Hitachi EXV-2.0E2 Manual De Instalación Y Funcionamiento página 18

REFRIGERANT PIPING AND CHARGE
7.3 BRAZING WORK
!
C A U T I O N
• Use nitrogen gas for blowing during pipe brazing. If oxygen, acetylene
or fluorocarbon gas is used, it will cause an explosion or poisonous
gas.
• A rust coating will appear inside of tubes if no nitrogen gas blowing
is performed during brazing work. This film will be flecked off
after operation and will circulate in the circuit, resulting in clogged
expansion valves, etc, and the compressor will be affected.
7.4 REFRIGERANT CHARGE
!
D A N G E R
• Do not charge OXYGEN, ACETYLENE, or other flammable and
poisonous gases into the refrigerant circuit, as an explosion could
occur. It is recommended that oxygen free nitrogen be charged for
these types of test cycles when performing a leakage test or an
airtight test. These types of gases are extremely dangerous.
• Insulate the unions and flare-nuts at the piping connection part
completely.
• Insulate the liquid piping completely to avoid a decreased performance;
if not, it will cause sweating on the surface of the pipe.
• Charge refrigerant correctly. Overcharging or insufficient charging
could cause a compressor failure.
• Check for refrigerant leakage in detail. If a large refrigerant leakage
occurred, it would cause difficulty with breathing or harmful gases
would occur if a fire were in the room.
• If the flare nut is tightened too hard, it may crack over time and cause
refrigerant leakage.
?
N O T E
Please refer to Outdoor unit Installation Manual and Technical Catalogue
for the calculating method of additional refrigerant charge according the
piping length.
7.4.1 DX-Interface refrigerant charge and
piping length limits
DX-Interface refrigerant charge calculation and limits of piping
length vs HEX volume is described in the following procedure,
that only applies to 1 to 1 system with UTOPIA IVX RAS-
XH(V)NP(1)E series and DX-Interface series 2. For any other
system the standard calculation procedure applies. Refer to the
Technical Catalogue of each system for further information.
The amount of refrigerant to be added to the system must be
calculated according to pipe length and the volume of the heat
exchanger (HEX), as well as the relation between these.
The following calculation procedure is applied only for 1-to-1
systems with UTOPIA IVX RAS-XH(V)NP(1)E series.
Total amount of refrigerant charge:
M
Total
Whereas charge due to increased pipe length is calculated as
follows:
m
And charge due to the volume of the heat exchanger (HEX) is
calculated as follows:
m
HEX
10 PMML0293A rev.2 - 08/2016
= m +m
L HEX
=(L-L )*α
L 0
=(V -V )*β
HEX 0
• Use a reducer valve when nitrogen gas blowing is performed during
brazing. The gas pressure should be maintained within 0.03 to 0.05
Mpa. If excessively high pressure is applied to a pipe, it will cause an
explosion.
There are different areas defined according to the length of
piping and the volume of the heat exchanger (HEX), as shown
in the following graphic. Depending on the area, it may be
necessary to calculate m , m
L
Heat exchanger (HEX) & pipe length
m
L
No additional
charge
0
0
The heat exchanger expansion volume is restricted to certain
applications. For those applications where it is not allowed,
standard volume and piping restrictions apply.
Each DX-Interface series 2 model has its own graphic, as shown
in the following page.
or both.
HEX
m m
HEX+ L
m
HEX
Heat Exchanger volume Vo (dm )
3