LG MULTI V Installation Manual page 50

Pipe connections between indoor and outdoor unit
Leak Test and Vacuum drying
(1) Leak test
Leak test should be made by pressurizing nitrogen gas to 3.8Mpa(551.1psi). If the pressure does not drop for 24
hours, the system passes the test. If the pressure drops, check where the nitrogen leaks. For the test method, refer
to the following figure. (Make a test with the service valves closed. Be also sure to pressurize liquid pipe, gas pipe
and high/low pressure common pipe)
The test result can be judged good if the pressure has not be reduced after leaving for about one day after completion
of nitrogen gas pressurization.
Nitrogen gas
cylinder
Nitrogen gas
cylinder
Note:
If the ambient temperature differs between the time when pressure is applied and when the pressure drop is
checked, apply the following correction factor
There is a pressure change of approximately 0.01Mpa(1.5psi) for each 1°C of temperature difference.
Correction= (Temp. at the time of pressurization – Temp. at the time of check) X 0.1
For example: Temperature at the time of pressurization 3.8MPa(551psi) is 27 °C
Caution:
To prevent the nitrogen from entering the refrigeration system in the liquid state, the top of the cylinder must be
at higher position than the bottom when you pressurize the system.
Usually the cylinder is used in a vertical standing position.
50 Outdoor Unit
Slave 1 outdoor unit
Close
Close
Close
24 hour later: 3.73MPa(541psi), 20°C
In this case the pressure drop of 0.07MPa(10psi) is because of temperature drop
And hence there is no leakage in pipe occurred.
Master outdoor unit
Close
Close
Close
Liquid side
Indoor unit
Gas side