Buderus Logamax Plus GB172

Operating and Fault Indications Displayed on the Display

Fault Code	Working Code	Description
-A	208	The boiler is in the chimney sweep mode. After 15 minutes, the chimney sweep mode will be automatically deactivated.
-H	200	The boiler is in heating mode.
=H	201	The boiler is in DHW mode.
0A	202	Button lock active: the time interval for reactivating the burner has not yet been reached (Æ service function 2.3b).
0C	283	The burner start is in progress.
0E	265	The heat demand is lower than the boiler’s minimum heating power. The boiler operates in on/off mode.
0H	203	The boiler is in standby mode, with no heat demand.
0L	284	The gas valve is opening, the first safety time.
0U	270	The boiler is reaching high power.
0Y	204	The current supply temperature is higher than the set supply temperature. The boiler is turning off.
2E	357	The venting function is active.
2H	358	The protection against blocking the heating pump and the three-way valve is active.
2P	342	Speed growth limitation (gradient): too rapid temperature increase in DHW mode.
5H	268	The boiler is in a regulation system test.

Transient Faults

Fault Code	Working Code	Description	Method of Removal
0Y	276	The temperature on the supply temperature sensor is > 95 °C.	This fault message may appear without a fault if all radiator valves are suddenly closed. Check the operating pressure in the heating system. Fully open the service valves. Electrically connect the heating pump to the base controller BC25. Start the heating pump or replace it. Properly set the pump performance or characteristics and adjust to maximum power. Check the supply temperature and connection cable for interruptions or short circuits, replace if necessary.
2P	341	Gradual limitation: too rapid temperature increase in heating mode.	Check the operating pressure in the heating system. Fully open the service valves. Electrically connect the heating pump to the base controller BC25. Start the heating pump or replace it. Set the pump’s performance or characteristics correctly and adjust to the maximum power.
3A	264	Fan failure during operation.	Check and replace the fan connector cable or the fan if necessary.
3F	273	The burner and fan worked continuously for 24 hours and will be temporarily switched off for safety control.	–
4C	224	The exchanger temperature limiter or flue temperature limiter has been triggered.	If the transient fault persists for a longer period, it will change into a permanent fault.
4U	350	Supply temperature sensor defective (short circuit).	If the fault persists for a longer period, the fault code 4U and working code 222 will be shown.
4Y	351	Supply temperature sensor defective (interruption).	If the fault persists for a longer period, the fault code 4Y and working code 223 will be shown.
6A	227	Flame not confirmed.	After the 4th ignition attempt, the transient fault will become a permanent fault (non-transient).
6L	229	No ionization signal during burner operation.	The burner will restart. If the ignition attempt fails, the transient fault 6A will be shown, and after the 4th ignition attempt, the transient fault will become a permanent fault.
8Y	232	Thermal protection AT90 has been triggered.	Check the settings of the thermal protection AT90 sensor. Check the settings of the heating controller.
8Y	232	Thermal protection AT90 is defective.	Check the temperature sensor and connection cable for interruptions or short circuits, replace if necessary.
8Y	232	Missing bridge on the connection terminals for the external thermal protection AT90.	If the thermal protection is not connected, install the bridge.
8Y	232	Blocked thermal protection. Condensate pump failure.	Unblock the thermal protection. Check the condensate drainage. Replace the condensate pump.
EL	290	Damaged base controller BC25.	Replace the base controller BC25.

