SYSVRF2 IM

21
5.9 Charging refrigerant
Liquid side
piping (mm)
Additional refrigerant charge per meter
of equivalent length of piping (kg)
Φ6.4
Φ9.5
Φ12.7
Φ15.9
Φ19.1
Φ22.2
Φ25.4
Φ28.6
0.022kg
0.057kg
0.110kg
0.170kg
0.260kg
0.360kg
0.520kg
0.680kg
Table. 5-9
Fig.5-16
During vacuum drying, a vacuum pump is used to lower the pressure
in the piping to the extent that any moisture present evaporates. At
5mmHg (755mmHg below typical atmospheric pressure) the boiling
point of water is 0°C. Therefore a vacuum pump capable of
maintaining a pressure of -756mmHg or lower should be used. Using
a vacuum pump with a discharge in excess of 4L/s and a precision
level of 0.02mmHg is recommended.The vacuum drying procedure is
as follows:
Connect the blue (low pressure side) hose of a pressure gauge to
the master unit gas pipe stop valve, the red (high pressure side)
hose to the master unit liquid pipe stop valve and the yellow hose
to the vacuum pump.
Start the vacuum pump and then open the pressure gauge valves
to start vacuum the system.
After 30 minutes, close the pressure gauge valves.
After a further 5 to 10 minutes check the pressure gauge. If the
gauge has returned to zero, check for leakages in the refrigerant
piping.
1.
2.
3.
4.
Re-open the pressure gauge valves and continue vacuum drying
for at least 2 hours and until a pressure difference of 0.1Mpa or
more has been achieved. Once the pressure difference of at least
0.1Mpa has been achieved, continue vacuum drying for 2
hours.
Close the pressure gauge valves and then stop the vacuum pump.
After 1 hour, check the pressure gauge. If the pressure in the
piping has not increased, the procedure is finished. If the pressure
has increased, check for leakages.
After vacuum drying, keep the blue and red hoses connected
to
the pressure gauge and to the master unit stop valves, in
preparation for refrigerant charging.
5.
6.
7.
8.
CAUTION
Before performing vacuum drying, make sure that all the outdoor
unit stop valves are firmly closed.
Once the vacuum drying is complete and the vacuum pump is
stopped, the low pressure in the piping could suck vacuum pump
lubricant into the air conditioning system. The same could happen
if the vacuum pump stops unexpectedly during the vacuum drying
procedure. Mixing of pump lubricant with compressor oil could
cause compressor malfunction and a one-way valve should
therefore be used to prevent vacuum pump lubricant seeping into
the piping system.
CAUTION
Only charge refrigerant after performing a gastightness test and
vacuum drying.
Never charge more refrigerant than required as doing so can lead
to liquid hammering.
Only use refrigerant R410A - charging with an unsuitable
substance may cause explosions or accidents.
Use tools and equipment designed for use with R410A to ensure
required pressure resistance and to prevent foreign materials from
entering the system.
Refrigerant must be treated in accordance with applicable
legislation.
Always use protective gloves and protect your eyes when charging
refrigerant.
Open refrigerant containers slowly.
③
③
①
①
②
②
Vacuum pump
Pressure gauge
Yellow hose
Blue hose
Red hose
Master unit Slave unit
Slave unit
Field piping
Gas pipe stop valve
Liquid pipe stop valve
Service port
Additional refrigerant charge R (kg) = (T1@Φ6.35) × 0.022 +
(T2@Φ9.53) × 0.057 + (T3@Φ12.7) × 0.110 + (T4@Φ15.9) ×
0.170 + (T5@Φ19.1) × 0.260 + (T6@Φ22.2) × 0.360 + (T7@Φ
25.4) × 0.520 + (T8@Φ28.6) × 0.680
Calculating additional refrigerant charge
The additional refrigerant charge required depends on the lengths
and diameters of the outdoor and indoor liquid pipes. Table 5-9
shows the additional refrigerant charge required per meter of
equivalent pipe length for different diameters of pipe. The total
additional refrigerant charge is obtained by summing the additional
charge requirements for each of the outdoor and indoor liquid
pipes, as in the following formula, where T1 to T8 represent the
equivalent lengths of the pipes of different diameters. Assume 0.5m
for the equivalent pipe length of each branch joint.
The procedure for adding refrigerant is as follows:
1. Calculate additional refrigerant charge R (kg) .
2. Place a tank of R410A refrigerant on a weighing scale. Turn the
tank upside down to ensure refrigerant is charged in a liquid state.
(R410A is a blend of two different chemicals compounds.
Charging gaseous R410A into the system could mean that the
refrigerant charged is not of the correct composition).
3. After vacuum drying, the blue and red pressure gauge hoses
should still be connected to the pressure gauge and to the master
unit stop valves.
4. Connect the yellow hose from the pressure gauge to the R410A
refrigerant tank.