Vaillant Ecotec Plus 620 vr10 vr66 DHW issue

[adam_no_understand]

Hello,

Thank you for giving this a read. I have a plumber coming back next week but wondered if anyone had any insight into the issue before then.

I have an
Ecotec Plus 620
Single zone
Unvented hot water cylinder
Using two zone valves and a vr66/2 wiring centre
Vaillant gateway with sensoroom

The cylinder stat has been replaced with a VR10 thermostat. The stat has been installed in the dry pocket and wired into the VR66/2

So the VR66/2 is set to 1 and looks to be wired as the diagram above

So I have the Vaillant gateway and can choose hot water boost which I think is a feature unlocked by the thermostat. The central heating works perfectly. The issue I have is when direct hot water is enabled and on it literally never turns off... I got concerned given my taps were burning hot and it was still 75 flat flow temp without any hot water use. So we have turned dhw off and awaiting the plumber.


My assumption is the VR10 just isn't working hence why it doesn't turn off when up to temperature. Any thoughts welcome.

Kind regards,
Adam

 

[Harry Bloomfield]

Have you checked the resistance of the VR10? It's just a simple thermistor, and its resistance should vary dependent on temperature. Just warming it with your hand, is enough to cause it's resistance to change..

I often find, that when I click on 'boost', that it seems to stay on boost, until manually cancelled. They way I would expect it to work, is once it gets up to temperature, it would self cancel.

 

[adam_no_understand]

Good shout. I haven't but I could give it a go, it says on the packet what it expects and this would atleast rule out the thermostat itself rather than the controls

@Harry Bloomfield do you know if you can check the temperature reading anywhere? I searched all the menus

 

[Harry Bloomfield]

@Harry Bloomfield do you know if you can check the temperature reading anywhere? I searched all the menus

It's a few years now, since I last explored my controls, and it's a different model to yours, but all I could find was an indication of up to temperature, or not up to temperature.

My system is set to 60C cylinder temperature, 75C boiler flow, when heating the cylinder water.

 

[RandomGrinch]

I may be wrong, but I believe the VR10 is a temperature sensor.
You currently have it connected to the stat terminals; these are expecting an on/off signal from the stat, not a continuously varying resistance.
I believe the VR10 should be connected to the NTC terminals...

 

[Harry Bloomfield]

I may be wrong, but I believe the VR10 is a temperature sensor.
You currently have it connected to the stat terminals; these are expecting an on/off signal from the stat, not a continuously varying resistance.
I believe the VR10 should be connected to the NTC terminals...

Correct - Well spotted that man!

I wonder who wired it to the wrong terminals?

 

[adam_no_understand]

Oh I thought this was correct given the text under the wiring diagram, number 38

It mentions to install the thermostat to clamp CYL. I wonder if it's a difference between a VR10 and some of their other fancy thermostats?

 

[Harry Bloomfield]

Oh I thought this was correct given the text under the wiring diagram, number 38

It mentions to install the thermostat to clamp CYL. I wonder if it's a difference between a VR10 and some of their other fancy thermostats?

The instructions are not that clear, it was obvious to me, that the thermistor might need to be connected to different terminals, to the stat., but the instructions didn't make it as obvious as it could be.

 

[Mister Banks]

Oh I thought this was correct given the text under the wiring diagram, number 38

It mentions to install the thermostat to clamp CYL. I wonder if it's a difference between a VR10 and some of their other fancy thermostats?

View attachment 363205

It’s not a thermostat though, it’s a temperature sensor.

 

[RandomGrinch]

It mentions to install the thermostat to clamp CYL. I wonder if it's a difference between a VR10 and some of their other fancy thermostats?

I think it's clear
The VR10 is a temperature sensor and not a stat...

 

[adam_no_understand]

Okay thanks, so this needs wiring to NTC?

 

[Harry Bloomfield]

Okay thanks, so this needs wiring to NTC?

Yes, but I agree, not many people would understand that NTC might mean cylinder temperature sensor.

 

[adam_no_understand]

Thanks guys. Will talk to the plumber, and of course report back even if success to help any later readers

 

[Harry Bloomfield]

Thanks guys. Will talk to the plumber, and of course report back even if success to help any later readers

Can you not swap it over? Only takes a second, and might save cost of the plumber, or did he wire it wrong?

 

[adam_no_understand]

Yes, I have and it's working perfectly! I still have hot water boost, I now see the hot water temperature on the app too

The only issue remaining is the thermostat it replaced on the hot water tank was part of a dual thermostat which also housed the hot water limit which is meant to be wired into the boiler system power... Word of warning that some cylinders have a coupled thermostat and hot water cut off thermostat.


So I need the plumber to come and connect that in series with the fused spur live so that I have a safety mechanism if the thermostat fails and cuts the power. It's also needed for building regs.

So I have a working system but not yet a safe system. Thank you so much for everyone's advice.