HTW MI2 Serie Manuel D'installation page 38

4. Refrigerant Piping Installation
4.1 Length and Level Difference Requirements for the Piping
Connections to the Indoor and Outdoor Units
The length and level difference requirements for the refrigerant piping
are different for different indoor and outdoor units. Refer to the
installation manual of the outdoor unit.
4.2 Piping Material and Size
1. Piping material: Copper pipes for air handling.
2. Piping size: Choose and purchase copper pipes that correspond to
the length and size calculated for the selected model in the installation
manual of the outdoor unit and your actual project requirements.
4.3 Piping Layout
1. Seal the two ends of the piping properly before you connect the
indoor and outdoor piping. Once unsealed, connect the piping of
the indoor and outdoor units as quickly as possible to prevent dust
or other debris from entering the piping system via the unsealed
ends, as this may cause the system to malfunction.
2. If the piping needs to go through walls, drill the opening in the wall, and
place accessories like casings and covers for the opening properly.
3. Place the refrigerant connecting piping and the communication
wiring for the indoor and outdoor units together, and bundle them
tightly to make sure air does not enter and condensate to form
water that may leak from the system.
4. Insert the bundled piping and wiring from outside the room through
the wall opening into the room. Be careful when you lay out the
piping. Do not damage the piping.
4.4 Piping Installation
 Refer to the installation manual attached with the outdoor unit on
installation of the refrigerant piping for the outdoor unit.
 All gas and liquid piping must be properly insulated; otherwise, this
may cause water to leak. Use heat insulation materials that can
withstand high temperatures above 120°C to insulate the gas pipes.
In addition, the insulation of the refrigerant piping should be reinforced
(20 mm or thicker) in situations where there is high temperature
and/or high humidity (when part of refrigerant piping part is higher
than 30°C or when the humidity exceeds RH80%). Otherwise, the
surface of the heat insulation material may be exposed.
 Before the works are carried out, verify that the refrigerant is
R410A. If the wrong refrigerant is used, the unit may malfunction.
 Other than the specified refrigerant, do not let air or other gases
enter the refrigeration circuit.
 If the refrigerant leaks during installation, make sure you fully
ventilate the room.
 Use two wrenches when you install or dismantle the piping, a
common wrench and a torque wrench. See Figure 4.1.
Pipe fittings
 Slot the refrigerant piping into the brass nut (accessory), and
expand the pipe socket. Refer to the following table for the size of
the pipe socket and the appropriate tightening torque.
External
Tightening torque
diameter (mm)
Φ6.35 14.2-17.2N·m
Φ9.53 32.7-39.9N·m
Φ12.7 49.5-60.3N·m
Φ15.9 61.8-75.4N·m
Φ19.1 97.2-118.6N·m
Caution
• Apply the appropriate tightening torque according to the
installation conditions. Excessive torque will damage the socket
cap, and the cap will not be tight if you apply insufficient torque,
leading to leakages.
Normal wrench
Torque wrench
Pipe socket cap
Figure 4.1
Flared opening
Flared opening
diameter (A)
8.3-8.7mm
90°±4
12-12.4mm
A
15.4-15.8mm
18.6-19mm
Figure 4.2
22.9-23.3mm
 Before the socket cap is installed on the pipe socket, apply some
refrigerant oil on the socket (both inside and outside), and then rotate
it three or four times before you tighten the cap. See Figure 4.3.
Precautions to take when welding the refrigerant pipes
• Before you weld the refrigerant pipes, fill the pipes with nitrogen
first to discharge the air in the pipes. If no nitrogen is filled during
welding, a large amount of oxide film will form inside the piping
which may cause the air conditioning system to malfunction.
• Welding can be carried out on the refrigerant pipes when the
nitrogen gas has been replaced or refilled.
• When the pipe is filled with nitrogen during welding, the nitrogen
must be reduced to 0.02 MPa using the pressure release valve.
See Figure 4.4.
Figure 4.4
4.5 Air Tightness Test
Carry out the air tightness test on the system according to the
instructions in the installation manual of the outdoor unit.
Caution
• The Air Tightness Test helps to ensure that the air and liquid
cut-off valves of the outdoor unit are all closed (maintain the
factory defaults).
4.6 Heat Insulation Treatment for Gas-Liquid Piping Connections
for the Indoor Unit
 The heat insulation treatment is carried out on the piping at the
gas and liquid sides of the indoor unit respectively.
a. The piping on the gas side must use heat insulation material
that can withstand temperatures of 120°C and more.
b. For the piping connections of the indoor unit, use the insulation
casing for copper pipes (accessory) to carry out the insulation
treatment, and close all gaps.
4.7 Vacuum
Create a vacuum in the system according to the instructions in the
45°±2
installation manual of the outdoor unit.
R0.4 ~ 0.8
Caution
• For the vacuum, make sure that the air and liquid cut-off valves
of the outdoor unit are all closed (maintain the factory status).
4.8 Refrigerant
Charge the system with refrigerant according to the instructions in the
installation manual of the outdoor unit.
9
Apply refrigerant oil
Figure 4.3
1 Copper piping
2 Section being brazed
3 Nitrogen connection
4 Hand valve
5 Pressure-reducing valve
6 Nitrogen
Face upwards
Unit
On-site piping side
Attached insulation
body
heat pump belt
Figure 4.5