Brötje Furnaces Error Codes

A01

Burner does not ignite, furnace attempts start then locks out with A01 on display

Ignition failure / no flame detection

A02

Burner starts briefly then shuts down, A02 flame loss error displayed

Flame loss during operation

A03

Furnace locks out with A03, overheat condition, boiler very hot to touch

Safety temperature limiter (STB) tripped / overtemperature

A04

Display shows A04, no burner operation, boiler indicates low water pressure

Low system water pressure / water shortage

A05

Boiler shows A05, burner blocked, flue gas temperature too high

Flue gas overtemperature / blocked heat exchanger

A06

Display shows A06, boiler does not start, fan symbol may flash

Fan / air pressure fault

A07

Boiler shows A07, ignition sequence aborted, no fan pre-purge detected

Fan start failure / no air flow

A08

Error A08, boiler stops, display indicates flue gas sensor fault

Flue gas sensor open/short circuit

A09

Boiler locks out with A09, display may indicate flow sensor fault

Flow temperature sensor error

A10

Display shows A10, return temperature sensor fault, boiler stops

Return temperature sensor error

A11

Boiler shows A11, domestic hot water (DHW) sensor fault, no hot water

DHW temperature sensor error

A12

Error A12, boiler indicates outside sensor fault, weather-compensated control not working

Outdoor temperature sensor error

A13

Boiler shows A13, no communication with room controller or EMS bus device

Bus communication fault (e.g., ISR/EMS/eBUS)

A14

Display shows A14, boiler indicates gas type or parameter error after commissioning

Configuration / parameterisation fault

A15

Boiler shows A15, condensate fault, unit shuts down

Condensate drainage fault

A16

Error A16, boiler indicates flue blockage or differential pressure fault

Flue gas path obstruction

A17

Boiler shows A17, ionisation signal present without flame, immediate lockout

False flame detection / ionisation fault

A18

Error A18, boiler indicates pump fault, no circulation

Heating circulation pump failure

A19

Boiler shows A19, safety chain open, no burner operation

Safety interlock open (e.g., limit thermostat, flue thermostat, external safety)

A20

Display shows A20, gas pressure switch fault (if fitted)

Gas pressure supervision fault

E01

E01 displayed, general burner lockout, red fault LED lit

General burner fault (lockout)

E02

E02 displayed, overheat or limit thermostat trip

Overtemperature shutdown

E03

E03 displayed, flue gas safety device triggered

Flue gas safety / spillage fault

E04

E04 displayed, low water pressure lockout

Water pressure below minimum threshold

E05

E05 displayed, flow sensor or NTC error

Temperature sensor fault (flow)

E06

E06 displayed, return sensor or NTC error

Temperature sensor fault (return)

E07

E07 displayed, fan or air pressure fault

Insufficient air flow / fan error

E08

E08 displayed, ionisation fault / no flame signal

No flame detection

E09

E09 displayed, gas valve or gas train fault

Gas valve control error

E10

E10 displayed, communication error with expansion module or cascade controller

Module communication fault

Symptom

Boiler display is blank, no response to buttons, but mains power is present

No power to control board / control board failure

Symptom

Boiler display works but is very dim or segments missing

Display module degradation

Symptom

Boiler does not start when room thermostat calls for heat, but no fault code is shown

Control signal / thermostat wiring issue

Symptom

Boiler frequently cycles on and off with short run times, no error code

Short cycling

Symptom

Boiler pressure rises rapidly when heating and discharges water from safety valve

Expansion vessel failure / overpressure

Symptom

Condensate water dripping from flue joints or outside wall penetration

Condensate leakage from flue system

Symptom

Domestic hot water temperature fluctuates or is too hot/cold without error code

Unstable DHW control

Symptom

Furnace causes strong vibration transmitted into the flue or wall

Mechanical imbalance / mounting issue

Symptom

Furnace emits whistling or high-pitched noise during operation

Gas/air flow resonance or restriction

Symptom

Furnace makes loud banging or knocking noises when starting or stopping

Water hammer / thermal expansion noise

Symptom

Furnace runs but radiators stay lukewarm, long heat-up times, no error code

Insufficient heating output / undersized or modulating incorrectly

Symptom

Persistent smell of gas near the Brötje furnace, no error code

Gas leak

Symptom

Radiators on upper floors cold while lower floors heat normally

Air lock / circulation imbalance

Symptom

Soot deposits around flue terminal or on boiler casing, no immediate error code

Incomplete combustion / sooting

Symptom

Water leaking from the bottom of the Brötje furnace casing

Internal water leak