Filter Drier Clogged — 3°C+ temperature drop across drier

Question

Accepted Answer

Desiccant breakdown → clogs the mesh screen. Check: Measure pipe surface temp before and after drier (contact or IR). ΔT ≥ 3°C confirms clogging; ≥5°C is severe. Frost/condensation downstream = significant pressure drop. Also check liquid-line sight glass for bubbles and yellow moisture indicator What to do: Close service valves, recover refrigerant → replace drier (follow flow-direction arrow; liquid-line type), purge with nitrogen at 0.1–0.2 bar during brazing to prevent oxidation → vacuum to 500 micron for 30 min → after restart, reverify ΔT (≤1°C = normal). Size drier capacity equal to or greater than refrigerant charge Foreign debris in piping — metal burrs, solder slag, scale. Check: Inspect sight glass for particles/cloudiness; during replacement, cut open old drier and visually examine debris color/particles (metal = shiny, oxide = black). Ask about recent piping work or brazing What to do: After recovery, flush piping with nitrogen (pressurize to 5 bar, open low side to blow out, repeat 2–3 times) or with dedicated flushing solvent. For new installs, ream pipe ends and blow clean + cap with nitrogen fill before assembly. Consider adding an inline filter-strainer Drier past service life — not replaced for 2+ years or after system opening. Check: Check install-date label (often Sharpie-marked) or service logbook. Over 2 years, or any past system opening without replacement → due. In harsh conditions (humid, hot, high runtime), 1-year interval is recommended What to do: Keep end caps on new drier until install (prevents moisture absorption); unseal only within 30 min of installation. After install, mark install date and next-due date (2 years later) on label with permanent marker. Arrow MUST match refrigerant flow direction Refrigerant oil degraded → sludge deposits in drier core. Check: Check oil color (normal = clear amber; black/brown/cloudy = degraded); acid test strip (yellow-to-red = acidic). Cut-open drier reveals dark sludge or metal fines — combined with bad oil, suspect compressor burnout What to do: Recover all refrigerant → flush system (R-141b alternative or dedicated solvent) → drain oil → refill with same type POE/mineral per spec → install acid-scavenging drier (Catch-All/BFK type) → vacuum 500 micron 30 min → after 24 hrs run, remeasure drier ΔT and oil acidity. If compressor burnout signs, consider compressor replacement too Excess moisture in refrigerant → desiccant fully saturated and hardened. Check: Check moisture indicator in sight glass — green normal, yellow = excess moisture. Suspect prolonged system openings or inadequate evacuation in past. If replacement desiccant feels hard under finger pressure, saturation is confirmed What to do: After replacement, deep vacuum to ≤500 micron for 30+ min, then hold test (rise ≤100 micron in 15 min). Use fresh vacuum pump oil, short high-quality vacuum hoses, and a micron gauge for accurate readings. Old refrigerant may carry moisture + acid — if suspect, charge with virgin refrigerant

Filter Drier Clogged — 3°C+ temperature drop across drier

Likely causes

Desiccant breakdown → clogs the mesh screen

Foreign debris in piping — metal burrs, solder slag, scale

Drier past service life — not replaced for 2+ years or after system opening

Refrigerant oil degraded → sludge deposits in drier core

Excess moisture in refrigerant → desiccant fully saturated and hardened

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