Midea MUBU-12HRFN1-M Service Manual page 45

1) Completely tighten the flare nuts of the
indoor and outdoor units, confirm that both
the 2-way and 3-way valves are set to the
closed position.
2) Connect the charge hose with the push pin
of handle lo to the 3-way valves gas service
port..
3) Connect the charge hose of handle hi
connection to the vacuum pump.
4) Fully open the handle Lo of the manifold
valve.
5) Operate the vacuum pump to evacuate.
6) Make evacuation for 30 minutes and check
whether the compound meter indicates
-0.1Mpa (14.5Psi). If the meter does not
indicate -0.1Mpa (14.5Psi) after pumping 30
minutes, it should be pumped 20 minutes
more. If the pressure can't achieve -0.1Mpa
(14.5Psi) after pumping 50 minutes, please
check if there are some leakage points.
Fully close the handle Lo valve of the
manifold valve and stop the operation of the
vacuum pump. Confirm that the gauge
needle does not move (approximately 5
minutes after turning off the vacuum pump).
7) Turn the flare nut of the 3-way valves about
45° counterclockwise for 6 or 7seconds
after the gas coming out, then tighten the
flare nut again. Make sure the pressure
display in the pressure indicator is a little
higher than the atmosphere pressure. Then
remove the charge hose from the 3 way
valve.
8) Fully open the 2 way valve and 3 way
valve and securely tighten the cap of the 3
way valve.
2. Air purging by refrigerant
Procedure:
1). Confirm that both the 2-way and 3-way
valves are set to the closed position.
2). Connect the charge set and a charging
cylinder to the service port of the 3-way valve.
3). Air purging.
Open the valves on the charging cylinder and
the charge set. Purge the air by loosening the
flare nut on the 2-way valve approximately 45'
for 3 seconds then closing it for 1 minute; repeat
3 times.
After purging the air, use a torque wrench to
tighten the flare nut on the 2-way valve.
4). Check the gas leakage.
Check the flare connections for gas leakage.
5). Discharge the refrigerant.
Close the valve on the charging cylinder and
discharge the refrigerant by loosening the flare
nut on the 2-way valve approximately 45' until
the gauge indicates 0.3Mpa (43.5Psi) to 0.5
Mpa (72.5Psi).
6). Disconnect the charge set and the charging
cylinder, and set the 2-way and 3-way valves to
the open position.
Be sure to use a hexagonal wrench to operate
the valve stems.
7). Mount the valve stems nuts and the service
port cap.
Be sure to use a torque wrench to tighten the
service port cap to a torque 18N· m.
Be sure to check the gas leakage.
12.4.4 Adding the refrigerant after running
the system for many years
Procedure
42