BoilerFaultCodes.com

Saunier Duval Isotwin Condens Fault Codes

Combi Natural GasLPG 30-35 kW 2010-present
GC Number: 47-920-25

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Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Most common fault codes

F1
Your boiler is unable to safely light the flame needed to provide heating and hot water.
May be DIY safe · £100-£350
F4
Your boiler is unable to safely light the flame needed to provide heating and hot water.
May be DIY safe · £100-£350
F5
Your boiler has switched itself off because it has reached an unsafe temperature to protect the internal components from damage.
May be DIY safe · £120-300

All 23 fault codes

Code Severity Plain English
F1 High Your boiler is unable to safely light the flame needed to provide heating and hot water.
F4 High Your boiler is unable to safely light the flame needed to provide heating and hot water.
F5 High Your boiler has switched itself off because it has reached an unsafe temperature to protect the internal components from damage.
F6 High Your boiler has detected a problem with the sensor that monitors the temperature of the water heading to your radiators, causing the system to shut down for safety.
F7 High Your boiler has detected a problem with the sensor that monitors hot water temperature, which typically means you will have little or no hot water.
F8 High Your boiler's temperature sensor for the hot water storage tank has developed a fault, meaning the system cannot safely monitor or heat your hot water.
F9 High Your boiler has detected an issue with the sensor that monitors water pressure, which means it cannot verify if there is enough water to run safely.
F10 High Your boiler has detected a problem with the sensor that monitors the temperature of the water returning to the unit, which has caused the heating to stop working.
F11 High Your boiler is having trouble communicating with its control panel, which means it isn't receiving the instructions it needs to provide heating or hot water.
F12 High Your boiler's internal computer has lost communication with the control panel or display, preventing the system from operating.
F13 High Your boiler's internal computer has lost communication with its electronic components and needs a professional reset or repair.
F14 High Your boiler has shut down because the water inside the central heating system has reached an unsafely high temperature.
F16 Emergency Your boiler is still detecting a flame even after it has been told to turn off, which is a safety concern that requires a professional inspection.
F17 High Your boiler has stopped working because the electrical power coming from your home's mains supply is too low for it to run safely.
F18 High Your boiler's control panel and the internal computer are having trouble communicating with each other, meaning the display may not work or respond to your commands.
F19 High Your boiler has lost its connection to the sensor that monitors heating temperature, so it has stopped running as a safety precaution.
F20 High Your boiler's internal computer parts are having trouble communicating with each other, causing the system to shut down for safety.
F23 High Your boiler has sensed that water is not moving through the system properly, which is causing it to shut down to prevent overheating.
F24 High Your boiler has stopped working because the water returning from your radiators has become too hot, which usually means the water isn't circulating properly through the system.
F25 High Your boiler has detected that the water temperature is rising too quickly, which usually means the water isn't flowing through the system properly.
F26 High Your boiler has detected that the water is getting hot too quickly or the temperature difference between pipes is too wide, often caused by poor water flow.
F28 High Your boiler has detected that its temperature sensors are giving conflicting readings, which has caused it to stop working for safety.
F29 High Your boiler has shut down because a safety component has detected that the internal temperature reached a level high enough to potentially damage the system.

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