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Mounting The Branch Box; Installing Refrigerant Piping - Mitsubishi Electric PAC-MK52BCB Installation Manual

Air-conditioners indispensable optional parts branch box, hfc utilized, r410a, only for r410a outdoor unit, only for indoor use.
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6. Mounting the Branch Box

( )
Fig. 6-1
Fig. 6-2

7. Installing refrigerant piping

• Use refrigerant piping made of phosphorus deoxidized copper and cop-
per 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.
– R410A is a high-pressure refrigerant and can cause the existing piping to
• Store the piping to be used during installation indoors and keep both ends
of the piping sealed until just before brazing. (Store elbows and other joints
in a plastic bag.)
– If dust, dirt, or water enters the refrigerant cycle, deterioration of the oil
and compressor failure may result.
• After pipe connection, be sure to check that there is no gas leakage, using
a leak detector or soap-and-water solution.
• Before brazing the refrigerant piping, always wrap the piping on the main
body, and the thermal insulation piping, with wet towels to prevent heat
shrinkage and burning the thermal insulation tubing. Take care to ensure
that the fl ame does not come into contact with the main body itself. (Fig.7-1)
• Do not use leak-detection additives.
Cool them with wet
towels and so on.
Fig. 7-1
Place to be brazed
Note: Do not block the exit side.
When inner pressure
exceeds atmospheric
pressure, pin holes are
created which may cause
leaks from the brazed area.
Fig. 7-2
* Purchase an appropriate
bracket locally if the unit
is to be mounted on a
Pressure reducing valve (regulator)
Nitrogen gas pressure
0.02MPa or less
Hand valve
to prevent air
from entering.
Be sure to use the pressure reducing valve.
Be sure to use nitrogen gas. (Do not use
oxygen, carbon dioxide, or CFC gas.)
(1) Install the suspension bolts (procure locally) at the specifi ed pitch (Fig. 4-2, 4-3).
(2) Fit the washers (1, 2) and nuts (procure locally) to the suspension bolts.
(Fig. 6-1)
(3) Hang the unit on the suspension bolts.
(4) Fully tighten the nuts (check ceiling height).
(5) Use a level to adjust the branch box to the horizontal.
When unit is hung and nuts tightened
Suspension bolt
Nut (procure locally)
Washer (with cushion) 1
Ensure that cushion faces downwards
Washer (without cushion) 2
Nut (procure locally)
Ceiling board
► Connect the liquid and gas pipes of each indoor unit to the same end
connection numbers as indicated on the indoor unit flare connection
section of each Branch Box.
► When connecting indoor units, make sure to connect refrigerant pipes
and connection wires to the appropriate connection ports marked with
matching alphabets. (Ex. A, B, C, D, E) If connected to wrong end con-
nection numbers, it doesn't work normally.
Be sure to mark all the local refrigerant piping (liquid pipes, gas pipes, etc.)
for each indoor unit designating clearly which room it belongs in. (Ex. A, B,
C, D, E)
► List indoor unit model names in the name plate of Branch Box (for iden-
tification purposes).
• Conduct suffi cient anti-condensation and insulation work to prevent water drip-
ping from the refrigerant piping. (liquid pipe/gas pipe)
• Increase insulation depending on the environment where the refrigerant piping is
installed, or condensation may occur on the surface of the insulation material.
(Insulation material Heat-resistant temperature: 120 °C, Thickness:
15 mm or more)
* When the refrigerant piping is used in locations subject to high temperature
and humidity such as in the attic, further addition of insulation may be re-
• Insulate the liquid and gas pipes of the branch box by attaching the heat-resis-
tant polyethylene foam tightly around them. (Fig. 7-6)
Otherwise, a burn during pipe connection work or water leakage due to con-
densation on pipes may result.
► When using commercially available refrigerant piping, ensure that both
liquid and gas piping are wrapped with commercially available thermal
insulation materials (insulation materials at least 12 mm thick and able
to withstand temperatures in excess of 100 ºC).
► Refer to the installation manual of the outdoor unit when creating a
vacuum and opening or closing valves.
When connecting piping by brazing, be sure to use nitrogen-substituted non-
oxidation brazing. Do not use commercial antioxidants which may cause pipe
corrosion and degradation of refrigerator oil. Use non-oxidation brazing, or the
compressor may be damaged. (Fig. 7-2)
*1 Properly ventilate during brazing work. Before brazing in a closed room or a
small room, make sure that there is no refrigerant leakage. Buildup of leaked
refrigerant poses toxicity and combustion issues.
*2 Keep ignition sources, such as gas burning appliances and electrical heater,
etc., away from where the air conditioner is being installed or repaired.
*3 Use good quality brazing fi ller metal.
*4 When using fl ux, pay attention to the following points.
• After brazing, completely remove flux. If the chlorine contained in the
fl ux remaining in the pipe, the refrigerator oil is degraded and it becomes



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