GMV DC Inverter VRF 
35 
Step 5 
 
 
①
 Pull the canvas casing 
upside down and press 
it on the butt flange of 
the steel pipe 
ventilation pipe with 
steel bars; 
②
 Drill holes with the 
manual drill and fix 
them with   
self-tapping screws; 
③
 Seal the two butt joints 
with tinfoil panel and 
check the reliability of 
the connection. 
___ 
3.6 Vacuum and Drying of Refrigeration System 
3.6.1 Air Tightness Test 
(1)  Notices   
1)  The range of test pressure gauge for R410A system should be above 4.5MPa. 
2)  Record the pressure gauge readings, ambient temperature and test time. 
3)  Pressure correction: The temperature changes by 1 
℃
, and the pressure changes by 
0.01MPa. 
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 
0.5MPa 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: