R-Pro › Field cases › Air conditioning
AC Drain Pipe Freeze — Winter Drainage Failure
Likely causes
Identify freeze location (exposed segments, trap area)
Check: Below 0°C ambient + outdoor exposed run = freeze risk. Feel hose: hard/cold = frozen. Trap (P or inverted) = stagnant water freezes first. Insulation typically ≥9 mm. When frozen, condensate may back up to ceiling.
What to do: Emergency defrost: pour warm water slowly (no boiling = PVC damage). Outdoor exposed = install self-regulating heat trace 30 W/m + 19 mm insulation. Trap area = add insulation. Korean Gangwon/central zones <5°C = heat trace required. Educate user: inspect at winter start.
Freeze = emergency dispatch but users often unaware. Off-season (Nov–Apr Korea) = recommend system OFF + drain hose empty. After thaw, inspect hose for cracks — freeze expansion may have caused them.
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