A7 alarm, no domestic hot water production

Safety: Isolate power before removing covers or touching wiring.

• Locate the hot water sensor: On Nibe systems with an external cylinder, the sensor is usually inserted into a pocket on the cylinder. Check that it is fully inserted and not dislodged.
• Inspect wiring: Trace the sensor cable back to the Nibe control board. Look for cuts, crushed sections, or loose plugs. Reseat the connector firmly.
• Check for moisture: Moisture in the sensor pocket or junction box can cause faults. Dry the area and reseal if necessary.
• Reset alarm: Restore power and clear the A7 alarm via the control panel. If the temperature reading is unrealistic (e.g., -40°C or 250°C), the sensor is likely defective.

Replace the hot water sensor with a Nibe‑approved part if wiring is intact but the fault persists.