Buderus Logamax plus Boilers

The boiler's internal communication system (UBA 3 and BC10 basic controller) is experiencing a fault. The display flashes this code continuously if a problem is detected during or after the initial startup test. No heating or domestic hot water (DHW) will be available.

The boiler's return temperature sensor has measured a temperature higher than 203°F (95°C). This can affect the heating performance. This is a locking fault, meaning the boiler will try to resume normal operation once the temperature drops.

The flue gas sensor has detected an excessively high temperature in the exhaust gases. This is a safety measure to prevent damage to the boiler. No heating operation or domestic hot water (DHW) will be available until the fault is cleared.

There is a connection issue between specific contacts (78 and 50) on the UBA 3 installation base. This prevents the boiler from operating for heating or domestic hot water. As a locking fault, the boiler should attempt to clear itself.

The contacts for the flue gas sensor have a short circuit. This is a safety fault that prevents heating and domestic hot water operation. A manual reset is required after the cause is corrected.

The contacts for the flue gas sensor are open, indicating a broken connection. This is a blocking fault, stopping heating and domestic hot water. A manual reset is needed once the connection is restored.

The heating system's water pressure is below the minimum required level of 3 psi (0.2 bar). This will prevent both heating operation and domestic hot water. As a locking fault, the boiler will try to resume once pressure is restored.

After the burner starts, the flow temperature sensor has not detected any increase in the heating system's water temperature. This indicates a problem with heat transfer. As a locking fault, the boiler will try to clear itself.

The flow temperature sensor has detected an excessively rapid increase in heating water temperature (over 40°F/s or 5°C/s). This is a safety lockout, often indicating insufficient water flow or an overheating condition. This is a locking fault.

The temperature difference measured between the flow temperature sensor and the return temperature sensor is more than 122°F (50°C). This indicates a problem with heat distribution or water circulation. This is a locking fault.

The boiler is not receiving a feedback signal from the pump, suggesting it's not operating correctly or there's a communication issue. This is a locking fault, and the boiler will attempt to self-correct.

The tacho signal, which monitors the fan's speed, has failed during the boiler's operation. This indicates the fan is not working as expected, affecting combustion and exhaust. This is a locking fault.

The boiler is not detecting sufficient airflow after a set period. This could be due to a blocked flue or a fan issue, and it prevents heating and domestic hot water. This is a blocking fault, requiring a manual reset.

The tacho signal from the fan is not detected during the boiler's startup or operation, indicating a fan issue. This prevents both heating and domestic hot water. This is a blocking fault requiring a manual reset.

The boiler's fan is running below its required speed. This can affect combustion and exhaust. Both heating operation and domestic hot water are unavailable. This is a blocking fault, requiring a manual reset.

The boiler's fan is operating at an excessively high speed. This can indicate a control issue or a sensor problem. Heating operation and domestic hot water are unavailable. This is a blocking fault, requiring a manual reset.

The flow temperature sensor has detected an extremely high temperature (over 221°F / 105°C) in the system. This is a critical safety shutdown to prevent damage. Heating and domestic hot water are stopped. This is a blocking fault.

There is no bridging cable detected between contacts 22 and 24 on the UBA 3 contact strip. This connection is essential for normal operation. Heating and domestic hot water are unavailable. This is a blocking fault.

The boiler's internal sensor test has failed, indicating one or more sensors are not responding correctly. This prevents heating and domestic hot water operation. This is a blocking fault, requiring a manual reset.

The safety temperature sensor has detected an extremely high flow temperature (over 266°F / 130°C). This is a critical safety shutdown. Heating and domestic hot water are stopped. This is a blocking fault, requiring a manual reset.

The contacts for the safety temperature sensor have either shorted or the sensor has detected a flow temperature exceeding 266°F (130°C). This is a critical safety fault, preventing heating and domestic hot water. This is a blocking fault.

