Mitsubishi Electric ECOV-X37VA Manuel D'installation page 32

6. Apply a foaming agent. If no bubbles occur, there are no leaks.
Leave the system in the defined value for 24 hours. If the pressure is maintained, there are no leaks.
When the outside air temperature changes by 1°C, the pressure changes by approximately 0.01 MPa. Adjust the test con-
ditions as necessary.
If the pipe is pressurized before cooled down after welding, the pressure drops after the pipe cools down.
The pressure changes (up/down) depending on the outside air temperature. (Gas in the container (scale-invariant) is in
proportion to absolute temperature.)
Absolute pressure during measurement = absolute pressure during pressurization ×
(273°C + temperature during measurement) / (273°C + temperature during pressurization)
Absolute pressure = gauge pressure + 0.10133 (MPa)
(Gauge pressure indicates the gauge manifold-specified value.)
A pressure drop indicates a refrigerant leakage in the system. Find the refrigerant leaking area, and fix it.
If a leakage is found, inspect the welded part using soap water.
Nitrogen purge must be done before welding.
8-1-4. Refrigerant leakage detection
Special care for refrigerant leakage is important. Use a refrigerant leak detector for R744.
8-2. Vacuum drying
8-2-1. Purpose of vacuum drying
Completely evaporate any moisture that has entered the evaporator from the refrigerant pipes using vacuum in order to re-
lease it outside the system.
8-2-2. Vacuum drying procedure
[1] Level standard of a vacuum pump
Use a vacuum pump capable of attaining a vacuum pressure of 66 Pa at a point of 5 minutes from the startup of operation.
[2] Vacuum drying time
1)Perform vacuum drying for one hour after the vacuum level reaches 266 Pa on the vacuum gauge. (Thorough
vacuum drying eliminates moisture in the pipes.)
2)Check that the vacuum pressure does not drop one hour after the vacuum drying is completed.
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