeration system provides one or more compressors, a condenser, and a plurality of evaporator coils fed with the liquid refrigerant from the condenser. Each coil is disposed in a chamber to be held at a particular low temperature by blowing air over the coil as liquid refrigerant in the coil evaporates to gas, with the absorption of heat. Each coil returns gas refrigerant back to the compressor(s) through an individual gas return line. A temperature sensor in each chamber provides an output signal related to the temperature provided by the coil. A controller receives each output signal. An on/off valve in each gas return line is controlled by the controller in response to the sensor signal to stop refrigerant flow through its respective coil when the temperature goes below a preset level and allows refrigerant flow when temperature is above a preset value. The on/off valve may be part of a conventional evaporator pressure regulator in which the regulator is adjusted wide open.