Vacuum Pumping - Gree DC Inverter Multi VRF Service Manual

DC INVERTER MULTI VRF
unit, it is required to withstand a temperature not lower than 70
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
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.
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.

6.11 Vacuum Pumping

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/cm
pressure (gauge pressure is -1Kgf/cm
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/cm
2
-1 Kgf/cm ) 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 flow is high (over 40L/min)
The following vacuum pumps are recommended.
Model
Lubricant shaft
pump
Non-lubricant shaft
pump
Comparison table of different pressure units is as follows:
Relative pressure
Absolute pressure
mm Hg
3 Vacuum pumping
The steps are as follows:
a. Expel the nitrogen after leakage detection;
Connect the pressure gauge to Freon nozzle on outdoor liquid valve and gas valve, and connect a
vacuum pump. Then, establish vacuum simultaneously from high pressure side and low pressure
side.
No clearance
2
), moisture in the system can be evaporated totally
Maximum vacuum air
displacement
100L/min
50L/min
Unit
2
kg/cm
2
kg/cm
mmHg
on liquid pipe side and not lower
100
Use
Air discharge Vacuum drying
Suitable Suitable
Suitable Suitable
Standard air
Vacuum degree
pressure
0
1.033
0
INSTALLATION
2
of absolute
2
(gauge pressure
-1.033
0
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