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TM5-4120-376-14
5-12. SYSTEM EVACUATION. Connects manifold gauge set to the suction and discharge
service valves and a hose to a vacuum pump. Start the pump and open both service valves and
open manifold gauge set valves. Operate the vacuum pump until pressure in the system is
reduced to 500 microns. Close manifold gauge set valve and turn the vacuum pump off. Let the
unit stand in this condition for at least one hour. If the system holds the vacuum, charge unit in
accordance with paragraph 5-13. If the 500 microns vacuum cannot be held for one hour, break
the vacuum repeat the leak checking procedure in accordance with paragraph 5-11. If 500
micron vacuum cannot be achieved, one or more of the following reasons may account for the
problem.
a. Presence Of Water Vapor In The System. Continued pumping will correct this condition.
b. Leaks In The Refrigeration System. Break the vacuum and retest for leaks in accordance
with paragraph 5-11.
c. Internal Leakage Of Vacuum Pump. Test the pump by connecting a vacuum gauge directly
to the vacuum pump intake and continue to pump. If pump still fails to reach 500 microns, the
pump is faulty.
5-14
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