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6. Refrigerant piping work
6.2. Refrigerant piping work
This piping work must be done in accordance with the installation manuals for
outdoor unit.
• For constraints on pipe length and allowable difference of elevation, refer to the
outdoor unit manual.
• The method of pipe connection is brazing connection.
Caution:
• Install the refrigerant piping for the indoor unit in accordance with the
following.
1. Cut the tip of the indoor unit piping, remove the gas, and then remove the brazed
cap.
[Fig. 6-2-1]
A Cut here
B Remove brazed cap
2. Pull out the thermal insulation on the site refrigerant piping, braze the unit piping,
and replace the insulation in its original position.
Wrap the piping with insulating tape.
Note:
• When blazing the refrigerant pipes, be sure to blaze, after covering a wet
cloth to the pipes of the units in order to prevent it from burning and
shrinking by heat.
[Fig. 6-2-2]
A
A Cool by a wet cloth
• Pay strict attention when wrapping the copper piping since wrapping the
piping may cause condensation instead of preventing it.
[Fig. 6-2-3]
A
C
B
A
D
E
F
A Thermal insulation
B Pull out insulation
C Wrap with damp cloth
D Return to original position
E Ensure that there is no gap here
F Wrap with insulating tape
Cautions On Refrigerant Piping
Be sure to use non-oxidative brazing for brazing to ensure that no foreign
matter or moisture enter into the pipe.
Be sure to apply refrigerating machine oil over the flare connection seating
surface and tighten the connection using a double spanner.
Provide a metal brace to support the refrigerant pipe so that no load is
imparted to the indoor unit end pipe. This metal brace should be provided
50 cm away from the indoor unit's flare connection.
Warning:
Do not use refrigerant other than the type indicated in the manuals provided
with the unit and on the nameplate.
- Doing so may cause the unit or pipes to burst, or result in explosion or fire during
use, during repair, or at the time of disposal of the unit.
- It may also be in violation of applicable laws.
- MITSUBISHI ELECTRIC CORPORATION cannot be held responsible for malfunc-
tions or accidents resulting from the use of the wrong type of refrigerant.
6
Caution:
• Use refrigerant piping made of C1220 (Cu-DHP) phosphorus deoxidized
copper as specified in the JIS H3300 "Copper and copper alloy seamless
pipes and tubes". In addition, be sure that the inner and outer surfaces of the
pipes are clean and free of hazardous sulphur, oxides, dust/dirt, shaving
particles, oils, moisture, or any other contaminant.
• Never use existing refrigerant piping.
- The large amount of chlorine in conventional refrigerant and refrigerator oil in the
existing piping will cause the new refrigerant to deteriorate.
• Store the piping to be used during installation indoors and keep both ends of
the piping sealed until just before brazing.
- If dust, dirt, or water gets into the refrigerant cycle, the oil will deteriorate and the
compressor may fail.
6.3. Purging procedures leak test
PURGING PROCEDURES
Connect the refrigerant pipes (both the liquid and gas pipes) between the indoor
and the outdoor units.
Remove the service port cap of the stop valve on the side of the outdoor unit gas pipe.
(The stop valve will not work in its initial state fresh out of the factory (totally closed
with cap on).)
Connect the gage manifold valve and the vacuum pump to the service port of the
stop valve on the gas pipe side of the outdoor unit.
Run the vacuum pump. (Vacuumize for more than 15 minutes.)
Check the vacuum with the gauge manifold valve, then close the gauge manifold
valve, and stop the vacuum pump.
Leave it as is for one or two minutes. Make sure the pointer of the gauge manifold
valve remains in the same position. Confirm that the pressure gauge show
-0.101MPa (-760 mmHg).
Stop valve
*Close
Stop valve
*Open
Hexagonal wrench
Service port
*4 to 5 turns
Remove the gauge manifold valve quickly from the service port of the stop valve.
After refrigerant pipes are connected and evacuated, fully open all stop valves on
gas and liquid pipe sides.
Operating without fully opening lowers the performance and causes trouble.
Pipe length :
7 m maximum
No gas charge is needed.
Tighten the cap to the service port to obtain the initial status.
Retighten the cap
Compound pressure
-0.101MPa
gauge (for R32/R410A)
(-760 mmHg)
Pressure gauge
(for R32/R410A)
Gauge manifold valve
(for R32/R410A)
Handle
Handle High
Low
Charge hose
Stop
(for R32/R410A)
valve
Vacuum
(or the vacuum
pump
Window
pump with the
function to
Adapter for
Charge hose
prevent the back
preventing
(for R32/R410A)
flow)
the back flow
Pipe length exceeding 7 m
Charge the prescribed
amount of gas.
Leak test
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