Cassette Type Air Conditioner Unit
19
4.4.1 Vacuum
(1).
Remove the caps of the liquid valve, gas valve and also the service port.
(2).
Connect the hose at the low pressure side of the manifold valve assembly to the
service port of the unit’s gas valve, and meanwhile the gas and liquid valves
should be kept closed in case of refrigerant leak.
(3).
Connect the hose used for evacuation to the vacuum pump.
(4).
Open the switch at the lower pressure side of the manifold valve assembly and
start the vacuum pump. Meanwhile, the switch at the high pressure side of the
manifold valve assembly should be kept closed, otherwise evacuation would fail.
(5).
The evacuation duration depends on the unit’s capacity, generally, 20 minutes for
the 18k units, 30 minutes for the 24/36k units, 45 minutes for the 48/60k units. And
verify if the pressure gauge at the low pressure side of the manifold valve
assembly reads -1.0Mp (-75cmHg), if not, it indicates there is leak somewhere.
Then, close the switch fully and then stop the vacuum pump.
(6).
Wait for some time to see if the system pressure can remain unchanged, 5
minutes for the 18/24k units, 10 minutes for the units 36~60k. During this time, the
reading of the pressure gauge at the low pressure side can not be larger than
0.005Mp (0.38cmHg).
(7).
Slightly open the liquid valve and let some refrigerant go to the connection pipe to
balance the pressure inside and outside of the connection pipe, so that air will not
come into the connection pipe when removing the hose. Note that the gas and
liquid valve can be opened fully only after the manifold valve assembly is
removed.
(8).
Place back the caps of the liquid valve, gas valve and also the service port.
Hose with the valve pin
gauge manifold
Pressure gauge (Low-pressure)
Pressure gauge (Hi-pressure)
Switch (Low-pressure)
Switch (Hi-pressure)
Connection pipe (to indoor unit)
Liquid valve
Gas valve
Service port
Cap
Hose
Vacuum pump
Cap
Service pipe
Cap
Connection pipe
Fig. 4.18
