Information concerning the charging of refrigeration systems may be found in Naval Ships Technical Manual chapter 516. The amount of refrigerant charge must be sufficient to maintain a liquid seal between the condensing and the evaporating sides of the system. When the compressor stops, under normal operating conditions, the receiver of a properly charged system is about 85% full of refrigerant. The proper charge for a specific system or unit can be found in the manufacturers technical manual or on the ships blueprints.

A refrigeration system should not be charged if there are leaks or if there is reason to believe that there is a leak in the system. The leaks must be found and corrected. A system should be checked for leaks immediately followingor duringthe process of charging.

A refrigeration system must have an adequate charge of refrigerant at all times; otherwise its efficiency and capacity will be impaired.

PURGING THE SYSTEM

To determine if there are noncondensable gases in the system, close the liquid line stop valve. By-pass all evaporator pressure regulator valves and allow the system to pump down one or more times. Stop the compressor. By-pass the water regulating valve and circulate cooling water through the condenser. When discharge pressure stops dropping, convert the pressure to temperature and from this subtract the temperature of the injection or overboard. (They both should be equalized.) A variation of over 5 F will indicate that air and noncondensable gases are present in the system. Crack open the purge valve for 2-3 seconds at 2 to 3 minute intervals until the temperature is within 5 F.