Unknown
Ext’ Interlock Off on Keston Heat 55

Keston Heat 55 fault code Ext’ Interlock Off

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

What the manual says

Manufacturer manual

External Interlock Operated, Reset Interlock

From this model's manual
Verified against the Keston/Keston Heat 45 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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All 36 fault codes on the Heat 55

Seeing a different code? Every code this model can display, in one place.

167475767778798081828384858687888990BCC FaultCylinder Thermistor FaultError 20False Flame LockoutFan FaultFlame LossFlow/Flue Thermistor FaultFlow/Return ReversedFlue Thermistor FaultIgnition LockoutLow Mains VoltageLow Water PressureOutside Sensor FaultOverheat LockoutPCB FaultReturn Thmr FaultToo Many Resets

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