BoilerFaultCodes 34:0 Low
Boiler Fault Code 34:0
Also written as 340 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 34:0 appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler is receiving a constant request for heat from an external control or thermostat, causing all the pumps to run continuously. (As reported on Viessmann Vitodens 222-F)
Pick your boiler brand for the 34:0 fix
Source
Information for the 34:0 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026