VR 10 and VR 11 probes with Vaillant VR 71 Wiring Centre

7 Jan 2010
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United Kingdom
Although I bought a Vaillant VR 71/VRC 700/VR 91/VR 91 pack earlier this year, I've only just got around to opening the boxes to look at the goodies inside, since I'm almost at the point of getting my heating engineer in to do some work on my system.

The VR 71 wiring centre comes with 4 x VR 10 probes and 1 x VR 11 probe. I've had a quick look at the system diagrams that are provided and it appears that the VR 10's are connected along with each valve. My current VR 61 has no such connectors for VR 10 probes, only for the valves.

I believe the VR 10 is a temperature probe, but I'm not sure. I assume the VR 11 is the same! What is the difference between the VR 10 and VR 11?

What is the purpose of these probes? I'm not really seeing a use for them in my existing system that comprises of DHW + UFH zone + CH zone (soon to include a second UFH, hence the upgrade from VR 61 to VR 71, with related controls).

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To answer my own question, it turns out the VR 10 sensors are VERY important and MUST be connected to the VR 71 wiring centre otherwise the system doesn't work. My Vaillant engineer found this out while installing the new VR 71. Initially he didn't use the sensors, then called Vaillant who told him they MUST be connected. The sensors have to be wired up to each zone connection on the VR 71 and the probes attached to the relevant flow pipes for each zone. In my setup, a sensor should also be connected to the new LLH flow, but the engineer didn't do this! The system works without it and I only spotted this when querying Vaillant about how their schematics didn't match my system. Eventually, they supplied me with a schematic which was very similar and this allowed me to confirm exactly how it has been setup by the heating engineer. There were a few settings on the VRC700 controller that weren't correct also! To quote my installer "Vaillant have made this system far too complicated"!

Obviously these sensors are being used to measure flow temperatures for each zone, however, I'm unsure exactly what impact this has on the way the system works.

In the early days I struggled to get the house to warm up and reach the desired 21 degrees C set on the VRC700. After lots of experimentation and questions to Vaillant it now appears to be working okay, although I'm now having to use a higher heat curve than when the old VRC 430 was used and prior to the LLH. I also worry about the lack of condensing as the temperatures of the flow return between boiler and LLH (primary circuit?) are always very high and very close together!
Hi. A bit late but had the vr71 installed yesterday with same problems. Probes not attached to anything so flow temps been crazy high. Struggling to speak to anyone who can help as installer not 100% on it either!
I hate to say this, but the problem with a large majority of heating engineers is they lack the understanding of how to correctly wireup and configure the new generation of computer controlled e-bus Vaillant control systems to get the best comfort and efficiency for the end users. And most will tell you that Vaillant systems are complicated - but in reality they are very simple.

Flow/Return temperatures should ideally be around 20C to achieve the highest efficiencies from a condensing boiler. The VR10 sensors are used to constantly monitor and modulate the gas flow rate and with multi-zone systems with additional Thermostats for each zone requires a sensor. For UFH systems, which operate at lower temps compared to the radiator zones, again a sensor is required to monitor that circuit and not to mention. Additionally, the VRC700 system used Weather Compensation for which a special VR11 is used to monitor the outside temperature to modulate the boiler to maintain a constant temperature. It also has the capability of monitoring the storage temperature of the DHW cylinder. Especially useful if one has PDHW enabled to provide on demand hot water 24/7.

The majority of the Tech's only know how to wire heatings systems with a standard ON/OFF wall thermostats.

Anyone who has invested in the VRC700 range of controls, before engaging their heating engineers it is important that they clarify with their heating engineers if they have the experience of wiring these new range of wiring centres/sensors and programming the controls correctly.

I strongly advise to look for an engineer who has done the heatgeek courses. https://www.heatgeek.com/find-a-heat-geek/

Just my two cents from an ex-vaillant engineer.
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Awaking this old thread... I've got an Ecotec Plus system boiler with conventional hot water cylinder, and it's always irked me that I indeed have the simplest form of control, with programmer and room stat. So not only is there no weather compensation, but the boiler isn't even aware of whether it's supplying heating or hot water, and therefore can't drop the flow temperature for heating. With all this mantra about flow temperatures (easy on a combi) I'm looking at this again.

One thing that continues to puzzle me, and maybe Mcalm knows the answer, is why they insist that you have to use their hot water cylinder. What's to stop you putitng the VR 10 sensor on your existing hot water cylinder? Quite apart from the expense and upheaval of replacing a perfectly good high recovery cylinder, my mains water supply flow rate is not great so I much prefer a gravity-fed hot water system.

