Installation For The First Time; Air Purging With Vacuum Pump; Air Purging By Refrigerant - Midea MSMBB-12CRDN1-MP0W Service Manual

6.4 Installation for the first time

Air and moisture in the refrigerant system have
undesirable effects as below:
● Pressure in the system rises.
● Operating current rises.
● Cooling or heating efficiency drops.
● Moisture in the refrigerant circuit may
freeze and block capillary tubing.
Water when mixed with the refrigerant and oil
●
will create an acid that will damage the motor
windings and components
system.
Therefore, the indoor units and the pipes
between indoor and outdoor units must be leak
tested and evacuated to remove gas and
moisture from the system.
Gas leak check (Soap water method):
Apply soap water or a liquid neutral
detergent on the indoor unit connections or
Connections with a soft brush
outdoor unit
check for leakage of the connecting points of
the piping. If bubbles come out, the pipes have
leakage.

1. Air purging with vacuum pump

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
Front seated
.
Connect the low pressure gauge to the 3 way
2)
service valve access port.
Connect the middle hose of the gauge
3)
in the refrigerant
to
.
manifold (usually yellow) to the vacuum
pump.
ully open the handle for the low pressure
4) F
gauge.
.
Start the vacuum pump and operate according
5)
to manufacture spec's
6) Perform an evacuation for a minimum of 30
minutes and check that the low pressure
(compound) gauge indicates a vacuum of 29.9
in/hg (500 microns) A vacuum gauge should
be used if available. If the proper vacuum
cannot be achieved the vacuum pump should
be run for an additional 20 minutes. If after the
additional 20 minutes the vacuum still cannot
be achieved the is a leak in the system and
must be located and repaired. follow the leak
checking procedure as mentioned before. If
the vacuum is achieved, close the low pressure
gauge handle off and shut the vacuum pump
off. Recheck the reading after 10 minutes, the
vacuum may change slightly, this is normal.
The system is now dry and free of
7)
contaminates, refrigerant pressure should
now be added to the system from a source
other than the system before opening the 2
way and 3 way valves for system operation.
The 2 way and 3 way valve can now be
8)
opened for the system operation

2. Air purging by refrigerant

Procedure:
1). Confirm that both the 2-way and 3-way
valves are set to the closed position.
With a container of refrigerant and a gauge
2).
manifold set, connect the low pressure gauge hose
13
.