The contacts for the safety temperature sensor have been interrupted, indicating an open circuit or loose connection. This safety fault stops heating and domestic hot water. This is a blocking fault, requiring a manual reset.

The contacts for the safety temperature sensor have shorted. This is a safety fault that prevents heating and domestic hot water. This is a blocking fault, requiring a manual reset.

The contacts for the safety temperature sensor have been interrupted, indicating an open circuit or loose connection. This safety fault stops heating and domestic hot water. This is a blocking fault, requiring a manual reset.

After four attempts to ignite, the boiler still detects an insufficient ionization current. This indicates a persistent problem with the burner lighting correctly, preventing heating and domestic hot water. This is a blocking fault, requiring a manual reset.

An ionization current is still being measured even after the burner has shut down. This suggests gas is still burning or a sensor is faulty, posing a safety risk. Heating and domestic hot water are unavailable. This is a blocking fault.

The system has detected an insufficient ionization current while the burner should be operating normally. This means the flame is not stable or has gone out during operation. This is a blocking fault, requiring a manual reset.

The boiler has detected an insufficient ionization current during its normal operating phase, meaning the flame is not stable or has failed. This stops heating and domestic hot water. This is a blocking fault, requiring a manual reset.

The ionization current is excessively high, which can indicate a fault with the flame sensing or control system. Heating and domestic hot water are unavailable. This is a blocking fault, requiring a manual reset.

The boiler's power supply was interrupted while it was already experiencing a locking fault. This has now escalated to a blocking fault, stopping all heating and domestic hot water. This requires a manual reset.

There was a brief interruption in the boiler's power supply. This can disrupt its operation and lead to a blocking fault, stopping heating and domestic hot water. This requires a manual reset.

The boiler's UBA 3 control unit is identified as defective, leading to a complete shutdown of heating and domestic hot water. This is a blocking fault, requiring a manual reset.

Either the UBA 3 or the KIM control unit within the boiler is defective. This critical internal component failure stops all heating and domestic hot water operation. This is a blocking fault, requiring a manual reset.

Either the UBA 3 or the KIM control unit within the boiler is defective. This critical internal component failure stops all heating and domestic hot water operation. This is a blocking fault, requiring a manual reset.

Either the UBA 3 or the KIM control unit within the boiler is defective. This critical internal component failure stops all heating operation. This is a blocking fault, requiring a manual reset.

Either the UBA 3 or the KIM control unit within the boiler is defective. This critical internal component failure stops all heating and domestic hot water operation. This is a blocking fault, requiring a manual reset.

Either the UBA 3 or the KIM control unit within the boiler is defective. This critical internal component failure stops all heating and domestic hot water operation. This is a blocking fault, requiring a manual reset.

The digital water pressure sensor is defective and generating a fault code. This will prevent both heating operation and domestic hot water. This is a locking fault, and the boiler will attempt to self-correct.

There is a communication problem with the BC10 basic controller, or the BC10 unit itself is defective. Settings from RCxx devices (external controls) will no longer be applied. This is a locking fault, and the boiler will attempt to self-correct.

The WM10 module is not available, or there is no communication with it. This could be due to incorrect connection, a defective module, or the module not being recognized by the RC-thermostat. Heating circuit pump 1 will activate continuously. This is a locking fault, and the boiler will attempt to self-correct.

This locking fault occurs when both RC20 and RC35 remote controls are set as Master controllers. Both controls are trying to manage heating circuit 1 and Domestic Hot Water (DHW), leading to incorrect operation of the heating system.

This locking fault means the heating circuit flow sensor has a short circuit, an interrupted connection, or is incorrectly connected or defective. The boiler cannot correctly factor in room temperature information, which affects heating optimization.

This locking fault indicates that the heating circuit flow sensor for heating circuit 2 has a short circuit, an interrupted connection, or is incorrectly connected or defective. The heating circuit pump 2 will operate based on preset values, and the mixer power is switched off.