13. Cylinder Air Purge
Air is not good for A/C system because it is a non-condensable gas. It is possible to get inside the
cylinder during the proces of recovery of contaminated a/c system (system which leaks or not
properly evacuated).
To check the cylinder for air contamination, a technician should read the pressure on the
refrigerant in storage cylinder to see if it exceeds the maximum allowable pressure for a given
ambient temperature. If it does, there is air in the cylinder and needs to be purged (through
cylinder vapor valve).
First, measure the ambient temperature. Then read the cylinder pressure on rear gauge (13) and
compare it with the temperature pressure chart, affixed to the machine.
If the cylinder pressure is higher than the pressure/temperature chart, there are non-condensable
gases (air) in the cylinder.
- Disconnect the vapour hose from cylinder.
- Slightly OPEN cylinder vapour valve to purge the non-condensable gases (air) from the
cylinder to bring back the pressure to the recommended chart values.
Note: After recovery process it is normal that cylinder pressure is higher than the
pressure/temperature chart shows. Always read the cylinder pressure first thing in the
morning before operating the machine.
Example: Ambient temp. 20
o
C, the cylinder pressure should be 4.7 bar (68 PSI).
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