Vaillant Ecotec 937+ problem

[Alansmithers]

Hi all,

Hoping someone can help...
We have a 937plus about 8 years old.
Some weeks ago we noticed radiators were hot but no hot water when demanded. Quick fix was to switch boiler off the back on.
Our regular heating guy has diagnosed faulty diverter valve which seems logical to my very uneducated mind!
However, today we've had radiators on permanently even though: thermostat is set way below ambient temp, controller is in the OFF setting and the storage tanks have been turned off (temp dial on boiler all the way to left so the 'C' symbol is off - we did that a few weeks back so as to prevent any demand for storage tank heating). The diverter valve is due to be replaced in a couple of weeks.
Can anyone tell me what could cause the boiler to fire when there is no demand from hot water, room thermostat or pre- charge tanks?
I'm now worried it might be more than a duff valve!
Thanks in advance
Alan

Quick update on this. According to the display, demand is coming from heating - S1, S2, S3, S4. The controller is set at Always Off and the room stat is set very low - well below actual room temp.

 

[Chalked]

Why not let the guy who diagnosed the fault fix it?
Will be the diverter, and could be other issues. But that’s part and parcel of repairing boilers.

 

[Alansmithers]

Why not let the guy who diagnosed the fault fix it?
Will be the diverter, and could be other issues. But that’s part and parcel of repairing boilers.

We've got every intention of letting the guy who diagnosed the fault fix it. Just that there have been further symptoms since his visit and I was wondering if anyone in here might have come across the same set of problems and might therefore be able to help out with any more diagnosis if required.
Also, TBH, I'm really curious to understand how a faulty diverter could cause a demand for CH when both stat and controller are off.
To be clear, I have complete confidence in our heating engineer.
Thanks for your comments though

 

[Riley]

I’m glad you do have faith in them. Keep it that way. We will not provide any information relating to the repair of boilers to non gas safe engineers. I really really really really really wish that people didn’t feel this constant need to “just try and find out the issue” but of course they have no intention of repairing it them self rolleyes seriously, just have faith in the person you’re paying to use their training to sort you out. Most engineers will be hacked off if they turn up and you say that you’ve done some research and the fault is...... leave it to the pros

 

[Alansmithers]

Well thank you for your helpful reply!
Is it not just possible that I might simply be interested to know what the fault is and what the logic is?
The engineer we use is always happy to discuss what he's doing and why. He knows that I'm curious about how things work but he also knows that I don't mess around with gas boilers.
Have a nice day

 

[Alansmithers]

I’m glad you do have faith in them. Keep it that way. We will not provide any information relating to the repair of boilers to non gas safe engineers. I really really really really really wish that people didn’t feel this constant need to “just try and find out the issue” but of course they have no intention of repairing it them self rolleyes seriously, just have faith in the person you’re paying to use their training to sort you out. Most engineers will be hacked off if they turn up and you say that you’ve done some research and the fault is.... leave it to the pros

 

[Alansmithers]

I would have thought that in order for the boiler to fire for CH, at least two conditions must be true - demand from the room thermostat and heating controller at 'ON'. But, like I said at the start, I'm uneducated in these matters. I have absolutely no intention of 'having a go myself' but I would be interested to know what's wrong with my logic above!
I'm sure there must be someone who's not afraid to educate me. Anyone?

 

[Riley]

Your logic high level is right and my reply seemed more angry than intended because the emojis went potty. Apologies for that. The fact is though that you will not get answers on here. Understanding logic or not. You must look at it from our perspective you may not have a go but your thread is in an open forum the next have a go hero might

 

[Riley]

Well thank you for your helpful reply!
Is it not just possible that I might simply be interested to know what the fault is and what the logic is?
The engineer we use is always happy to discuss what he's doing and why. He knows that I'm curious about how things work but he also knows that I don't mess around with gas boilers.
Have a nice day

I also have no problem explaining to customers what the problem is but I will never discuss parts