Vaillant e-bus controls for system boiler simple system

[rjn21]

I am renewing my CH and DHW entirely with (amongst other bits):
Vaillant Ecofit-pure 630, system boiler
Vaillant Sensocomfort 720F wireless controller/room thermostat
Vented, indirect HW cylinder

There is currently only 1 CH zone, being the whole house (although each rad will then have a smart TRV, but that's not relevant to my questions).

The cylinder will need a temperature sensor to feed back to the 720F receiver, allowing it to work out when to fire the boiler to satisfy the set temperature of the DHW.

Will a wired VR10 temperature sensor be ok, attached on the cylinder to provide temperature data to the 720F's receiver / wiring centre?

If I'm just using DHW and/or CH with no zones, is a wiring centre VR66(2) also needed?

Vaillant tech wouldn't speak to me as I'm not an "installer" and my actual installer (whilst brilliant) is a bit unsure as their preferred electrician normally deals with anything like that and they're away at the moment, and I want to nail down the required parts list ASAP.

Thanks in advance.

 

[Harry Bloomfield]

Vaillant tech wouldn't speak to me as I'm not an "installer" and my actual installer (whilst brilliant) is a bit unsure as their preferred electrician normally deals with anything like that and they're away at the moment, and I want to nail down the required parts list ASAP.

That's odd, they speak to me on the phone and respond to emails (usually), although I am not an installer. Trouble is, they are not very technically knowledgeable. Tech email is - RochesterTechnical <[email protected]>

 

[rjn21]

To answer my own questions to aid future readers:

A VR10 NTC temperature probe is correct and connects to the VR66/2 to measure tank temp. If the cylinder doesn’t have a preformed temp sensor pocket, cut a patch of insulation, stick the sensor to the tank with thermal paste, stick the insulation back over the sensor and affix with some tape. The wiring box does have the (less efficient) ability to use an on/off tank thermostat but that defeats the point of the precise control that can be achieved with the 720F and eBUS.

The 720F receiver supposedly integrates into the boiler underneath and connects directly to the boiler by eBUS. There is no dedicated power + eBUS connection port, or hangers, on an Ecofit pure 630 so I mounted the receiver externally, gave it 240V, then daisy chained the eBUS to the vr66/2 then on to the boiler.

If you have a system boiler, with just 1 flow and 1 return, a VR 66/2 is correct and is needed to operate the 2 2 zone valves (S plan) or 1 3 position valve (Y plan). The Vaillant supply chain has both VR66 and VR66/2 in it, both have the same Vaillant part number, but I was told only the /2 works with 720(F) controls. I had to purchase several “VR66s” until I finally got a /2 as no retailer, that I could find, specified /2 or not and they’re all the same Vaillant part number.

There is an error in the wiring diagrams supplied with the 720 (and others) for a system boiler, 1 heat zone and 1 cylinder. The wiring diagram says use basic system code 2 - that’s not correct - with a vr66/2 you need to use system code 1 on the 720 and position 1 on the vR66/2’s rotary selector switch.

It’s hot water priority, which I did know, but then confused myself when the 720 called for heat on the radiators and nothing happened with the heating valve. The cylinder had cooled a bit when the power was off for wiring, so was warming but in priority to the heating, so of course the heating valve wouldn’t be energised. After working that out, all is well.

 

[Harry Bloomfield]

It’s hot water priority, which I did know, but then confused myself when the 720 called for heat on the radiators and nothing happened with the heating valve. The cylinder had cooled a bit when the power was off for wiring, so was warming but in priority to the heating, so of course the heating valve wouldn’t be energised. After working that out, all is well.

That is correct and the reason you cannot supply both CH & HW is that the boiler itself now knows which demand it is servicing and now you can set separate flow temperatures for each mode. I have mine set to max temperature for HW flow, 60 cylinder and I think 60 for CH, but the system actually optimises that latter, for best condensing efficiency. On standard controls, you only see one flow temperature setting. HW flow temperature, has to be set higher than the cylinder temperature, otherwise the boiler would never be able to satisfy the demand.

