The Daikin Altherma 7h fault code points to insufficient water flow in the heating circuit. Owners fix this by cleaning the strainer and confirming the circulation pump spins freely.
Additional checks on the flow sensor and air removal prevent recurrence without professional service calls. Monitor system pressure after each adjustment to ensure stable operation.
Daikin Altherma 7h Flow Sensor Triggers
The Daikin Altherma 7h code activates when the flow sensor detects inadequate circulation through the heat exchanger. This condition often appears during startup or after extended downtime when debris accumulates. Technicians first confirm the error by reviewing the controller display and noting any related pressure readings. The issue rarely stems from software alone and instead traces to mechanical restrictions in the loop. A structured review helps isolate the exact location before parts are ordered.
| Symptom | Primary Suspect | Difficulty 1-5 |
|---|---|---|
| Low flow error on startup | Blocked strainer | 2 |
| Pump runs but pressure drops | Air in circuit | 3 |
| Intermittent 7h code | Faulty flow sensor | 4 |
| No heat with normal pressure | Worn pump impeller | 5 |
Daikin Altherma 7h Strainer Pump Failures
Restricted water movement triggers the 7h code because the sensor requires a minimum flow rate to stay satisfied. Debris in the strainer or a seized circulation pump impeller accounts for most cases. Air pockets also interrupt flow and create false readings at the sensor. Corrosion on electrical connections to the pump can mimic a mechanical failure. Systematic isolation of each component prevents unnecessary replacement of functional parts.
Daikin Altherma 7h Strainer Flush and Air Bleed
Isolate power to the outdoor unit before any disassembly begins. Remove the front access panel and locate the strainer housing near the return line. Clean the strainer by flushing it under running water until all sediment clears. Reinstall the strainer and restore power to test flow. Bleed air from the highest point in the circuit using the manual vent valve until steady water emerges without bubbles. Verify pump rotation by listening for consistent operation after the test cycle starts.
Daikin Altherma 7h Flow Sensor Cleaning
The flow sensor sits inline after the pump and must register steady movement to clear the fault. Technicians remove the sensor connector and check for debris lodged against the paddle wheel. Clean the sensor housing with a soft brush if buildup appears. Reconnect the wiring and cycle the system to confirm the reading stabilizes above the minimum threshold. Persistent errors after cleaning indicate the sensor itself requires replacement with an exact match for the Altherma model.
Daikin Altherma 7h Air Bleed Procedure
Trapped air reduces effective flow volume and repeatedly trips the 7h code during operation. Start at the highest radiator or manifold point and open the bleed valve slowly. Attach a hose to direct water into a container while monitoring the pressure gauge. Continue until no air escapes and pressure holds steady between 1.5 and 2.0 bar. Repeat the process at secondary vents if the code returns after the initial bleed.
Daikin Altherma 7h Expansion Vessel Pressure Check
Correct pressure supports consistent flow through the entire loop and prevents the sensor from triggering. Check the expansion vessel charge with a tire gauge when the system is cold. Adjust the vessel pre-charge to 0.5 bar below the cold fill pressure if it has dropped. Top up the system through the fill valve while watching the gauge to avoid over-pressurization. Record the final cold pressure for future reference during seasonal checks.
Daikin Altherma 7h Flow Verification Cycle
Restore full power and run a complete heating demand cycle through the controller. Observe the flow rate reading on the display for at least ten minutes of continuous operation. Confirm the 7h code does not reappear and that supply and return temperatures track normally. Document the final pressure and sensor values for the service record.
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