BoilerFaultCodesKeston E34 Fault Code
The Keston E34 fault code means: your boiler has stopped working because it isn't receiving enough electricity from your home's power supply to run safely.. It appears on 9 Keston models in our database.
Technical description: Mains supply voltage < 180V - There may be a problem with your power supply
What causes the Keston E34 fault?
This fault occurs when the electrical voltage entering the boiler drops below a safe operating level of 180V. The most common reason is a fluctuation or brownout in the local regional power grid, though it can occasionally be caused by a fault within the boiler's internal control board after a power surge.
This fault is slightly more common during winter or extreme heatwaves when the national grid is under heavy load, causing temporary dips in local supply voltage.
DIY fix possible
Check if other appliances in your home are flickering or underperformingEnsure your fuse box / consumer unit has not partially trippedContact your electricity network provider to see if there is a brownout or power fluctuation in your area
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Keston models that show the E34 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Keston E34 fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026