quote=theresa1;959217] Surely the heat exchanger is well able to stand the temperatures at two thirds of the setting?[/quote]
Maybe, maybe not, without the correct wiring the boiler cannot function 100% the way it has been designed, there will be a overheat limit switch on the boiler that will protect the boiler to a certain extent from overheating, most boilers i come a cross are wired the same as yours and are left alone (which doesn't make it right)the boilers are only rewired when the over heating becomes a problem, so i wouldn't blow this out of proportion, the way your boiler is wired is wrong and i wouldn't be happy with it in my house, but if you leave the stat down the effects on the boiler is reduced, but as a proper gasman i would have to advise the fault is rectified, Gary.