Alarm Heat Pump board Z1 disconnected

What does 5266 mean?

The Heat Pump control board for zone 1 has lost communication with the indoor unit (tower). This alarm is triggered after multiple warnings or a prolonged communication failure via the CAN bus.

• Poor or loose connections of the CAN bus cables on the installer board or I/O board.
• Damage or failure of the CAN bus cable between the tower and the Heat Pump.
• Incorrect type of CAN bus cable used.
• CAN bus cable routed too close to power supply cables, causing interference.
• Incorrect or missing earthing of the CAN bus cable shield.

Click steps to track your progress.

1. 1

   Inspect all visible CAN bus cable connections for your Heat Pump to ensure they are securely seated and undamaged.

2. 2

   Verify that the CAN bus cable is routed separately from any high-voltage power supply cables, maintaining a distance of at least 100 mm (4 inches) to avoid interference.

3. 3

   Power cycle the Heat Pump by switching off its circuit breaker for 30 seconds, then turning it back on.

4. 4

   If the alarm continues, contact a qualified Bosch service technician to check cable integrity and system grounding.