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

[Milleniumaire]

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).

Thanks.

 

[Milleniumaire]

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!

 

[Dam4n]

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!

 

[Mcalm]

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.