combi boiler high heat trip when running bath.

I have a combi boiler which i am still getting used to. i think it is a BAXI 133HE PLUS COMBI like this one

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trouble is. Every time i run a bath it trips out and i have to wait about 15 mins before it can be reset. I can't remember the fault read out but it is something to do with high / excess heat.

I am pretty sure the problem occurs when the hot tap is turned off thus causing a backlog of hot water that causes some high temp trip. The fact that it is a condensing boiler probably also doesn't help in the formation of hot spots.

The trip doesnt occur when using the shower, filling the sink for washing up or washine machine or dishwasher.

The prolonged and high use of the hot water when running a bath must build up lots of heat in the boiler tubes which has no where to go when the water demand is shut off. I have tried turning the hot water off very gradually but this doesnt seem to help.

I was thinking the problem could be avoided by setting the water temp preset either low or high, but neither worked so i guess there must be some sort of middle setting which will solve the problem.

Any ideas?

Also for maximum efficiency do i set the central heating output temp high or low? there is no thermostat in the house but the radiators have individual valuve controls for manual adjustment so i can set the appropriate temperature no matter the boiler output temp.