Vaillant ecoTEC plus - Hot water goes cold

Hello! I got a problem with my boiler and I would be grateful if someone could let me know what the problem is and what I need to do to fix it. I'll describe the problem below:

- When I turn the tap on the water gets very hot momentarily and then the temperature starts to drop. On the boiler the number usually goes down to 34 and stays there. I have left the water running for a few minute at this point and nothing else happens.

- But if while the water is running I press the reset button on the boiler, then the number drops down to 28 at which point the boiler seems to start running, the "C" starts flashing and the picture of the flame comes on. The water heats and up and the number goes up, but usually stays on 48. The hot water usually works at this point as long as I don't turn the tap off. Very occasionally the water goes cold again.

- Very very occasionally when I turn the water on, the number on the boiler (which is starts off on 60) drops to around 47-48 and the boiler (the flame and the flashing C) turn on at that point and I continue to have hot water.

Not sure if it is relevant, but I have removed a couple of radiators and capped the pipes. I have pressurized the central heating. But I have the central heating switched off.

I would be grateful for any ideas what the problem is.

 

those numbers your looking at is not hot water temp , what does it say when you press i on front of boiler with ch off

edit you have preheat on

 

Really? Strange, it has the Celsius sign next to it.

When I press the button, it says 5.31 (or is it S.31) which drops to 5.21 when I turn the water on, and then climbs back up to 5.24.

 

just re read you need someone competent to have a look for you

 

So does the thermometer I use to monitor my body temperature!

 

Surely C is preheat facility, is it not?

 

it is , agile was being sarcastic i think

 

C=Comfort in Vaillant terminology.

Try running a hot tap and feeling the central heating pipe on the far left, it should not get very hot.

Also check turning the HW temp knob; does it aqdjust the LCD temp display whilst it is being turned?

 

Sorry, I didn't get notified of the new messages. Thanks for replying.

The central heating pipe does get very hot. What does that mean?

The number does change when I turn the nob.



Regarding the other questions, there are two Cs. One at the top right which is the celsius sign. The other other the bottom centre which I presume is the preheat.

 

well it means that the control knob has not snapped and that you need a pro to look at the divereter valve for you

 

Hello - I also have an ecoTec plus 824 and last winter the water kept going cold, would only stay hot if I turned the taps on very slightly. Had an engineer out and he flushed the system - no change, he replaced the heat exchange, no change and then replaced re pump - that worked and the water was fine. Until now. 10 or 11 months on the same thing has started. Engineer is coming again but is there anyone who knows Vaillant well who can point us in the right direction? It can't be the pump again. Last time I left it til I had zero hot water as I was advised to reduce the flow for the winter. While this worked for a while it obviously wasn't the solution. Any advice appreciated - I posted this in my own thread but the only response I've had is get an engineer! Obviously I'm doing that but he's a Baxi man mostly and this is his first Vaillant!

 

You seem to have little faith in the engineer you have chosen.

Vaillants are so common that an engineer who regularly repairs boilers would be very familiar with them indeed.

I suspect he is primarily an installer and not a repairer.

Let him come by all means but don't pay if he is unable to repair it.

Any competent engineer will be familiar with your boiler and will know what to do to fix it.

Tony

 

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