Gree GMV-224WM/B-X, Service Manual

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GMV5 DC INVERTER VRF UNITS SERVICE MANUAL
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d) The communication cable must be long enough to avoid joints.
e) Indoor units must be connected in series. The last IDU shall be connected to a matching
resistor (placed in the package of the ODU).
Part 8: Vacuumization and Desiccation for
the Refrigerant System
Works for the refrigerant system include cleaning and desiccating the pipes, performing an air-tightness
test, and perfusing refrigerant.
I. Air-tightness Test
1. Importance of the Air-tightness Test
Air-tightness of the multi-module air conditioning system mainly refers to the tightness of the refrigerant
pipes, which ensures secure and reliable running of the air conditioner.
Refrigerant leakage may affect functions of the air conditions or even damage the compressor and make
the system to break down. Therefore, a air-tightness test must be performed. If refrigerant leakage is
detected after the system is installed, it is very difficult to locate the leaking point as the suspending
ceiling has been decorated. Therefore, the air-tightness test must be performed before ceiling sealing for
indoor decoration is finished.
2. Procedure for Performing the Air-tightness Test
Stop valves of the gas and liquid pipes of the ODU are turned off at delivery.
Before test, apply a small amount of required lubricant on the block nut and pipe terminals and use two
wrenches to fix the block nut.
The ODU pipes cannot be connected when the air-tightness test is being performed.
The test pressure for R410A system is 4.0 MPa. Use dry nitrogen as media for the air-tightness test.
Increase the pressure slowly by following the steps below:
Step 1: Increase the pressure to 0.5 MPa. Stop for 5 minutes and then perform air-tightness check. Major
leakage may be detected.
Step 2: Increase the pressure to 1.5 MPa. Stop for 5 minutes and then perform air-tightness check. Minor
leakage may be detected.
Step 3: Increase the pressure for R410A system to 4.15 MPa. Stop for 5 minutes and then perform
strength check. Slight leakage or blow holes may be detected.After increasing the pressure to the test
pressure, keep the pressure for 24 hours and check whether it decreases. If the pressure does not
decrease, it meets the requirement.
3. Precautions:
a. The measuring range of the test pressure gauge for R410A system must be above 4.5 MPa.
b. Record the value displayed on the pressure gauge, ambient temperature, and test time.
c. Pressure correction: The pressure changes by 0.01 MPa when the temperature changes by 1
°C.
d. The pressure meets the requirement if it does not change.
e. If the pressure must be kept for a long time, decrease the pressure to 0.5 MPa or lower. High pressure
for a long time may cause leakage at the welding point or safety hazard.
f. Before performing the air-tightness test to the refrigerant pipes, do not conduct insulation or wrapping
at the welding or flaring opening joints of the IDU. The pressure must be increased simultaneously for
pipes on outdoor sides and cannot be increased for pipes on one side.
4. Note: Before performing the air-tightness test, do not conduct insulation or wrapping at the welding
joints.