Vaillant turbomax plus 828 flame on flame off

[bassmonster]

Hi all, we went to a boiler where both central heating and dhw would turn on then off again. We then cleaned the plate heat exchanger thinking it would solve the problem but there was no change.

We then opened the combustion chamber. Please see attached pic. I take it the black marks and the green around it is as a result of a leak? We couldn't actually see any leaks it self though.

Would changing the heat exchanger fix the problem or is there something else we should be looking at too?

 

[AWheating]

Is there any circulation out of the boiler? Hex needs changing.

 

[bassmonster]

yes, circulation is fine as we installed a magnaclean and within 10 minutes, it had about 2mm of sludge...their system needs a thorough clean but customer not wanting it done due to finance.

The hex will be changed but i just have this feeling that's it's not going to fix the problem. can a blockage in the hex cause the flame to cycle through on and off?

 

[AWheating]

If the heat is not being removed from the boiler then it will cycle. Scaled up or blocked hex may cause thiis

 

[bassmonster]

thank you, much appreciated...