Hitachi RAS-(4-6)HVRNS2E - Three Principles on Refrigerant Piping Work; Suspension of Refrigerant Piping

3 Piping work and
refrigerant charge
54
SMGB0064 rev.0 - 08/2011
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 inltration of moisture or dust
during the refrigerant piping work.
Three principles Cause of failure Presumable failure Preventive action
1. Dry
Keep good dryness
• Water inltration due to
insufcient protection at pipe ends
• Dewing inside of pipes
• Insufcient vacuum pumping time
Icing inside tube at ex. valve
(Water choking)
+
Generation of hydration and oxidation
of oil
↓
Clogged strainer, etc., insulation failure
and compressor failure
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
2. Clean
No dust inside of
pipes
• Inltration of dust or other through
the pipe ends.
• Oxidation lm during brazing
without blowing nitrogen.
• Insufcient ushing by nitrogen
after brazing
Clogging of expansion valve, capillary
tube and lter
→Oxidation of oil
→Compressor failure
↓
Insufcient cooling or heating com-
pressor failure
Pipe Protection
1 Mounting Caps
2 Taping
3 Pinching
↓
Flushing
3. No leakage
No leakage shall exist
• Brazing failure
• Failed aring work and insufcient
torque of squeezing are
• Insufcient torque of squeezing
anges
Refrigerant shortage
→Performance decrease
→Oxidation of oil
→Overheating of compressor
↓
Insufcient cooling or heating com-
pressor failure
Careful Basic Brazing Work
↓
Basic Flaring Work
↓
Basic Flange Connecting Work
↓
Air Tight Test
↓
Holding of Vacuum
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 x the piping to wall or ceilings use suspension and clamping systems as shown in the following gure.