Add Refrigerant After Long-Term System Operation; Servicing Indoor Unit Refrigeration Circuit; Collecting Refrigerant Into Outdoor Unit; Air Purging With Vacuum Pump - Lennox MCB Series Service Manual

5.3. Add Refrigerant after Long-Term
System Operation
• Connect the charge hose to the three-way
service port and open the two-way and three-
way valve.
• Connect the charge hose to the valve at
the bottom of the cylinder. If the refrigerant
is R-410A, place the cylinder bottom-up to
ensure liquid charge.
• Purge the air from the charge hose.
• Open the valve at the bottom of the cylinder
and press the check valve on the charge
set to purge the air (be careful of the liquid
refrigerant).
• Place the charging cylinder onto the electronic
scale and record the weight.
• Turn on the air conditioner in cooling mode.
• Open the valves (Low side)on the charge set
and charge the system with liquid refrigerant.
• When the electronic scale displays the proper
weight (refer to the gauge and the pressure
of the low side), disconnect the charge hose
from the three-way valve's service port
immediately and turn off the air conditioner
before disconnecting the hose.
• Mount the valve stem caps and the service
port. Use torque wrench to tighten the service
port cap to a torque of 18N.m(13.27 ft·lbs).
• Be sure to check for gas leaks.
5.4. Servicing Indoor Unit Refrigeration
Circuit
5.4.1.

Collecting Refrigerant into Outdoor Unit

• Confirm that both the two-way and three-way
valves are set to the opened position
• Remove the valve stem caps and confirm that
the valve stems are in the opened position.
• Be sure to use a hexagonal wrench to operate
the valve stems.
• Connect the charge hose with the push pin of
handle lo to the three-way valves gas service
port.
• Air purging of the charge hose - Open the
handle Lo valve of the manifold valve slightly
to purge air from the charge hose for five
seconds and then close it quickly.
• Set the two-way valve to the close position.
• Operate the air conditioner at the cooling
cycle and stop it when the gauge indicates
0.1MPa (14 psi).
• Set the three-way valve to the closed
position immediately
• Do this quickly so that the gauge ends up
indicating 0.3 to 0.5Mpa (43 - 72 psi).
• Disconnect the charge set, and tighten the
two-way and three-way valve's stem nuts.
• Use a torque wrench to tighten the three-way
valves service port cap to a torque of 18N.m.
• Be sure to check for gas leakage.
5.4.2.

Air Purging with Vacuum Pump

• Completely tighten the flare nuts of the indoor
and outdoor units, confirm that both the
two-way and three-way valves are set to the
closed position.
• Connect the charge hose with the push pin of
handle lo to the three-way valves gas service
port.
• Connect the charge hose of handle hi
connection to the vacuum pump.
• Fully open the handle Lo of the manifold
valve.
• Operate the vacuum pump to evacuate.
• Make evacuation for 30 minutes and check
whether the compound meter indicates -
0.1Mpa (500 microns). If the meter does
not indicate - 0.1Mpa (500 microbars) after
pumping 30 minutes, it should be pumped 20
minutes more. If the pressure can't achieve
-0.1Mpa (500 microbars) 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 five minutes after
turning off the vacuum pump).
• Turn the flare nut of the three-way valves
about 45° counterclockwise for six or seven
seconds 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 three-way
valve.
• Fully open the two-way valve and three-way
valve and securely tighten the cap of the
three-way
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