Make sure there is no any dirt or water before connecting
the piping to the outdoor units.
Wash the piping with high pressure nitrogen, never use
refrigerant of outdoor unit.
4.7 Remove Dirt or Water in the Piping
4.8 Airtight Test
Air tightness test – nitrogen must be used. (See the figure on
the right for the location of the maintenance access).
Increase the pressure from the liquid pipe and gas pipe to 4.0
MPa at the same time (not exceeding 4.0 MPa). If the pressure
does not drop in 24 hours, the test is passed.
When the pressure drops, check the leakage position (after
you make sure that there is no leakage, discharge the nitrogen).
CAUTION
Never use oxygen, combustible gas, or poisonous gas in the air
tightness test.
To prevent damage to the equipment, the pressure must not be
held for too long.
9
4.9 Air Purge with Vacuum Pump
4.10 Refrigerant Amount to be Added
Use a vacuum pump that can evacuate the pipe to the pressure
of less than -100.7 kPa (5 Torr, -755 mmHg). When the pump is
stopped, do not let the pump oil fow back into the refrigerant
pipe.
The liquid and gas pipes should be evacuated with a vacuum
pump for more than two hours to the pressure of less than
-100.7kPa. Then, place the pipes with the pressure of less than
-100.7 kPa for more than one hour, and check whether the
reading of the vacuum gauge rises. (If the reading rises, there is
residual water or gas leakage in the system. The leakage must
be checked and solved and the test should be performed again.)
Water may enter into pipes in the following conditions: the
installation is carried out in rainy seasons and the installation
period is long; the pipes are condensed inside; rainwater enters
the pipes.
After the above vacuum drying of two hours, use nitrogen to
increase the pressure to 0.05 MPa (vacuum breaking), and use
a vacuum pump to decrease the pressure to lower than -100.7kPa
or below and hold the pressure for one hour (vacuum drying).
Calculate the amount of the R410A refrigerant to be added based
on the diameter and length of the liquid pipes of the ODU and IDUs.
NOTE
Additional refrigerant volume of divergent pipe is 0.1kg
per item (Consider the liquid side of divergent pipe only)
CAUTION
Use a vacuum pump to perform the vacuuming process. Do not
use refrigerant gas to discharge air.
Use a vacuum pump that can vacuumize the pipe to the pressure
of less than -100.7 kPa (5 Torr, -755 mmHg). When the pump is
stopped, do not let the pump oil flow back into the refrigerant
pipe.
In order to prevent the entry of impurities, the R410A special tool
must be used to ensure the compression strength. Use a filling
hose with a top rod to connect to the maintenance access of
the check valve or the refrigerant filling port.
Liquid Side Piping
Diameter
Refrigerant to be Added
Permitted Piping
Φ9.5
Φ12.7
Φ15.9
0.054kg
0.110kg
0.170kg
Φ6.4
0.022kg
Table 4-12
When the outdoor unit connects 1 indoor unit:
The second Connect method
Indoor unit
a
N
1
3
N
N
5
N
6
N
2
N
4
Outdoor unit
A
B
D
E
C
b
c
e
f
d
1
L
2
L
5
L
3
L
4
L
Drop HEIGHT
between indoor unit and outdoor unit
Maximum pipe equivalent length
Pipe length(From the nearest branch
pipe equivalent length
(From the first line branch pipe)
Maximum pipe equivalent length
Indoor Unit to Indoor Unit Drop Heigh
t
The First Line Branch Pipe
Fig.4-8
(If the pressure cannot be decreased to lower than -100.7 kPa after
two-hour vacuuming, repeat the vacuum breaking and vacuum
process.) After that, place the vacuum pipes for one hour, and
then check whether the reading of the vacuum gauge rises.