I set my CH to come on first, then an hour later it does the HW, that way the house is remains warm, whilst it spends the 20 minutes so so heating the water back up - we don't even miss it for those minutes.

 

[Seliaks]

If you have a system boiler, with just 1 flow and 1 return, a VR 66/2 is correct and is needed to operate the 2 2 zone valves (S plan) or 1 3 position valve (Y plan). The Vaillant supply chain has both VR66 and VR66/2 in it, both have the same Vaillant part number, but I was told only the /2 works with 720(F) controls. I had to purchase several “VR66s” until I finally got a /2 as no retailer, that I could find, specified /2 or not and they’re all the same Vaillant part number.

There is an error in the wiring diagrams supplied with the 720 (and others) for a system boiler, 1 heat zone and 1 cylinder. The wiring diagram says use basic system code 2 - that’s not correct - with a vr66/2 you need to use system code 1 on the 720 and position 1 on the vR66/2’s rotary selector switch.

@rjn21 and @ScottishGasMan may also be able to advise

I have a similar single zone system that I have just upgraded to Sensocomfort wireless. My previous controls used a VR66 (but not the /2 version) which I have retained for the moment. I have got everything set up and the system appears to be working ok, way better than the vSmart that it replaced, however I am not convinced that the Room Temp Expanded setting is actually having any Load Compensation effect (it is turning the heating on and off as needed though) - it's hard to know currently as the weather has been so mild the temperature drop overnight has only been about 0.5C below the set point, so not much scope for Load Compensation on top of the Weather Comp.

In your set up, in the Installation Configuration menu, do you have a menu item for Zone 1 in which you have set it to Active and have assigned the Control to it? In my installation config menu I do not see a Zone 1 option, so I'm unable to assign the Control to the zone. I have tried factory resetting the control a couple of times but end up in the same situation each time. If you do have the Zone 1 menu, then I guess I need to buy a VR66/2 in order to get the system working properly. I have found one online at a reasonable price - the VR71 is horrifically expensive.

I already have the VR66 set to setting 1, monozone mode.

I have also emailed vaillant technical for advice but not sure when they are likely to reply.

Thanks

 

[Johntheo5]

Does the vSmart actually measure the outside temperature or is it getting it from your nearest weather station and does it also use the roomstat set temp/actual room temperature in calculating the target flow temperature, if this is how it works?.

 

[Seliaks]

vSmart gets its outside temp from the internet - I found it was usually within a couple of degrees of what Google weather was saying. I don't think the outside temp was the problem with my issues with vSmart - it's what it does with the data to decide what flow temps to request that is the problem - crazy high flow temps on warm days, overshoots, inability to hold a steady room temp. Sensocomfort is proving much more reliable so far.

 

[Seliaks]

Does the vSmart actually measure the outside temperature or is it getting it from your nearest weather station and does it also use the roomstat set temp/actual room temperature in calculating the target flow temperature, if this is how it works?.

The info I could find online suggests that it does use the room temp as well as the internet weather data, but I did a test on a very cold day where I put the roomstat outside, so it was reading about 2C, and with the parameters set to hysteresis it seemed to make very little difference to the flow temps requested from the boiler - maybe 1-3 degrees higher. Whilst if it was on advanced algorithm it seemed to want very high flow temps most of the time unless the room temp had dropped to within perhaps 0.1-0.2C of the roomstat setting from exceeding it. My vSmart unit may have been faulty in some way though.

Here's a link to the technical guide I found online some time ago - it's a bit old, but I doubt the basics of how it is supposed to work have changed.

https://thermogas.gr/wp-content/uploads/2021/10/vSMART_Technical_Guide_EN.pdf

 

[Johntheo5]

It uses the default WC curve for the first two weeks, it would be interesting if someone who is experiencing the problems you got if they commissioned it again and see what's happening during this period.
"Two weeks after the commissioning and thanks to eBus communication, vSMART is able to ask the boiler when and at which temperature to start to reach the right set point at the right time."

You said above, "with the parameters set to hysteresis it seemed to make very little difference to the flow temps" what does this mean?, is that just using the basic WC curve?

