My son's Raveheat combi condensing boiler has developed a strange
fault.

If he has the CH temperature set at high the boiler keeps cutting out
and the fault light comes on. If he turns the CH temperature down to
half it runs OK and does not cut out.

The HW runs OK.

Any pointers as to what might be causing this fault would be much
appreciated.

chudford wrote:
My son's Raveheat combi condensing boiler has developed a strange
fault.

If he has the CH temperature set at high the boiler keeps cutting out
and the fault light comes on. If he turns the CH temperature down to
half it runs OK and does not cut out.

The HW runs OK.

Any pointers as to what might be causing this fault would be much
appreciated.

Failing CH circulating pump? Might not be removing heat from the boiler
fast enough to prevent the boiler tripping out when the boiler is set on
high. That would explain (I think) why the HW is unaffected.

Tim