What happens
An obstruction, incorrect fall or unintended rise prevents water from leaving the indoor pan.
Typical symptoms
Indoor dripping during cooling, pan backup or leakage soon after installation.
Checks that distinguish this cause
Inspect the drain route, mounting level and outlet against the indoor unit manual. Perform its specified drain test; check whether accumulated ice is melting into the pan.
What can look similar
Condensation on exposed piping can drip outside a correctly draining pan.
Repair direction
Clear the verified obstruction and restore the permitted routing and cabinet mounting.
Verify the repair
Verify drainage under the prescribed test and a sustained cooling cycle without leakage.
Equipment-specific limits
Drain lift, hose routing, traps, vents and overflow wiring differ by indoor style and pump. Do not bypass overflow protection or assume a high-wall drain design suits a cassette.
Practice this diagnosis
This cause is a reference topic; it does not yet have a dedicated simulated call. Browse the practice board.
References and applicability
Original HVACSim explanations with manufacturer and instrument-maker references for further reading. These resources support the subject; their model-specific examples are not specifications for every system.
- Senville: R-454B model documentationSeparate installation and service documents for indoor styles and multi-zone generations.
- Haier: Arctic Next Gen service manualAW/1U EH2VHD model examples of inverter, motor, sensor and circuit diagnostics; obtain the installed model manual.
Editorial review: 2026-09-29. Verify the current manual for the installed model.