It's worth repeating that Vaillant do themselves no favours at all by not as far as I know publishing a table of what is compatible with what amongst their large range of modules. But that does align with their customer-hostile practice of using proprietary communications protocols (and consequently suffering the indignity of having to make an OpenTherm converter for The Netherlands where such protectionism is banned). I assume they think it's not in their interest to help their customers in this way because it would facilitate re-use (NB with a consequential environmental benefit) and hence harm their sales.
Hi Crosseyed,

You do not need to use a vaillant cylinder, not sure where you got that idea from! :) Obviously Vai;lant will illustrate use of their own product in marketing

The vaillant VR10 probes fit beautifully into any 6mm (general standard size domestic) thermopocket such as megaflo or similar.
If you are using a traditional open vent copper/stainless cylinder (where you are unlikely to have a thermowell) the VR 10 can be inserted in between the polyurethane lagging and the cylinder wall. Cut a small square out of lagging at bottom third/quarter of your cylinder poke VR10 into place against cylinder and replace the lagging square.

You are right that the documentation of the Ebus controls is (and always has been) diabolical (in fact all their documentation is poor). However the controls are enormously flexible and capable controls that put many commercial systems in the shade for very little money (relatively). Unfortunately the vast majority of UK installers are too stuck in their ways to learn anything new and dismiss Ebus as too complicated :( Its really not complicated at all, it's just not a Sundial Plan!

Just to clarify an earlier error on this thread: the VR10 (grey cable) is the standard temp sensor for domestic heating and hot water, it is used throughout the Ebus control range. The one exception is the VR11(black cable) wide range,high temp sensor which is used exclusively as a solar thermal panel sensor (yes - the ebus controls will integrate control of your panels and multiple solar loads! pools, cylinders, thermal stores etc)
The outdoor sensor is a (VRC693) is ready housed in a small grey plastic housing for wall mount and cannot be confused with the VR10/11
There is another outdoor sensor (VRC9535) but it is not sold in the UK as it integrates a time signal antenna for a signal not broadcast here in UK

To address your initial point: If you need to access the twin boiler stats in an ecotec plus boiler and don't want to use ebus controls this is readily done by using the RT or 345 switched live terminals( terminal designation dependant on boiler age) and then the C1C2 plug on the boiler wiring loom to provide volt free demand for DHW via a regular cylinder stat and zone valve (valve orange and grey wires Straight to C1C2) you can even buy a plug and lead for the C1C2 connector if you want though I normally cut plug off loom and use chocbloc/crimps/barrier strip cos I'm cheap ;)
This will give you priority hot water with boiler flow temps set differently for DHW demand than a space heating demand.
If you want to keep heat demand ELV then newer boilers have a 24V space heat demand available.

As regards opentherm - as you say Vaillant make the VR33 opentherm adaptor which can be easily purchased online from the NL - many Honeywell Evohome users use the Evohome OT controller and VR33 to good effect. There's much debate on the Home Automation forum if you're interested.

Ebus far far pre-dates the arrival of OT and is streets ahead in capability and flexibility, can be configured to control tens of mixed circuits, multiple cylinders/stores, solar thermal, up to eight heat sources in cascade (gas boilers or heat pumps) and integrates with app control and the post install zoning Ambisense rad trv body sensor/motors (akin to Wiser/Evohome) and all the usual crop of digital assistants.

OT is essentially a peer to peer system (though certain commercial controllers like HW SDC Smile and Remeha/Broag etc do extend it) and its only really Honeywell (An OT member) that have made any real effort to market domestic OT stats here in the UK Also despite it being a supposedly 'open source' standard many controllers run into problems with incompatability with temperature protection/anti cycling limits in connected boilers that prevent the OT demands being satisfied (Ideal (who did produce some native OT boilers) have a particular issue with HW controllers) AFAIK OT really hasn't gained traction here, probably for similar reasons to Ebus and what OT native equipment that was on the market a few years ago is disappearing.

If you want any help sorting out best options for your system PM me

Simon (30 years an Ebus installer!)
Thank you!

I inferred you can only use their own cylinders from everything I have read that Vaillant publishes, which is not just marketing material, and scouring this and other forums for experiences to the contrary. If they want to make clear that any cylinder can be used they could still illustrate with their product but simply acknowledge that fact somewhere. You could accuse me of being over-cautious but it would be more than irritating if I bought some expensive controls and found I couldn't use them.

I am happy to accept your explanation that OpenTherm has limitations which would impact on the functionality of Vaillant controls. However, that is not really the issue - the issue is that Vaillant uses prorietary protocols on top of the documented eBus spec which they keep secret. Having to spend more than £100 on an imported OpenTherm interface which Vaillant clearly does not want you to use in the UK is not a great solution.

One thing that irks me about Vaillant controls is that they don't have a simple boost button for central heating, to make it come on for an hour or two hours, like my old Horstmann programmer - possibly because they base their methodology on super-insulated homes with underfloor heating which take a long time to react so best leave the heating on all day throughout the dwelling to achieve a constant internal temperature. My house and lifestyle do not align well with those ideals.

Your suggestion that you can use conventional controls to tell the boiler whether whether central heating or hot water are being demanded is an interesting one, especially as I could retain that boost facility, but I'm guessing I wouldn't get the same efficiency gains as weather compensating controls. It's a long time since I looked at the boiler PCB and I remember seeing the string of resistors connecting to the terminal which activates operation; I don't remember seeing more than one, which would allow it to have two inputs, but then I wasn't looking for it.

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