R-Pro › Field cases › Air conditioning
Frozen Evaporator — indoor coil blocked by ice buildup
Likely causes
Severely clogged air filter or indoor coil → insufficient evaporator airflow
Check: Inspect filter and coil — if light barely passes through filter, confirmed clogged; check coil for ice and dust. Discharge airflow below 50% of normal. If fan motor is spinning normally, it's an airside issue
What to do: 1) Stop cooling immediately; turn fan OFF (running the fan slows thaw — less heat gets into the ice). 2) Cut power, protect drain pan with plastic sheet, place bucket below. 3) **Force-thaw with 3kW heat gun or steam cleaner — done in 30 min to 1 hr.** Steam gun is fastest. 4) Verify drain hose is clear (meltwater must drain). 5) After thaw, clean/replace filter and wash coil with no-rinse cleaner. 6) Before restart, verify superheat 5–8°C; if not, check charge and TXV. **Do NOT wait for natural thaw — spoils stored contents and halts business**
Low refrigerant → evaporating temperature drops well below 0°C
Check: Measure low-side gauge — R-410A normal 7–8 bar (evap 5–7°C); below 5 bar means evap drops below −5°C causing ice. Persistent bubbles in sight glass + lukewarm discharge air = leak confirmed
What to do: After thaw → scan all flare joints, service valves, brazed joints with electronic detector → re-flare/re-braze leak → recover refrigerant fully → evacuate ≤500 micron for 30 min → weigh in exact nameplate charge. No top-offs
Indoor fan motor running slow or stopped — no airflow = coil ices over
Check: Inspect fan motor visually and by ear — if not spinning or noisy, suspect bearings/capacitor. Measure current (±20% off rating = faulty), capacitor value (within ±10% of label = OK). For DC inverter fans, also check board signal
What to do: If capacitor is bad, replace with same μF/voltage. Bearing noise = replace motor (match AC shaded-pole vs. BLDC). Check blade for debris/deformation. If dust stopped it, clean blade and motor before restart
Long runtime at very low setpoint (≤18°C) in cool ambient
Check: Check remote setpoint — if set to ≤18°C while ambient drops below 20°C overnight. Ask user about usage pattern (all-night operation?)
What to do: Recommend setpoint 22–26°C; enable sleep timer or auto-off. Use Auto mode when ambient is cool. Except for industrial showcases/server rooms, sustained 18°C operation is unnecessary
Freezing up 2+ times almost certainly means a leak. If you just thaw and leave, callback within days. After thawing, always finish low-side pressure/superheat/leak check before leaving. On site, one heat gun is 10x faster than the fan.
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