Hitachi Econofresh, Service Manual

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3.4 Copper gas refrigerant pipe
3.4.1 Three principles on work with refrigerant pipes
The basic gas refrigerant pipe installation work must be carried out paying particular attention to avoid the infiltration of
humidity or dust while working with the refrigerant piping. Otherwise, rust may appear inside the system or the units and
cause serious faults.
Therefore, all work carried out on the copper pipes for gas refrigerant must follow the three principles described below.
Principle Cause of the fault Possible fault Preventive measure
1. Absence of humidity
Ensure the atmosphere
remains totally dry
• Water infiltration due to
insufficient protection on
the ends of the pipes.
• Condensation on the
inside of the pipes.
• Insufficient vacuum.
Ice on the inside of the pipe,
on the expansion valve
(water obstruction)
+
Absorption of oil humidity
and oxidation
↓
Filter clogging, insulation
and compressor fault
Pipe protection:
1. Seal the ends of the pipes.
2. Protect and insulate the
ends of the pipes.
↓
Wash
↓
Vacuum dry
(*)
2. Cleaning
Absence of dust on the
inside of the piping
• Dust or other elements
entering the ends of the
pipes.
• Film of rust formed
during brazing without
nitrogen injection.
• Insufficient nitrogen
wash after brazing.
Expansion valve, capillary
tube and filter clogging.
Oil oxidation.
Compressor fault
↓
Compressor fault,
insufficient cooling or
heating
Pipe protection:
1. Fit caps to the ends of the
pipes.
2. Protect and insulate the
ends of the pipes.
↓
Wash
3. Absence of leaks
There must be no leaks
• Brazing fault.
• Flaring fault and
insufficient torque.
• Insufficient torque on
compressor connectors.
Lack of refrigerant
Drop in performance
Compressor fault
Oil oxidation.
↓
Compressor overheating
Carry out basic brazing work
carefully
↓
Carry out basic flaring work
carefully
↓
Carry out basic connection
work carefully
↓
Airtight test
↓
Preserving of vacuum in the
installation
(*)
One gram of water becomes approximately 1000 l of steam at 1 Torr. (1 Torr = 1 mmHg = 133.32 Pa). Therefore, a long
time must be spent on vacuum work using a small pump.
3 Piping work and
refrigerant charge
82
SMGB0063 rev. 1 - 10/2010