BoilerFaultCodesRavenheat E25 Fault Code
The Ravenheat E25 fault code means: your boiler has detected that the water inside the main heating unit has frozen due to extremely cold temperatures, preventing it from operating.. It appears on 9 Ravenheat models in our database.
Technical description: Main heat exchanger frozen
What causes the Ravenheat E25 fault?
This fault occurs when the temperature sensors inside the boiler detect that the water within the heat exchanger has dropped low enough to freeze. The most common reason is that the boiler is located in an unheated area, such as a garage or loft, without adequate insulation or frost protection during a severe cold snap.
This fault is exclusively seen during the winter months when external temperatures drop below freezing for extended periods.
DIY fix possible
Check if any external condensate pipes are frozen and thaw them with warm (not boiling) water.Increase the room thermostat setting to encourage movement in the system.Ensure the boiler is located in a draft-free area and keep the heating on a low constant setting during cold snaps.Reset the boiler once the unit has thawed out.
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Gas Safe Register →Ravenheat models that show the E25 fault code
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Source
Ravenheat E25 fault code information on this page is sourced and cross-checked against the official Ravenheat service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026