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 TM 55-1905-219-14-8
4-28. AIR CONDITIONING SYSTEM - MAINTENANCE INSTRUCTIONS (Continued).
f.
Refrigerant Charge.
(1)
The initial refrigerant charge for the entire system was done at a shipyard. This is an estimated
quantity based on the internal volume of system piping and components.
(2)
In practice, it may be necessary to add or remove refrigerant. High head pressure may indicate
refrigerant overcharge. Low head pressure may indicate refrigerant undercharge. (Refer to troubleshooting in
Volume 3 for other possible causes of high or low head pressure.)
(3)
The actual amount of refrigerant to be removed from or added to a charged system for optimum
operation must be determined by trial and error. Add or remove small amounts to obtain desired head pressure
(not to exceed 125 psig (861.9 kPa).
(4)
Charging Refrigerant.
(a) Liquid refrigerant is charged into the system through the charging valve connected to the main
liquid line upstream of the dryer. Pressure in the refrigerant drum forces the liquid refrigerant through the dryer,
liquid line and thermal expansion valves. The refrigerant evaporates in the cooling coils or other evaporator. It
is withdrawn by the compressor and pumped into the condenser where it is liquefied and drains to collect in the
receiver. To charge with refrigerant, proceed as outlined below:
1 Check compressor oil level, line up condenser sea water and refrigerant system valves, start
air circulating fans or circulating pump(s) if brine or chilled water is to be cooled, and start sea water flow
through condenser. Refer to paragraph 4-28e(2) steps (a) through (g).
NOTE
When adding refrigerant to a charged system, leave valves in their normal operating
positions and start with step (2) below.
2
Close dryer bypass and inlet valves, if dryer is provided with bypass. If not, close dryer inlet
valve. Refrigerant must be charged through dryer to exclude air and moisture from
system.
3
Check to see that solenoid valves are open. The solenoid thermostat contacts should be
closed and a humming sound should be heard with ear pressed against
solenoid valve casing.
4-840
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