R-Pro › Field cases › Air conditioning
Water Dripping from Indoor Unit / Poor Drainage
Likely causes
Clogged condensate drain line — slime, algae, or dust
Check: Pour water into drain pan and check if it flows out. No flow at drain outlet = blockage. Use flashlight to check for slime buildup inside drain pan.
What to do: 1) Pour 50°C water into drain line to soften slime. 2) Vacuum suction or blow compressed air (0.3 MPa) from outlet end. 3) Pour vinegar + baking soda mix, wait 15 min, then flush. Preventive cleaning every 3 months recommended.
Faulty condensate pump
Check: Fill drain pan with water and check if pump starts automatically. Manually lift float switch to test pump operation. Verify pump power supply voltage (typically 220VAC).
What to do: Clean float switch of debris → retest. If still not operating after cleaning, replace pump unit (verify same head height and flow specs). Also check impeller for blockage.
Evaporator coil freezing — refrigerant shortage or clogged filter
Check: Visually check indoor unit air filter for blockage. Measure suction pressure with low-side gauge (R-410A cooling below 0.5 MPa = freezing risk). Measure indoor unit intake air temperature — below 12°C is freezing condition.
What to do: If frozen: immediately stop compressor, run fan-only mode to force thaw — natural thawing risks damaging stored goods. Using a 3kW heat gun or steam gun can shorten thaw time to 30–60 minutes. After thawing: clean air filter and check refrigerant charge. If refrigerant low, detect leak then recharge.
Cracked or improperly sloped drain pan
Check: Remove pan and visually inspect for cracks. Check pan slope with spirit level — must slope at least 1/100 toward drain outlet. After prolonged shutdown, check for standing water in pan.
What to do: Crack: temporary repair with epoxy resin is possible, but replacement recommended for PVC pans. Improper slope: re-adjust indoor unit bracket or insert wedges under pan to achieve proper slope.
Preventive drain line cleaning every 3 months is best practice. High-humidity environments (cold storage ante-rooms, laundromats) require monthly cleaning. If dripping comes from the discharge grille direction, likely meltwater from coil ice.
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