Non-Transient Faults

Fault Code	Working Code	Description	How to Fix
3C	217	Fan not working.	Check and, if necessary, replace the fan connector cable or the fan.
3L	214	Fan is turned off during the safety period.	Check and, if necessary, replace the fan connector cable or the fan.
3P	216	Fan is too slow.	Check and, if necessary, replace the fan connector cable or the fan.
3Y	215	Fan is too fast.	Check and, if necessary, replace the fan connector cable or the fan. Check the flue gas system, clean or repair if necessary.
4C	224	Temperature limiter of the heat exchanger or flue temperature has been triggered.	Check for interruptions or short circuits and, if necessary, replace the heat exchanger temperature limiter and the connection cable. Check for interruptions or short circuits and, if necessary, replace the flue temperature limiter and the connection cable. Check the operating pressure in the heating system. Check and, if necessary, replace the temperature limiter. Check the pump start-up, and if necessary, replace it. Bleed the boiler. Check the heat exchanger on the water side, and if necessary, replace it. For boilers with reverse cylinders in the heat exchanger: check if they are installed properly.
4U	222	Supply temperature sensor damaged (short circuit).	Check the temperature sensor and connection cable for interruptions or short circuits, replace if necessary.
4Y	223	Supply temperature sensor damaged (interruption).	Check the temperature sensor and connection cable for interruptions or short circuits, replace if necessary.
6A	227	Flame not confirmed.	Check the effectiveness of the protective conductor connection. Check if the gas valve is open. Check the gas pressure at the connection (Æ page 48). Check the electrical connection. Check the electrodes and cables, and replace if necessary. Check the flue system, clean or repair if necessary. Check the gas-to-air ratio, adjust if necessary. If using natural gas, check and replace the external gas flow protection (pressure switch) if necessary. For operation dependent on room air, check the “room connection” or ventilation/air intake openings. Clean the condensate siphon outlet. Remove the membrane from the fan inlet nozzle and check for cracks or contamination. Clean the heat exchanger. Check and replace the gas fittings if necessary. Correctly insert the KIM, replace if necessary. For two-phase networks (IT): install a 2 W resistor on the network connection of the printed circuit board.
6C	228	Flame detected despite the boiler being off.	Check the electrodes, and replace if necessary. Check the flue system, clean or repair if necessary. Check if the printed circuit board is wet, dry if necessary.
6C	306	Flame detected after the gas was turned off.	Check and replace the gas fittings if necessary. Clean the condensate siphon. Check the electrodes and connection cables, and replace if necessary. Check the flue system, clean or repair if necessary.
7L	261	Time error during the first safety time.	Replace the base controller BC25.
7L	280	Time error during the restart attempt.	Replace the base controller BC25.
9L	234	Gas valve coil or connection cable is damaged.	Check the wiring, replace if necessary. Replace the gas valve.
9L	238	Gas valve is damaged.	Check the wiring, replace if necessary. Replace the gas valve.
9P	239	KIM not recognized.	Correctly insert the KIM, replace if necessary.
EL	259	Damaged KIM or Logamatic BC25.	Replace the KIM. Replace the base controller BC25.

Faults not displayed on the screen

Boiler faults	How to fix
Too loud combustion noise; growling	Correctly insert the KIM, replace if necessary. Check the type of gas. Check the gas pressure at the connection. Check the flue system, clean or repair if necessary. Check the gas-to-air ratio in the combustion air and flue gases, replace the gas valve if necessary.
Flow noises	Set the correct performance or characteristic of the pump and adjust to maximum power.
Heating takes too long	Set the correct performance or characteristic of the pump and adjust it to maximum power.
Flue gas values are incorrect; too high CO levels	Check the type of gas. Check the gas pressure at the connection. Check the flue system, clean or repair if necessary. Check the gas-to-air ratio in the flue gases, replace the gas valve if necessary.
Poor, too hard ignition	Check the type of gas. Check the gas pressure at the connection. Check the electrical connection. Check the electrodes with cables and replace if necessary. Check the flue system, clean or repair if necessary. Check the gas-to-air ratio, replace the gas valve if necessary. For natural gas: check the external (additional) gas flow protection, replace if necessary. Check the burner, replace if necessary.
Domestic hot water has a bad smell or dark color	Perform a thermal disinfection of the domestic hot water circuit. Replace the protective anode.
Condensate in the air chamber	Install or replace the membrane in the mixing unit according to the installation instructions.
Function unavailable (display remains dark)	Check the electrical connection. Check the fuse, replace it if necessary.