Additional Refrigerant Charge; Engineering Of Insulation - Midea MTIU-07HWFNX-QRD0W Technical Manual

8. Additional Refrigerant Charge

•
After the vacuum drying process is carried out, the
additional refrigerant charge process need to be
performed.
•
The outdoor unit is factory charged with refrigerant.
The additional refrigerant charge volume is decided
by the diameter and length of the liquid pipe be-
tween indoor and outdoor unit. Refer the following
formula to calculate the charge volume.
Diameter of liquid pipe (mm)
6.35
9.52
The pre-charge pipe length is 7.5m.
Note:
•
Refrigerant may only be charged after performed
the vacuum drying process.
•
Always use gloves and glasses to protect your hands
and eyes during the charge work.
•
Use electronic scale or fluid infusion apparatus to
weight refrigerant to be recharged. Be sure to avoid
extra refrigerant charged, it may cause liquid ham-
mer of the compressor or protections.
•
Use supplementing flexible pipe to connect refriger-
ant cylinder, pressure gauge and outdoor unit. And
The refrigerant should be charged in liquid state.
Before recharging, The air in the flexible pipe and
manifold gauge should be exhausted.
•
After finished refrigerant recharge process, check
whether there is refrigerant leakage at the connec-
tion joint part.(Using gas leakage detector or soap
water to detect).
Formula
V=15g/m×((Total pipe
length - pre-charge
pipe lengthxN))
V=30g/m×((Total pipe
length - pre-charge
pipe lengthxN))

9. Engineering of Insulation

9.1 Insulation of refrigerant pipe
1. Operational procedure of refrigerant pipe
insulation
Cut the suitable pipe → insulation (except joint section) →
flare the pipe → piping layout and connection→ vacuum
drying → insulate the joint parts
2. Purpose of refrigerant pipe insulation
•
During operation, temperature of gas pipe and
liquid pipe shall be over-heating or over-cooling
extremely. Therefore, it is necessary to carry out in-
sulation; otherwise it shall debase the performance
of unit and burn compressor.
•
Gas pipe temperature is very low during cooling.
If insulation is not enough, it shall form dew and
cause leakage.
•
Temperature of gas pipe is very high (generally 50-
100°C) during heating. Insulation work must be
carried out to prevent hurt by carelessness touching.
3. Insulation material selection for refrigerant pipe
•
The burning performance should over 120°C
•
According to the local law to choose insulation
materials
•
The thickness of insulation layer shall be above
10mm.If in hot or wet environment place, the layer
of insulation should be thicker accordingly.
4. Installation highlights of insulation construction
•
Gas pipe and liquid pipe shall be insulated sepa-
rately, if the gas pipe and liquid pipe were insulated
together; it will decrease the performance of air
conditioner.
•
The insulation material at the joint pipe shall be
5~10cm longer than the gap of the insulation mate-
rial.
•
The insulation material at the joint pipe shall be
inserted into the gap of the insulation material.
•
The insulation material at the joint pipe shall be
banded to the gap pipe and liquid pipe tightly.
•
The linking part should be use glue to paste to-
gether
•
Be sure not bind the insulation material over-tight, it
may extrude out the air in the material to cause bad
 Page 133 