DC Inverter Multi
VRF Service Manual
119
Wrap the thermal insulation pipes with tapes, thus to extend their ageing time
5.10.2 Cautions:
The thermal insulation materials shall be able to withstand the pipe temperature. For heat pump unit, it is required
to withstand a temperature not lower than 70
on liquid pipe side and not lower than 120 on gas pipe side. For cooling-
only unit, it is required to withstand a temperature not lower than 70 on both liquid pipe side and gas pipe side.
Example: Heat resistant PVC foam (over 120 ); Foam PVC (over 100 )
The connector between indoor unit and outdoor unit shall be wrapped with thermal insulation materials, and shall
have no clearance to the wall on which the outdoor unit is mounted, as shown below.
NoGap
When wrapping the thermal insulation tape, each circle shall suppress half of the previous circle. To avoid reducing
the thermal isolation effect, do not wrap the tapes too tight.
After completing the protection work and wrapping the pipes, use the sealing materials to block the holes in the
wall.
5�11 Vacuum Pumping
5.11.1 Purposes of vacuum pumping
Discharge air and nitrogen in the piping to obtain vacuum state.
Vacuum is dry, capable to remove moisture in the system.
Under atmospheric pressure, the boiling point of water is 100
. But with increased vacuum degree created by
vacuum pump, the boiling point rapidly reduces. If boiling point reduces below ambient temperature, moisture in piping
will be evaporated. If vacuum is 0Kgf/cm2of absolute pressure (gauge pressure is -1Kgf/cm
2
), moisture in the system can
be evaporated totally
5.11.2 Selection of vacuum pump
Proper vacuum pumps must be selected before vacuum pumping. Insufficient capacity of selected vacuum pump
would lead to overtime of vacuum pumping and fall short of the requirement for vacuum degree. A proper vacuum pump
can obtain vacuum degree of 0Kgf/cm2 (gauge pressure -1 Kgf/cm2) after vacuum pumping.
Features of a vacuum pump shall be determined by two factors as follows:
Selection of a pump that can meet expected requirement (i.e. gauge pressure of -0.1MPa shall be obtained)
Exhaust ow is high (over 40L/min).
The following vacuum pumps are recommended
Model Maximum vacuum air displacement
Use
Air discharge Vacuum drying
Lubricant shaft pump 100L/min Suitable Suitable
Non-lubricant shaft pump 50L/min Suitable Suitable
Comparison table of different pressure units is as follows:
Unit Standard air pressure Vacuum degree
Relative pressure kg/cm2 0 -1.033
Absolute pressure kg/cm2 1.033 0
mmHg mmHg 0 -755
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