Alarm Z2 heat transfer fluid in sensor TC0 faulty

What does 5218 mean?

The Heat Pump has detected a fault with the heat transfer fluid inlet sensor (TC0) for zone 2. This alarm occurs after multiple short circuit or failure warnings for sensor TC0 over a short period.

• Faulty heat transfer fluid inlet sensor TC0 or its signal cable.
• Loose screw terminal connection for the sensor TC0 on the I/O board.
• Short circuit in the sensor TC0 or its signal cable.
• Internal I/O board malfunction.

Click steps to track your progress.

1. 1

   Visually inspect the sensor TC0's cable and its connection point to the Heat Pump for any signs of damage or dislodgement.

2. 2

   Ensure that any accessible screw terminals for sensor TC0 on the control board are snug (do not overtighten).

3. 3

   Power cycle your Heat Pump by turning off the dedicated circuit breaker for at least 30 seconds, then turning it back on.

4. 4

   If the alarm persists, contact a qualified Bosch service technician for further diagnosis and potential component replacement.