 

[Seliaks]

I did completely result my vSmart a couple of times, but it always went out of control quite quickly.

That thing about vSmart asking the boiler when at at what temp to fire boiler to reach the room temp at the required time is also rubbish in practice - most people turn off the predictive heat function as it also plays up and does weird things.

In hysteresis mode, months/years after the first two weeks, vSmart seemed to just follow the WC curve and didn't add much if anything to the flow temps by way of load compensation if the room temp was cold compared to the set point - it just seemed to add a degree or at most two for each degree of difference below set point, so on very cold days when the room temp had dropped overnight it would take a very long time to reach the set point, but at least it didn't significantly overshoot it. Using the advanced algorithm vSmart seemed to add an element of load comp to the WC, but the maths looked very wrong - why should it be asking the boiler for 75C flow temp for a set point of 18.5C and a room temp of 18C, when using a heat curve of 1.6 at an outside temp of 10C?

In contrast, the Sensocomfort this evening was asking for a flow temp of 51C for a set point of 20C and room temp of 19.5C with a heat curve of 2.3 at 10C outside temp, which ties in with Vaillant's heat curve graph.

 

[Seliaks]

@rjn21 and @ScottishGasMan may also be able to advise

I have a similar single zone system that I have just upgraded to Sensocomfort wireless. My previous controls used a VR66 (but not the /2 version) which I have retained for the moment. I have got everything set up and the system appears to be working ok, way better than the vSmart that it replaced, however I am not convinced that the Room Temp Expanded setting is actually having any Load Compensation effect (it is turning the heating on and off as needed though) - it's hard to know currently as the weather has been so mild the temperature drop overnight has only been about 0.5C below the set point, so not much scope for Load Compensation on top of the Weather Comp.

In your set up, in the Installation Configuration menu, do you have a menu item for Zone 1 in which you have set it to Active and have assigned the Control to it? In my installation config menu I do not see a Zone 1 option, so I'm unable to assign the Control to the zone. I have tried factory resetting the control a couple of times but end up in the same situation each time. If you do have the Zone 1 menu, then I guess I need to buy a VR66/2 in order to get the system working properly. I have found one online at a reasonable price - the VR71 is horrifically expensive.

I already have the VR66 set to setting 1, monozone mode.

I have also emailed vaillant technical for advice but not sure when they are likely to reply.

Thanks

Ok, I think I have ascertained that my set up of Ecotec Plus 624 System boiler with a non-Vaillant unvented cylinder with vr10 ntc sensor in the pocket plus Sensocomfort and a VR66 wiring box in a single zone setup is working fine and that the expanded room temp setting is working properly.

After setting the control to a set point of 20C at a room temp of 19.5C and seeing at the boiler a requested flow temp target of 50C at outside temp of 10C and heat curve 2.3, I put the control thermostat outside and saw that after a while it said the room temp was 16C and was then asking for a flow temp of 62C I think, so the Room Temp setting is definitely working, as is Expanded, as the controller does turn off the heat demand once the room comes to temp.

So it appears that if you have a simple single zone setup with a system boiler and cylinder, you don't have to use a vr66/2 wiring box, the older vr66 box seems to work fine. You don't get the Zone 1 option in the installation config menu with this set up, but then again, it's obvious that the control is in Zone 1, as there's no other zones present, and the Sensocomfort appears to recognise this.

I haven't had it set up long enough to know if the Adaptive Heat Curve setting works properly with this setting though. I will keep an eye on the HC setting over the next week or so and see if it gets adjusted.

 

[Johntheo5]

Of course setting the basic heat curves "correctly" to suit ones house has a huge impact on heat up time etc.
Comparing the 2.3/1.6 curves, the 2.3 curve at ~ 50C with a OT of 10C will emit ~ 44.3% of a T50 rad, the 1.6 curve at ~ 42C, with a OT 10C will emit ~ 30% of a T50 rad so the 2.3 curve setting will result in a very hefty, almost 48% greater output, so the adaptive heat curve should help?.