BoilerFaultCodesViessmann 176 Fault Code
The Viessmann 176 fault code means: the boiler has stopped because the water it produces when it burns gas is not draining away properly, so it has backed up and shut itself down to stay safe.. It appears on 7 Viessmann models in our database.
Technical description: Condensate backup in the heat cell
DIY fix possible
Turn the boiler off at its on/off switch and at the fused spur or isolator, then wait about 10 minutes for it to cool.Find the white plastic condensate pipe running from the boiler to an outside drain, and check it for ice, leaves, debris or a blockage. Gently clear any blockage you can reach and pour a kettle of lukewarm water through the pipe to test the flow.If the boiler has a condensate trap, place a bucket underneath, then carefully unscrew the trap cover and remove any sludge or debris. Refill the trap with water until it overflows slightly, then refit the cover.Restore power, switch the boiler back on and reset it using the reset button or the method in the user manual. If the code returns, or you see water leaking from the boiler, switch it off and call a Gas Safe registered engineer.
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Viessmann models that show the 176 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 176 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026