BoilerFaultCodesTechnical description
OpenTherm communication error (caused by frost thermostat override)
What causes this fault?
This fault happens when the boiler loses its digital connection with the external heating controllers. The most common cause is a conflict created when an external frost thermostat is triggered, which physically breaks the communication loop to prioritize protecting your pipes. It can also be caused by loose wiring or a failing interface board within the control panel.
This error is significantly more common during periods of extreme cold when external frost protection devices are most likely to activate.
DIY fix possible
Check if any external frost thermostats or timers are set too low.Ensure your thermostat batteries aren't dead.Reset the boiler using the reset button on the control panel.
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