Hitachi FSXN Series Service Manual page 47

3 Piping work and
refrigerant charge
¿ Flared connection mounting
Apply a thin layer of oil to the cone opening for refrigeration
systems.
Line up the end of the flared pipe to face the fitting to which it is to
be threaded.
Gently rest the female cone on the male cone and check that the
measurement is correct. Keep the connection lined up with one
hand and gently thread on the flare nut with the other.
Tighten the connection to the corresponding tightening torque
indicated in the table below.
Nominal diameter
mm
ø6.35
ø9.53
ø12.7
ø15.88
ø19.05
ø22.2
ø25.4
ø28.6
C A U T I O N
• Secure the fixed connection with a suitable wrench and use a torque wrench to tighten the flare nut on the
threaded connections.
• Do not exceed the torque value indicated in the table. The fitting can become misshapen and the connection
may leak.
¿ Refrigerant pipe insulation
The refrigerant circulates through the pipes at a very low temperature (several degrees below zero, depending on the time
of year and the installation). The difference in temperature with the ambient air is extremely large and causes two significant
phenomena to be taken into account:
• Cold irradiation along the entire pipe.
• Condensation of the humidity in the surrounding air.
Actually, cold irradiation is the temperature gain experienced by the gas, as when it circulates under pressure and at such
low temperatures along the inside of the pipes, it is actually liquid and obtains the outdoor temperature (boiling at a very
low temperature) to turn into gas.
As a result of the temperature gain (although it is actually perceived as cold emission), it loses its capacity to cool and the
system does not perform as expected. Furthermore, the humidity in the surrounding air condenses on the pipe and the
greater the temperature difference and the longer the pipe, the more water is produced.
In view of this, the refrigerant pipes must be fitted with a suitable insulation system that prevents the increase in temperature
of the refrigerant and the subsequent loss of energy and the condensation of water along the entire pipe.
Refrigerant pipes must always be separately insulated, using closed cell insulation foam designed especially for
refrigeration. This insulation foam, supplied by the installer, can be obtained in different formats. The most common is in
the form of sheets and rolls of tubes of different diameters.
Furthermore, all connections between the different sections of insulation tubes must be reinforced with adhesive tape of
the same characteristics.
Once all of the unit installation and adjustment work is complete, all threaded joints and valves must also be covered with
adhesive tape.
40
SMGB0065 rev. 1 - 12/2010
Inches
1/4
3/8
1/2
5/8
3/4
7/8
1
1-1/8
Tightening torque
20 Nm
40 Nm
60 Nm
80 Nm
100 Nm
–
–
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