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Saunier Duval — Isomax
Select a fault code
Fault Codes
F20Safety thermostat tripped🔧 Engineer Required
Primary circuit overheated and safety limit triggered.
F22Low water pressure🔄 Try Reset
System pressure below minimum operating level.
F28Ignition failure🔄 Try Reset
Gas supply or ignition system fault — boiler failed to light.
F36Fan speed fault🔧 Engineer Required
Fan not reaching correct operating speed.
F49eBUS communication fault🔧 Engineer Required
Communication error on eBUS control wiring.
F75Pump or pressure sensor fault🔧 Engineer Required
Pump failure or pressure differential sensor fault.
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Prices shown are indicative — actual cost depends on your boiler age and policy type.
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Gas Emergency
🚨 0800 111 999
Free, 24/7 — if you smell gas
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