Vaillant Ecotec - using VR10 on a regular copper tank

[Locoblade]

Hi All

We've just had a 618 Ecotec Plus installed with VR65 and VRT360 controls connecting to a regular copper vented tank.

When installing, our electrician connected up a generic Honeywell tank stat to the VR65 in the usual manner, but whilst browsing some threads on here yesterday, I saw a few mentions (by SimonD, softlad1971 and Agile IIRC) of using the VR10 thermister/VTC supplied with the VR65 instead of the tank stat, which then gives more control by allowing the water temperature to be set from the VRT360 and allowing the one time cylinder boost function work.

To satisfy my own curiosity I did some tests on the VR10 with a multimeter and confirmed that it shows the same resistance when placed against the tank compared to holding the tip directly under running water from the closest hot tap, so it would appear that it can achieve an accurate reading through the copper tank. I then took this a stage futher and used a drill bit (not in a drill!) to cut a small vertical hole in the foam lagging just below the existing stat to house the thermister, so it slides snugly down the side of the tank touching the copper along its entire length, with a little heatsink compound to ensure a good contact.

I then removed the tank stat connection to the VR65 and connected up the VR10 instead, and it does seem to work as expected. If I set a low water temp on the 360 then force a tank recharge (special function 4?), it shows the demand temporarily but doesnt fire the boiler and cancels the request as expected as the tank is already hot enough, and if I set it high it does fire the boiler up and heat the cylinder further.

Ive got a couple of questions though, for those who know the Vaillant boilers well as my installer hasn't had a huge amount of experience with Ecotecs in the past.

Firstly, I've gone back to the tank stat at least temporarily until I can double check that it's OK to run it like this, can anyone confirm?

Playing devil's advocate though, what would happen if the VR10 was pulled out or failed, I guess its the same scenario as the tank stat failing, with overly high water temps? In this scenario does the boiler limit how hot it can get anyway by only providing water at a set temperature?

If I can run it with the VR10, can anyone advise what the water temperature dial on the boiler will do in this situation, and what should it be set to? The manuals don't explain it very well and I didnt get time to check last night, but will the boiler talk to the 360 and have the same setting, will the boiler be over-ridden by the 360 and ignored, or does the boiler need to be set higher than the VRT360 to allow the 360 to retain control?

Also, is there a way I can check the actual water temperature in the tank either on the VRT360 or on the boiler? If I press the + button on the boiler it seems to show a temperature reading thats different to the flow temp shown normally, but the installer/user manuals don't appear to mention what this is, is it the tank water temp or something different?

Many thanks
Chris

 

[simond]

You are best fitting a dry pocket for the thermistor, but it will work OK up against the lagging.

On VRC430 control, both boiler knobs should be on 100%, can't recall whether this is the case on a non WC VRT360. We don't tend to use VR65 now unless we are fitting VRC430, because the VRT360 is a clumsy piece of kit.

If the thermistor is removed the cylinder would not get any warmer than the boiler eg: max 75C.

I would suggest buying a VRC430, it's a much better controller, and you are already 95% of the way there to a weather compensated system.

 

[Locoblade]

Hi Simon

Many thanks for that, I did read about your mention of an essex boss to make a pocket but the thought of cutting the tank put me off!

Regarding controls, my plan was to get a VRC430 and thats what I'll probably do in time anyway, but there were none in the country when we ordered and vaillant didnt seem confident they'll have any before the new year so i got a 360 at least for now so we could get the install done, putting in the VR65 so we could upgrade.

I can see what you mean about the 360, its not quite so bad if you're fairly tech savvy but it still confused me for a bit, as it appeared to only have 3 heat programs in total until i worked out they were all seperate when you select different days, something that isnt clear in the instructions. I certainly couldnt imagine my parents or even my wife being able to fathom it all out and use it intuitively, far too complicated.

Thanks

Chris