Worcester Bosch 240 rsf trips off

[tk direct]

I have a Worcester Bosch 240 rsf that after filling a bath about an eighth full with warm/hot not boiling hot water it trips off and i have to press the red button to reset it. The central heating side works fine and the water pressure seems ok.
I have checked this forum for suggestions and tried as suggested the diaphram but it is going in and out and switch the switch.
I have no more ideas so can one of you help me please.

Thanks

 

[ChrisR]

What's the hot flow rate at the bath tap?

It's probably scale either reducing the flow or reducing the heat-transfer in the HW heat exchanger. Either way the boiler should be able to cope, by turning the flames on and off to give the right amount of energy on average. It appears to be overheating instead, so it looks like 2 problems.

Descaling can certainly be done, someone like COG will know more about the other prob!

 

[fitz1]

Common problem . Domestic hot water heat exchanger needs cleaning out.If not successful,new one approx- 170 quid plus fitting.

 

[ChrisR]

BUt should the boiler not just turn the flames off rather than overheat?

 

[tk direct]

Thanks guy's for you help.
I got fed up working on it and got close to calling somebody out when i thought stuff it i'll buy another pump and see if this helps it and bingo had a bath with the wife and yes it was very hot and the water was aswell.
But i still do not understand why the pump caused this problem as the pump only works for the central heating side don't it ?

Thanks

 

[COG]

If the hot eater temp is less than 30deg C above the cold at 9lt per min and the body of the heat exchanger is upto 80 then you have a blocked or scaled up water to water heat exchanger.All the normal poor circ problems can take place such as slow pump or blocked diverter valve and scaled/sludged up gas to water heat ex,faulty thermisters dont usually lead to overheating to the amount you say.Worcester would fit a new heat ex for around £230 they can be cleaned out if you can find someone to do it properly.

 

[tk direct]

Cheers Cog