I’ve got a shower problem: It now only gets proper hot if the heating system is firing, otherwise it’s just tepid. Boiler is one of them Heatrea on-demand whatsits. It has separate “temperature” dials for heating and hot water. The hot water dial is on Max. It was inspected for safety recently and is fine.

Is it a boiler problem or a shower mixer problem?

ta in advance

it’ll probably be the valve/motor for that shunts from hot water to heating. Get a plumber on to see it, you don’t want to go messing with that yourself, easy job for them.
Sometimes there is a manual override, but just call out the plumber/heating engineer.

Does your hot water feed the taps as well? And if so are they hot and do they have a good flow. For a mixing shower (not electric shower) then the flows of cold and hot are critical. If the cold is at a higher flow and pressure than the hot then it may struggle to mix to give a ‘warm’ temperature out of the nozzle.

bath taps: hard to be sure, but I think the hot water in the taps is affected to, but to compensate I reckon I’m running the taps at a slower flow.

I’ll get a plumber to look at the valve/motor for that shunts from hot water to heating

thanks