Moisture Damage: Acid Formation
When moisture enters a refrigeration system, it reacts with the refrigerant at high temperatures to form hydrofluoric acid (HF) and hydrochloric acid (HCl). These powerful acids attack metal surfaces throughout the system, causing pitting, corrosion, and eventual component failure. In systems using HFC refrigerants with POE oil, moisture also breaks down the oil itself through a process called hydrolysis, further accelerating acid formation. This acid damage is cumulative and irreversible.
Moisture reacts with refrigerant to form hydrofluoric (HF) and hydrochloric (HCl) acids that corrode metal surfaces and destroy system components.
Moisture Damage: Freeze-Ups & Copper Plating
Moisture in a refrigeration system can freeze at the metering device orifice, where the sudden pressure drop causes temperature to plunge. This ice blockage restricts or completely stops refrigerant flow, causing the system to lose cooling capacity. Additionally, the acids formed by moisture dissolve copper from the tubing and deposit it onto steel components such as compressor valve plates and bearings -- a phenomenon called copper plating. Copper plating causes valves to leak and bearings to seize.
Moisture freezes at the metering device, blocking refrigerant flow. Acids dissolve copper from tubing and plate it onto compressor valve plates and bearings.
Non-Condensable Gases
Non-condensable gases, primarily air, cannot change phase within the system's operating pressures. They accumulate in the condenser and take up space that should be used for condensing refrigerant. This raises the head (discharge) pressure above normal levels, forcing the compressor to work harder. The result is reduced system efficiency, higher energy consumption, elevated operating temperatures, and shortened compressor life. Higher than normal discharge pressure is the key diagnostic indicator of non-condensables in the system.
Non-condensable gases raise head pressure above normal, reduce efficiency, and increase energy consumption. Higher than normal discharge pressure is the key symptom.
Desiccants & Filter-Driers
Detecting Moisture Contamination
Several signs indicate moisture contamination in a refrigeration system. An acid test of the oil will show positive results. The metering device may become intermittently restricted as ice forms and melts. A sight glass with a moisture indicator will change color (typically from green to yellow). Copper plating may be visible on compressor valve plates during teardown. If moisture contamination is confirmed, the filter-drier should be replaced, and a thorough evacuation should be performed after repairs.
Signs of moisture: positive acid test, intermittent metering device restriction, sight glass color change, and copper plating on valve plates.
Why We Evacuate Review
- Moisture reacts with refrigerant to form hydrofluoric (HF) and hydrochloric (HCl) acids that corrode system components.
- Moisture freezes at the metering device orifice, blocking refrigerant flow and causing loss of cooling.
- Acids dissolve copper from tubing and deposit it on compressor valve plates (copper plating), causing valve leaks and bearing seizure.
- Non-condensable gases raise discharge pressure above normal, reducing efficiency and increasing energy consumption.
- Desiccants (molecular sieve, activated alumina, silica gel) trap moisture inside filter-driers.
- Signs of moisture contamination include positive acid test, restricted metering device, sight glass color change, and copper plating.