Thanks Tony for you kwik response I did guess that but I was not sure do you think if I do power flash the system it will cure the problem or may I take out the secondry heat exchanger to clean it seperately or take it to adlink and get a reconstructed one.
Have proble with worsecter 28i, It goes to overheat and then lock out two or three times a day after using hot water so we have to push the over heatstat knob on the top of boiler to start working again. any help appreciated.
This is web site www.uk.remeha.com and the guy called Mike Freeman used to work with Vaillant now he is National Specifications Manager-Domestic of Remeha in u.k (o7736827962) and company phone no: is 01189783434
It is a Dutch Boiler, It's been in chelsea show last year and is very new in the U.k. market looks good and powerfull and in compare with the other boiler its cheap that's all I know about it.
I have been asked to look at a Suanier Duval- Thema classic F24E with 3 years old everyrhing is working fine but sometimes hot water get cold.
I checked the domestic heat exchanger it was clean and also the divered valve is working fine I thought the water flow switch ( or water sencer switch)...