Moisture in the system can be caused by condensation from moist air which has entered the system-via charging the system with wet refrigerant or poor grades of refrigerant oils, or from moisture on internal parts and/or leaks.
Internally wet charging hoses/gauges.
A plugged filter-drier will cause excessive pressure drop, resulting in flash gas.
Ice formation or wax restricting the flow of refrigerant may be indicated by a sudden rise in suction pressure after a shutdown, when the system warms up.
- To check while the system is running, use a heat gun to warm the TEV (this will melt the ice), and note the rise in the suction pressure.
- The heat gun will generally not melt the wax, this makes wax difficult to discover.
- Waxing can occur in low temperature units operating below -25°F evaporating.
- Waxing will usually liquefy and flow again near OOP or higher.
Moisture can be created from the air. Air with its free oxygen, may oxidize the oil and combine with the liberated hydrogen in the coil to form water.
Moisture can combine with refrigerants to form acids (excessive heat accelerates the acid formation).
- Acids will eat away at everything in contact, and eventually will cause system breakdown.
An effective way of eliminating moisture from a system is to properly dehydrate the system before charging, and to install ALCO liquid and suction line filter-driers
Replace as necessary.
Keep the refrigerant oil container sealed from the atmosphere at all times. Refrigerant oil has an attraction for moisture-if left open to the atmosphere, the oil will absorb the moisture rapidly.
Wax in the system may indicate that the wrong oil is being used. Recover/recycle the refrigerant, evacuate and recharge with clean, dry refrigerant and the proper refrigerant oil.