Gree GMV-Pdm450W/NaB-M

DC Inverter Multi
VRF Service Manual
117
5�9 Pressure Maintaining and Leak Hunting
5.9.1 Pressure maintaining of refrigerant piping
After refrigerant piping of a system is welded,
A refrigerant lling nozzle shall be welded respectively on the big pipe and on the small pipe on the outdoor unit
side.
Pipes connected to the end of indoor unit and outdoor unit shall be clamped to be at and welded to be sealed.
Enter into the step of connection pipe pressure keeping and leak hunting
Operating Steps:
Locate and repair leakage
Finish
Check
pressure drop
PressurizationComplete the
installation of piping
Pressurization
Use nitrogen to add pressure from Freon nozzle of the gas and liquid pipe on outdoor unit side:
Step 1: Increase the pressure to 0.3MPa and wait for 3 minutes or longer
Step 2: Increase the pressure to 1.5MPa and wait for 3 minutes or longer
The step 1 and 2 are focused on checking the significant leakage point. If any, reweld immediately or repair the
leakage point.
Step 3: Increase the pressure to 2.5MPa and keep it for approx. 24 hours to check the small leakage.
Though the pressure is increased to 2.5MPa, it cannot be guaranteed to nd out the small leakage if the waiting time
is too short. Therefore, the pressure in Step 3 must be kept for 24 hours.
Note: During pressure maintaining after nitrogen is filled, the pressure gauge shall not be dismantled, because
activities of dismantling or mounting pressure gauge would affect pressure change
Check pressure drop
Criteria for Inspection eligibility:
Except for temperature inuences (pressure changes about 0.01MPa for temperature change of 1 ), if pressure
drop is not more than 0.02MPa within 24h, the system will be eligible.
For example, nitrogen is lled to reach 2.5MPa at 30
; after 24 hours, when temperature becomes 25 , the system
will be eligible if pressure is over 2.43 MPa and ineligible below 2.43 MPa.
If ineligible, leak sources must be located. After leak sources are found, re-welding or repair welding is necessary.
Then, the above procedures shall be repeated. Nitrogen is lled, pressurized and maintained until pressure drop remains
within required range.
Leak check
[Check 1] When pressure drop is found, leak hunting shall be performed in the ways as follows:
a. By ears…….to listen voices related to leakage
b. By hands……to sense whether leakage is existent at connecting parts
[Check 2] If no leakage is found using the above methods, nitrogen shall be discharged and refrigerant shall be lled
in to reach 0.5MPa
a. By soap and water……soap bubbles will show leakage positions if any.
b. Detector (such as halide detector) can be used for leak hunting.
Using the above methods, check all possible leak sources.
If leakage still fails to be located, sectional check shall be taken for refrigerant piping that would be divided into
multiple check portions for locating leak source in a certain section.