Which component should be replaced during service to prevent moisture ingress?

• A. Filter drier
• B. Capillary tube
• C. Pressure relief valve
• D. Thermostat

Answer: (A)

Moisture control is the main idea here. When a refrigeration or air-conditioning system is opened or not fully evacuated, moisture can enter the refrigerant-oil circuit. The filter drier contains desiccants that actively absorb water and trap contaminants, preventing moisture from circulating and causing problems like acid formation, corrosion, and oil degradation. Replacing the drier during service ensures any moisture picked up during the work is removed before the system runs again.

The other components don’t serve this moisture-removal role: the capillary tube meters refrigerant flow, the pressure relief valve protects against overpressure, and the thermostat controls temperature.