Purging of air from system

Purging of air from system

Occasionally due to improper installation or maintenance procedures, a unit will not be completely evacuated, or oir will be allowed to enter the system after evacuation. The non-condensable gases will exert their own pressures in addition to refrigerant pressure, and will result in head pressure considerably above the normal condensing pressure.

Aside from the loss of capacity resulting from the higher head pressure, the presence of air in the system will greatly increase the rate of corrosion and can lead to possible carbon formation, copper plating, and/or motor failure.

As a temporary measure, it may be possible to purge refrigerant from the top of the condenser while the unit is not operating, and blow out any air trapped in the condenser. However, it is almost impossible to purgue all of the air out of the compressor cranckase, and air may also trap in the receiver. If it is discovered that air has been allowed to contaminate the system, the refrigerant should be removed, and the entire unit completely evacuated with an efficient vaccum pump.

Liquid Line Filter-Drier

On all transport refrigeration systems. because of the uncertainties of installation and service, a liquid line filter-drier is essential. It is recommended that the filter-drier be oversized by at least 50% for the refrigerant charge because of the many opportunities during field maintenace for moisture to enter the system. It should have flare connections for easy replacement.