Vaillant 828e hot water problem

[terryca]

Hi, this is my first post here.
I have a Vaillant 828e combination boiler that is 8 years old. When the central heating has been on for a while, it will not deliver hot water to the taps. The green light flashes and the orange comes on as normal. I have taken the cover off when this is happening, and can see that the burners are on constantly. The case gets very hot and the radiator nearest the boiler gets warmer. To get hot water I have to turn off the central heating and turn the boiler off and on a few times.
Two central heating engineers have looked at it but they did not see the problem themselves. The suggestions from them were to replace the heat exchanger and to fit a magnetic thing to stop scaling.
Thanks for any advice
Terry

 

[bobw1956]

Sounds like the diverter valve is sticking,common on this boiler

 

[Agile]

I am always interested in these things!

On what charging basis did each of these two engineers come?

From what you say we can easily say what the problem is likely to be. Why could neither of the engineers?

Its so common that I always carry a new one with me everywhere I drive to!

Tony Glazier

 

[terryca]

Tony:
One was free, the other charged £20.

I looked at the diagnostics after posting, and the reading (f35) was correct for CH (0) and DHW (1), so that leaves me thinking it isn't the diverter valve.
So - any takers on what is going on?
Terry

 

[Rob]

I looked at the diagnostics after posting, and the reading (f35) was correct for CH (0) and DHW (1), so that leaves me thinking it isn't the diverter valve.

What on earth are you talking about.

 

[terryca]

Rob,
This boiler has a diagnostic display whereby you can push a few buttons and interrogate the boiler.
I misremembered the display code, it is d.35 for the diverter valve.
Terry

 

[Rob]

Yes I understand that. However if the boiler says the diverter is in HW mode yet the radiators are heating up instead why does that make you think the diverter valve is ok?

 

[terryca]

Rob,
Because the diagnostics say so.
The point is - I might think that the diverter is working properly based on that, but I want to know what an expert thinks.
I thought the additional information might help.
Terry

 

[Rob]

Ok so what do the diagnostics say the problem is?

Ill answer for you. Nothing as they can't even see a problem. So why do you trust it so much?

And an "expert" has told you the likely problem in the first post.

 

[Dan Robinson]

Rob, the boiler is there, Agile is not. Of course a piece of simple logic software is going to correct...why would they bother to build a boiler with it otherwise?

 

[terryca]

Rob,
You have no idea how much I trust the diagnostics (if at all). I don't know how the status of the diverter valve is detected or what is detected, so I haven't a clue what the diagnostics is telling me. I was hoping for a considered answer that would explain what is going on, instead I got you.
I am posting here because two separate central heating engineers have failed to diagnose the problem, and I want to find out what people who know what they are talking about think might be going wrong.
For what its worth I too, in my naivety, thought the diverter valve sticking was the issue, but I am worried that two experienced professionals didn't.
Thanks for your time.
Terry

 

[Bunnyman]

Well that's a wrong way to get help mate being rude when he's trying to guide you! If the blokes couldn't diagnose this u need to look for a specialist Combi engineer not a general plumber, just use a bit of ur own logic mate
1. U are running the hot water tap.
2. The diagnostics tell u the divertor is in hot water mode.
3. The radiators are getting hot!
4. What do u think?

 

[terryca]

Bunnyman,
I think its the diverter valve, but I only have a very sketchy idea of how these things work, so I don't know.
.