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Heating engineer · Brussels and Wallonia
Buderus error codes
The most common codes for Buderus Logamax plus GB172 and GB172i, with what they mean and what to do.
The boiler shows a two-character fault code (e.g. 6A) and, depending on the model, a three-digit operating code (227). After several failed resets the appliance locks (code 2980): only a professional can then unlock it.
System pressure too low (GB172i).
PressureCheck the pressure gauge. If it's too low, top up the water (if you know how) and bleed the radiators. If the pressure drops again, there's probably a leak: call us.
The flame isn't detected: after the 4th ignition attempt, the boiler locks out.
IgnitionCheck that the gas tap is open, then reset the boiler once. If the code comes back, don't keep trying: repeated resets can lock the appliance. Call us.
Flame signal lost during operation: the burner restarts.
TemporaryThe boiler restarts on its own once the cause is gone. If the code keeps coming back, call us for a check.
The mains power was interrupted.
TemporaryThe boiler restarts on its own once the cause is gone. If the code keeps coming back, call us for a check.
The heat exchanger or flue gas temperature limiter has tripped.
CirculationCheck the pressure and that the radiator valves are open. If everything looks fine and the code comes back, the water circulation needs checking (pump, bleeding, sensors): call us.
The heating pump isn't building pressure.
CirculationCheck the pressure and that the radiator valves are open. If everything looks fine and the code comes back, the water circulation needs checking (pump, bleeding, sensors): call us.
The temperature is rising too fast in heating mode.
CirculationCheck the pressure and that the radiator valves are open. If everything looks fine and the code comes back, the water circulation needs checking (pump, bleeding, sensors): call us.
Fan running too fast: the flue needs checking.
Flue · safetySwitch the boiler off and air the room. This code concerns the flue: call us. If a CO alarm goes off, or anyone has a headache or nausea, get everyone outside and call 112.
A flame is detected while the burner is off.
TechnicianA component or electronics fault: this needs a technician. Don't open the boiler; call us and give the code shown.
The fan has failed.
TechnicianA component or electronics fault: this needs a technician. Don't open the boiler; call us and give the code shown.
The fan is running too slowly.
TechnicianA component or electronics fault: this needs a technician. Don't open the boiler; call us and give the code shown.
Flow temperature sensor faulty (short circuit or open circuit).
TechnicianA component or electronics fault: this needs a technician. Don't open the boiler; call us and give the code shown.
Gas valve or its cable faulty.
TechnicianA component or electronics fault: this needs a technician. Don't open the boiler; call us and give the code shown.
Internal electronics fault.
TechnicianA component or electronics fault: this needs a technician. Don't open the boiler; call us and give the code shown.
This code isn't in the list: call us and give it to us, we'll tell you straight away what's going on.
Source: Buderus, Logamax plus GB172 installation manual (6720647778) and GB172i operating instructions (6721824729). Codes and how they're shown can differ between models: if in doubt, your appliance's manual applies.
First steps
- Write down the code shown: it saves us time.
- Check the pressure gauge.
- Check that the gas tap is open.
- Reset once. If the code comes back, call us.
Practical guides: Top up the pressure · Bleed a radiator · Reset the boiler
A breakdown, a question? Get in touch.
Call us or message us on WhatsApp. Or leave your number, with a photo of the boiler if you like: we'll call you back.
