Midea LC3 Series Technical & Service Manual page 82

Midea LC3 Series DC Inverter Air conditioner Technical Service Manual
MCAC-UTSM-202006
5. Connection of Connecting Pipe
5.1 Length and level difference requirements for the pipe connections of IDU and
ODU
Product Model
26/35
53/71
90/105
140/160
Notes: If the height difference is greater than the allowed level difference, it is recommended to place ODU
above the IDU.
Caution:
• Do not let air, dust, or other particles invade the pipeline system during installation of the connecting pipes.
• Install the connecting pipes only when the indoor and outdoor units are secured.
• Make sure to keep the connecting pipes dry during installation so that no water will enter the piping system.
• Connecting copper pipes must be wrapped with insulation materials (thicker than 10mm, the thickness
should be increased if the unit is installed in a closed humid place).
5.2 Steps of pipe connection
Measure the required length of the connecting pipe. Make the connecting pipe using the following method (see
the column Pipe Connection for details).
1. Connect the IDUs before the ODU.
• Bend and arrange pipes carefully without damaging the pipes and their insulating layers.
• Before tightening the flare nut, apply refrigerant oil on the outer surface at the pipe flaring position and the
conical surface of the connecting nut (the refrigerant oil used must be compatible with the refrigerant of this
model), and screw it 3 to 4 turns with your hand to tighten it as shown in the figure below.
• When connecting or removing a pipe, use two wrenches at the same time.
• Do not put the weight of the connecting pipe on the connector of the IDU. Otherwise, the heavy weight will
deform the connector and affect the cooling (heating) effect.
2. The check valve of the ODU should be completely closed (e.g. the ex-factory condition). Unscrew nuts from
the check valve in each connection, and connect the flared tube immediately (within 5 minutes). When the nut
at the check valve is removed and placed for too long, dust and other sundries may enter the pipeline system
and cause failures at a later time.
3. After the refrigerant pipe is connected to the IDU and ODU, discharge the air according to the column Air
Discharge. After the air is discharged, tighten the service nut.
Precautions for flexible pipes:
• Do not bend a pipe more than 90 degrees (see the figure below).
• The bend should be as close as possible to the center of the tube and the bend radius should not be less
Maximum length(m) Maximum level difference(m)
15
25
30
50
Bend the pipe with your thumbs
10
15
20
25
81
Maximum number of bends(m)
5
15
15
15