System Accessories & Components
Filter driers, sight glasses, receivers, accumulators, oil separators, solenoid valves, and check valves.
- Explain the purpose and location of filter driers in a refrigeration system
- Interpret sight glass indicators for moisture and charge level
- Describe the function of receivers, accumulators, and oil separators
- Identify the purpose and operation of solenoid, check, and service valves
Leçon 1
Filter Driers & Sight Glass Indicators
Filter Drier Function
The filter drier has two purposes: it removes moisture and filters solid contaminants from the refrigerant. Moisture in a refrigeration system combines with refrigerant and oil to form acids that damage compressor valves, bearings, and windings. The filter drier contains a desiccant (typically molecular sieve) that adsorbs moisture.
Filter Drier Types
A liquid line filter drier is installed in the liquid line between the condenser/receiver and the metering device. It protects the metering device from contaminants. A suction line filter drier (burnout drier) is installed temporarily after a compressor burnout to capture acids and carbon particles. The suction drier must be removed or replaced after cleanup is complete to avoid excessive pressure drop.
Sight Glass / Moisture Indicator
The sight glass is installed in the liquid line after the filter drier. It serves two purposes:
- Bubble detection - Bubbles in the sight glass indicate low charge, a restriction upstream, or excessive subcooling loss
- Moisture indication - The color-changing element shows system moisture level
Green / Dry
Moisture level: Safe
Action: No action needed
Yellow / Caution
Moisture level: Approaching limit
Action: Monitor, may need drier change
Brown / Wet
Moisture level: Excessive
Action: Replace filter drier immediately
Sight Glass Bubbles
Bubbles in the sight glass do not always mean low charge. A restriction in the liquid line upstream of the sight glass, a dirty filter drier, or insufficient subcooling can also cause bubbles. Always check subcooling before adding refrigerant.
The filter drier removes moisture and contaminants from the liquid line. A sight glass showing bubbles may indicate low charge, but always verify by checking subcooling first. A brown/wet moisture indicator means the drier must be replaced immediately.