Flushing piping (a)
For outdoor unit, the liquid pipe, low pressure and high
# # $* *#*&
alternatively, one pipe can be flushed first and then
Steps 1 to 5 repeated, for another pipe. The flushing
procedure is as follows:
1. Attach a pressure reducing valve to a nitrogen
cylinder.
2. Connect the pressure reducing valve outlet to the
corresponding stop valve of the outdoor unit.
3. Start to open the nitrogen cylinder valve and gradually
increase the pressure to 0.5 MPa.
4. Allow time for nitrogen to flow as far as the outlet of
piping (a).
5. Flush piping (a):
a) Using suitable material, such as a bag or cloth, press
firmly against the outlet of piping (a).
b) When the pressure becomes too high to block with
your hand, suddenly remove your hand allowing gas to
rush out.
c) Repeatedly flush in this manner until no further dirt or
moisture is emitted from the piping. Use a clean cloth to
check for dirt or moisture being emitted. Seal the outlet
once it has been flushed.
6. Once flushing is completed, seal all main pipes to
prevent dust and moisture from entering.
Flushing piping (b)
The procedure for flushing piping (b) is similar to that for
piping (a). Flush nitrogen from one end of piping (b) . And
repeat steps until all indoor pipes are flushed.
1
2
3
4
5
Liquid pipe
Low pressure gas pipe
High pressure gas pipe
Indoor liquid pipe
Indoor gas pipe
Fig. 5-16
The refrigerant piping must to be flushed before
connecting to MS boxes to prevent impurities
from blocking the MS boxes.
CAUTION
Nitrogen gas braze protection on MS box
*#& # \# *
brazing. It is very important to charge nitrogen properly
during brazing.
a) Normal charge from port
ʓ
while brazing port
ʕ
and
strong charge (> 20 kPa) from port
ʓ
while brazing port
ʖ
as Fig.5-15.
#*# %#$
ʓ
while brazing
port
ʒ
and normal charge from corresponding outdoor
unit stop valve while brazing port
ʓ
and port
ʔ
as
Fig.5-15.
*Solenoid valve can be opened while downstream gas
pressure is 20 kPa above that of upstream.
5.5 Pipe Flushing
5.6 Gas Tightness Test
The refrigerant piping should be flushed using nitrogen
to remove dust, other particles and moisture, which
could cause compressor malfunction if not flushed out
before the system runs.
1. First, the refrigerant piping should be flushed with
nitrogen before brazing.
2. And Pipe flushing should be performed before
connecting refrigerant piping to MS boxes and indoor
units to prevent impurities from blocking the MS boxes
and indoor units.
a) Flush the refrigerant piping with nitrogen before
brazing.
b) Braze the refrigerant piping and branch joints between
outdoor unit(s) and MS box (piping (a) in Fig. 5-16), but
not connect piping (a) to MS box.
c) Flush piping (a) with nitrogen, and then connect piping
(a) to MS box according to the description of 5.4.8.
d) Braze the refrigerant piping and branch joints between
MS and indoor units (piping (b) in Figure 5.16), but not
connect piping (b) to MS box.
e) Flush piping (b) with nitrogen, and then connect piping
(b) to MS box according to the description of 5.4.8.
f) Flush all refrigerant piping from outdoor unit stop
valves to ensure no impurities remain.
g) Finally, connect piping (b) to indoor units.
Only use nitrogen for flushing. Using carbon
dioxide risks leaving condensation in the piping.
Oxygen, air, refrigerant, flammable gases and
toxic gases must not be used for flushing. Use of
such gases may result in fire or explosion.
CAUTION
Only dry nitrogen should be used for gas
tightness testing. Oxygen, air, flammable
gases and toxic gases must not be used for
gas tightness testing. Use of such gases may
result in fire or explosion.
Make sure that all the outdoor unit stop
valves are firmly closed.
CAUTION
MS
Piping (a)
Piping (b)
Piping (b)
Outdoor
unit
Indoor
unit A
Indoor
unit B
Nitrogen gas
cylinder
To prevent faults caused by refrigerant leakage, a gas
tightness test should be performed before system
commissioning.
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