Problem with Viessmann Vitoden 111-W

[ey143]

Got the above 4-year old combi boiler which has a built in 40 litre storage tank.

Had a radiator removed and a new towel radiator fitted by a handyman.
Boiler went on the blink after he partially drained the system to also change some pipe work in a bathroom and capped off each side of the radiator return and flow.
F1 but mainly F2 error msgs appear on the boiler LCD and once or twice an F (d) error msg appears.

I manage to get the central heating working again but the hot water seems to throw up an issue and the temp on the boiler fluctuates between 80-110 degrees but then stops working again after making some noises.

Spoke to Viessmann technical who said that it sounds like air trapped in the boiler system itself, probably heat exchanger related and I’d need a service engineer.
I should add that I’ve bled the system and even emptied it by opening the main rad drain valve and opened all radiators to ensure no trapped air.

Called my admiral home emergency policy who sent someone with what I considered to have broken English. He says he "thinks" the pump is weak. I think he’s talking rubbish. I managed to get the heating working by switching off the hot water in the config settings and it works. I then set the hot water at 30 degrees so we at least get some tepid water and the boiler does not get too hot. Anything higher and we eventually get the F2 errors again.

Any idea what this sounds like?

 

[ey143]

Have now been told its the one of the heat exchangers that is the issue - sludge in the system.

 

[Agile]

I would be very worried if the system water was at 110 C.

I expect that I would want to keep at least 30m away! And find someone to go inside and turn it off!

 

[ey143]

It has safety cut outs preventing it from getting any hotter and the fan throws out excess heat, so it’s fine. But that still needs sorting.
The plate heat exchanger is blocked.

 

[ey143]

I'm having to come back to this same issue again because despite having spent nearly £600 to powerflush my boiler system shortly after my original post in March 2022, I still have problem after spending a more money to get someone to put some MC3 cleaner in my Magnaclean Pro 2 filter.

WHenever I get these F2 error messages and the boiler starts to get to 90 or 100 degrees on the hot water and shut down, I do what last gas engineer did and clean the filter and put more MC3 in there and it starts working again and doesnt overheat but still reaches 80/85 degrees before powering down to 1 heat bar but at least we get hot water.

In 12 months I must have put about 4 bottles in. I know you're supposed to flush it out after 24 hours but I havent and it doesnt seem to have done any damage.

Am I able to open the outside radiator valve whilst opening the filling loop on the boiler and letting the pump run to model a soft power flush and so that the pump flushes out the water to the external tap/valve thing?

 

[Johntheo5]

Could you run with high DHW temperatures of say 55/60C after the power wash a few years ago?

Was the plate heat exchanger replaced?