Worcester 28i boiler switches off when using shower

[emoghal]

I have a Worcester Greenstar 28i Condensing boiler which works absolutely fine when using the central heating or when ideal, but recently it seems to switch off after about 10 minutes when someone uses the mixer shower.

I don't have any power shower and am using the mixer tap shower, has anyone got any idea what could be causing the boiler to switch off. It works fine after I reset it.

Any suggestions would be most welcome...

 

[cjb1971]

If youve got the temp of the dhw turned rite up to the max and the shower isnt drawing off a great deal of hw it might be tripping out on the overheat stat -or the over heat stat could just be faulty.

 

[gas4you]

Is sussex a hard water area? If so I would suspect the dhw plate heat exchanger is scaled or partially blocked.

Has the flow reduced noticeably through the hot taps?