BoilerFaultCodes 20 High
Boiler Fault Code 20
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code 20 appears across 29 boiler brands and 156 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has detected an electrical fault with a sensor that monitors the water temperature flowing into your heating system, leading it to shut down for safety. (As reported on Viessmann Vitodens 200-W)
Pick your boiler brand for the 20 fix
Alpha 20 23 models Atag 20 9 models Atmos 20 4 models Baxi 20 18 models Biasi 20 4 models Chaffoteaux 20 5 models Daikin 20 3 models Dimplex 20 2 models ECA 20 1 model Ferroli 20 4 models Gledhill 20 1 model Glow-worm 20 10 models Halstead 20 5 models Heatline 20 3 models Ideal 20 3 models Intergas 20 11 models Main 20 7 models Malvern 20 2 models Maxol 20 1 model Navien 20 1 model Potterton 20 8 models Saunier Duval 20 7 models Servowarm 20 1 model Sime 20 2 models Unical 20 2 models Viessmann 20 9 models Vokera 20 6 models Warmworld 20 1 model Worcester Bosch 20 3 models
Source
Information for the 20 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