A refrigeration system comprising: a compressor having a suction and a discharge; a heat rejecting heat exchanger; an expansion valve; a heat accepting heat exchanger; a pressure equalisation valve (40,42) for equalising the pressure differential between the compressor suction and compressor discharge, the pressure equalisation valve comprising a bypass passage connecting the compressor suction to the compressor discharge to enable the compressor to be bypassed and a valve to control flow of refrigerant therethrough; and a liquid valve, preferably a liquid solenoid valve, arranged in a flow line between the heat rejecting heat exchanger and the expansion valve; characterised by further comprising: means for heating at least one component of the compressor; control means for activating the heating means when it is determined that compressor-startup is required, the control means starting the compressor after heating the at least one component; and at least one sensor, the sensor sensing at least one of the temperature of the oil in the compressor, the compressor shell temperature, the compressor discharge temperature, the ambient temperature and the length of time for which the compressor has been inactive; wherein the control means activates the heating means for a predetermined period of time based on at least one parameter of the system measured by the sensor, the predetermined period being based on at least one of the temperature of the oil in the compressor, the compressor shell temperature, the compressor discharge temperature, the ambient temperature and the length of time for which the compressor has been inactive. a compressor having a suction and a discharge; a heat rejecting heat exchanger; an expansion valve; a heat accepting heat exchanger; a pressure equalisation valve (40,42) for equalising the pressure differential between the compressor suction and compressor discharge, the pressure equalisation valve comprising a bypass passage connecting the compressor suction to the compressor discharge to enable the compressor to be bypassed and a valve to control flow of refrigerant therethrough; and a liquid valve, preferably a liquid solenoid valve, arranged in a flow line between the heat rejecting heat exchanger and the expansion valve; characterised by further comprising: means for heating at least one component of the compressor; control means for activating the heating means when it is determined that compressor-startup is required, the control means starting the compressor after heating the at least one component; and at least one sensor, the sensor sensing at least one of the temperature of the oil in the compressor, the compressor shell temperature, the compressor discharge temperature, the ambient temperature and the length of time for which the compressor has been inactive; wherein the control means activates the heating means for a predetermined period of time based on at least one parameter of the system measured by the sensor, the predetermined period being based on at least one of the temperature of the oil in the compressor, the compressor shell temperature, the compressor discharge temperature, the ambient temperature and the length of time for which the compressor has been inactive.