BoilerFaultCodesYour boiler is working perfectly and is currently in standby mode because it has reached the desired temperature or your thermostat is turned down.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Standby (no demand for heat)
What causes this fault?
The 'O' code is not actually a fault, but the boiler's way of saying it is ready and waiting for a command. It occurs because the water inside the unit has reached the temperature set on your thermostat or the timer has reached an 'off' period. Once your home cools down or your heating schedule starts again, this code will automatically change as the boiler fires up.
This status is most frequently seen during spring and summer when the heating is used less often or turned off at the thermostat.
DIY fix possible
Check your room thermostat is turned up high enough to tell the boiler to run.Check your heating programmer or timer is set to an 'On' period.Ensure your TRVs (radiator valves) are open in the rooms you want to heat.
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A boiler cover plan would cover faults like O — no call-out fees, no surprises.
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