Three Principles On Refrigerant Piping Work; Suspension Of Refrigerant Piping - Hitachi RAS-5HVRNM1E Service Manual

3 Piping work and
refrigerant charge

3.2.2 Three principles on refrigerant piping work

In case of using refrigerant R410A in the refrigeration cycle, the refrigeration oil should be of a synthetic type one.
In order to avoid oxidation, pay much careful attention to basic piping work control to avoid infiltration of moisture or dust
during the refrigerant piping work.
Three principles
• Water infiltration due to insufficient
protection at pipe ends
• Dewing inside of pipes
1. Dry
• Insufficient vacuum pumping time
Keep good dryness
• Infiltration of dust or other through
the pipe ends.
• Oxidation film during brazing
2. Clean
without blowing nitrogen.
No dust inside of pipes
• Insufficient flushing by nitrogen
after brazing
• Brazing failure
• Failed flaring work and insufficient
torque of squeezing flare
3. No leakage
• Insufficient torque of squeezing
No leakage shall exist
flanges

3.2.3 Suspension of refrigerant piping

Suspend the refrigerant piping at certain points and prevent the refrigerant piping from touching weak parts of the building
such as walls, ceiling, etc. (If touched, abnormal noises may occur due to the vibration of the piping. Pay special attention
in case of short piping length).
A. Fire-proof section treatment.
B. Indoor unit.
In order to fix the piping to wall or ceilings use suspension and clamping systems as shown in the following figure.
54
SMGB0060 rev. 1- 12/2010
Cause of failure
Generation of hydration and oxidation
Clogged strainer, etc., insulation failure
Clogging of expansion valve, capillary
Presumable failure
Icing inside tube at ex. valve
(Water choking)
+
of oil
↓
and compressor failure
tube and filter
→Oxidation of oil
→Compressor failure
↓
Insufficient cooling or heating
compressor failure
Refrigerant shortage
→Performance decrease
→Oxidation of oil
→Overheating of compressor
↓
Insufficient cooling or heating
compressor failure
Preventive action
Pipe protection
1 Pinching
2 Taping
↓
Flushing
↓
Vacuum Drying
• One gram of water turns into gas
(approx. 1000 lrs) at 1 Torn
• Therefore, it takes long time to
vacuum-pump by a small vacuum
pump
Pipe Protection
1 Mounting Caps
2 Taping
3 Pinching
↓
Flushing
Careful Basic Brazing Work
↓
Basic Flaring Work
↓
Basic Flange Connecting Work
↓
Air Tight Test
↓
Holding of Vacuum