Gree GMV-VQ280WM/C-X Owner's Manual page 41

GMV Heat Recovery DC Inverter VRF
4) The pressure should remain unchanged to be qualified.
5) If it is necessary to maintain pressure for a long time, the pressure should be reduced to
0.5 MPa or less. Long periods of high pressure can cause leakage at the weld site and
there is safety hazard.
6) Before the air tightness test for the refrigerant pipe is completed, it is not allowed to
conduct the insulation and wrapping work for any joints between the welding point and the
bell mouth of indoor unit. Please increase pressure from the outdoor side pipes at the
same time. It is forbidden to increase pressure from one side pipe:
NOTE: All welding points can't be heat-insulated and wrapped until the air tightness test is
completed.
(2) Operation procedures for the air tightness test
When leaving the factory, low pressure gas pipe, high pressure gas pipe, liquid pipe and stop
valve of outdoor unit have been closed. Please confirm it during installation.
Before the test, a small amount of lubricant oil required by the corresponding system should be
smeared at the nut and the end of the pipe. Two wrenches should be used when fixing the nut.
It is not allowed to connect the pipeline of outdoor unit for test during the air tightness test.
The test pressure for R410A system is 4.15 MPa. The air tightness test must use nitrogen as the
medium and the nitrogen should be dried. Slowly increase the pressure in three steps:
Step 1: Slowly increase the pressure to 0.5MPa, stay for 5 minutes and conduct the leakage
inspection. You may find big leakage.
Step 2: Slowly increase the pressure to 1.5MPa, stay for 5 minutes, conduct the air tightness
inspection, and you may find small leakage;
Step 3: Slowly increase the pressure for R410A system to 4.15 MPa, stay for 5 minutes and
conduct the strength test. You may find small penetration or blisters. After increasing the pressure to
the test pressure, hold the pressure for 24 hours, and observe whether the pressure drops. If the
pressure does not drop, it is qualified.
3.6.2 Vacuum Drying
(1) Selection requirements for vacuum pumps.
1) Can't vacuumize different refrigerant systems with the same vacuum pump.
2) The ultimate vacuum of the vacuum pump should be -0.1Mpa.
3) The air displacement of the vacuum pump should be above 4L/S.
4) The accuracy of the vacuum pump should be above 0.02mmHg.
5) The system vacuum pump must have a check valve.
Fig.3.6.1
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