PREVAC is essential component for low pressure chillers using refrigerants R-1233zd, R-123, R-11. PREVAC prevents air infiltration, that prevents surging start-ups, acid damage to refrigerant, extends chiller life as well as the purge. PREVAC provides push button pressurization for leak testing eliminating the unsafe temporary pressurization methods thus providing safe, efficient servicing. PREVAC is the best insurance policy you can buy for the chiller and personnel.