Vaillant ecomax 828/2e hot water problem

[Drl589]

My boiler is being tempremental over the past couple of months.
The CH side works fine. The DHW however doesnt.

When i turn the hot tap on the boiler ignites and displays the relevant codes
S14 - Burner ignited (heating operation)
The set point on the dial is set at 62 degrees. It fires up and goes past this to around 70, however it keeps rising until it reaches about 85. Once it hits about that temperature the status code changes to
S53 - Delay mode due to lack of water in system (~20 mins.)

Does anybody know what could be wrong.
I had a boiler engineer out who took the heat exchanger off and cleaned it in something. And have also changed the small filter that goes between the heat exchangers but to no avail.

Ive heard various things, some say it might he the pump, although i cant see it myself if the central heating works fine?
And some have mentioned an NTC sensor of which there are two i can see on the exploded drawing.

Any help would be appreciated

Dave

 

[Drl589]

Forgot to mention i also replaced the rubber hose last year so that should still be clear?

 

[Hason]

Difficult to fully clean plate heat exchanges, if heating fine either divertor not moving over fully or plate blocked, had the same for a customer last year thought I clean plate out but since I changed it all sorted
Good luck

 

[Agile]

Using the right chemicals I would say that it IS possible to properly clean any plate HE.

But I use two different acids.

Some think that just shaking them out does the trick.

Well it does get some loose dirt out but does not clean them properly.

Tony