A
CU MANUAL
IOM-14
24 of 46
Feb 06 R4
WARNING:
Test pressures must not exceed the maximum pressure ratings specified on the unit
rating plate.
WARNING:
Oxygen must NEVER be used to pressurize a system.
If leaks are located, remove pressure and repair leaks. Recheck as necessary. If brazing is necessary to
repair leaks, a dry nitrogen purge through tubing while brazing is required to prevent the formation of
copper oxides.
Evacuation and Dehydration
The system must be evacuated prior to charging. Proper evacuation will remove non-condensable gasses
and water vapor from the system. Water vapor in the system will combine with the oil and refrigerant to
form acids and other undesirable by-products. Non-condensable gasses such as air or nitrogen will
increase the head pressure and operating temperature and degrade system performance.
Sketch a piping schematic showing all valves and components. Check the diagram to ensure that all
portions of the system will be evacuated. Add additional hoses or service fittings as required.
NOTE:
A high vacuum cannot be pulled through a solenoid valve whether or not is energized.
A high vacuum cannot be pulled through a check valve regardless of direction of flow.
Evacuation Procedure:
1.
Remove leak-testing gasses from the system. If refrigerant was used to leak test, the refrigerant
shall be recovered.
2.
Connect a high vacuum pump to the system. Use the shortest and largest diameter hose available.
3.
Use as many connections as the system will allow.
4.
If evacuating through ‘Schraeder valves’, remove the Schraeder valve core before evacuation.
5.
Open all service valves.
6.
Use a micron gauge to measure the vacuum.
NOTE:
A standard refrigeration gauge with “inches of mercury” is not suitable to measure the high
vacuums. A high vacuum gauge capable of measuring Microns is required.
7.
Triple evacuation or high evacuation methods are both acceptable.
8.
Evacuate the system to an ultimate vacuum of 500 microns (0.5mm of mercury).
9.
Check unit rating-plate for correct refrigerant type. Break the vacuum with virgin refrigerant from a
sealed container.
