Non-condensable purge technique using refrigerant temperature offset

This application relates to refrigerant handling systems and, in particular, to systems for recovering and recycling refrigerant from cooling systems, such as those of automotive vehicles. The application relates in particular to techniques and apparatus for purging non-condensables from the recovered refrigerant. In a refrigerant recycling system non-condensables are purged from a recovery vessel which stores refrigerant recovered from a vehicular refrigeration system. A programmed controller controls operation of a purge valve for purging to atmosphere non-condensables in the recovered refrigerant in accordance with a purge routine, wherein the temperature in the recovery vessel is measured, and a look-up table is consulted to ascertain a target pressure corresponding to the measured temperature plus an offset, and the pressure in the recovery vessel is measured. If the measured pressure exceeds the target pressure, the purge valve is opened until the measured pressure drops to the target pressure. Immediately after a recovery operation, the purge routine is operated to purge the vessel to a target pressure based on an offset of 1° F. and, at a later time, after the vessel has cooled, the purge routine is operated to purge the vessel to a target pressure based on an offset of zero.