Multi-zone S-plan setup using Vaillant eBus...
Hi all!
I am successfully running an S-plan set up using 'basic' 230V relay switching, and am really struggling to see if/how I can utilise the (more efficient) eBUS. I've tried Tado help and searching the forum but am a bit lost - can any experienced users help me?
Current setup (all working nicely with 'basic' 230V relay switching)::
- Vaillant 637 system boiler (unvented)
- S-plan piping to 3 heating zones (ground floor, 1st floor, top floor) and a fourth HW (heating a vaillant unistor cylinder)
- I have three V3+ Tado zone controllers located on different floors:
- Tado wired thermostat for ground floor CH
- Tado wireless receiver (and temp sensor) for first floor CH + HW
- Tado wired thermostat for top floor CH
- Each zone has multiple Tado TRVs, able to call the corresponding CH zone controller and fire the boiler accordingly (it works perfectly all bar not using eBUS).
I want to use eBus (as boiler doesn't support OpenTherm) to get the benefits of modulation. I'm happy to re-wire and/or fit different Tado devices, but I'm not clear how to set this up, perhaps my first questions are:
- I presume the wired thermostats support eBus (using the wired DC -/+ connections)
- Can I run multiple eBus's into one, or do I need a device between them (eg Vaillant VR65 / VR65)
- will the Vaillant VR65/ VR66 support 3 zones + HW?
- Can I use an EU wireless receiver (with eBUS) for HW (I have one to hand)?
- Will this also run the ground CH zone, or do I need a third wireless thermostat in this instance (I have one to hand)
Any experience appreciated! Many thanks!
Comments
-
@acull2000 Hello. Looking at your Vaillant 637 boiler spec:
the boiler appears to modulate internally from 7.1kW to 40.5kW (condensing) in relay mode. The question in my mind is how much more efficient could/would it be in 'bus' mode?
@policywonk can you comment/advise on the 'bus' questions?
FYI. Our Baxi boiler modulates internally from 7 kW to 28kW. From February 2022, these are the results in relay mode, while actively managing the Room schedules to suit our diaries.
0 -
Hi @acull2000. You've really done your homework- and @wateroakley is strong on documentation of outcomes. So - a good start.
It is true that that boiler's version of eBUS is well within the capacity of the V3 series to handle. Vaillant's VR65 is the device that most users here seem to have chosen to create a wiring centre that administers an S Plan.
- In the last year there was a surge of end users trying this and, whilst they all had a drama about making sure that the menu control at the boiler panel was correctly set, they seemed to get it to work.
- You will need to ensure that you have a Vaillant eBus compatible thermal sensor for your Vaillant Unistor. IIRC - please check with Vaillant - it comes with an option to be handled in eBUS mode in its installation kit- and that sensor must have the capacity to use the VR65 to trigger the motorised valve for HW.
- One hurdle is finding a VR65/VR66 with a dealer in stock - and a Vaillant experienced installer to fit it, and interface it correctly to your zone valves. From the guides it seems that the VR65 will only handle one CH zone, whereas the VR66 will handle at least two.
- Another is to clarify from Tado and Vaillant that if the VR66 is to be used, that it handles communication in eBUS version 1 mode, not eBUS version 2 onwards. The V3+ series only handles eBUS version 1. The second, much later eBUS version has protocols which Tado did not find a way to handle - and Vaillant wouldnt publish it.
- Now, if the VR65 is available, and is the only one handling eBUS version 1 (others have got it to work here), then there is a hurdle. Needs work and isnt impossible:
- Arrange your S plan into a two step heirarchy.
- The First level directs opening of flow to HW and/or CH- so you'll need one CH zone valve which is opened by the VR65,
- The CH zone valve then directs flow to one or more of the other zone valves.
- Arrange your S plan into a two step heirarchy.
- You definately need the V3+ EU wireless receiver. Technically as long as the EU wireless receiver is talking in eBUS mode to the VR65, it should all work. The other Tado devices simply inform the wireless receiver to call for heat when they need it.
You have to work this out slowly and in steps. Once all of them are ticked off, the first step is to fit the VR65/VR66 and amend the zone plumbing to work.
The first step is to contact support@tado.com and set out your system clearly as you have here and ask them to escalate this to an eBus experienced officer. Give them these responses, presented here. Ensure that they clearly, and in detail, set out a plan for the migration, using a VR65, or VR66. Tado must confirm that they can interface multiple zones with the VR66 and use the version of eBUS that the VR66 uses.
Also give us a couple of days at this end and will try and find a couple of users who did handle this themselves recently - asking them to engage in this thread.
Once you've got a plan from the geeks at Tado, you'll have a documented pathway, let us know and we will try to locate help in the community, with any unexpected issues you may then hit.
0 -
@wateroakley - thanks for that, I wasn't aware the boiler would modulate even in relay mode, although this makes sense of the different noises and animated flame height on the boiler readout. Maybe there's not so much extra to be gained from ebus modulation as I'd thought, although I'm still keen to work out what benefit can be brought. You curves give a great indication 👍️
@policywonk - I'm happy to play with boiler (and Tado pro) settings to get it to play ball once installed correctly, but still struggling a little to understand the appropriate hardware setup.
- I'm happy on cylinder sensor via either:
- the cylinder NTC sensor seems available for £15 and can be wired in a dry pocket on the outside of the cylinder (so no great shakes) OR
- the VR66 instructions 3.2.6 infer this can be achieved equally with a thermostat
- Do I need a VR71?
- The VR65 is ebus1, available (plumbcentre £95) but seems to be two 2-port valves only (https://professional.vaillant.co.uk/downloads/z/vr-65/control-center-vr-65-installation-instructions-261442.pdf)
- The VR66 (ebus1) is also two 2-port valves (https://www.plumbnation.co.uk/documents/vr-66-installation-manual.pdf)
- The VR66/2 (newer, ebus2 only) instructions also seem to say 2 zones despite chatgpt telling me it's good for 6 zones 🤣 (https://professional.vaillant.co.uk/downloads/product-manuals/vr-66-2/vr-66-installation-instructions-1969891.pdf)
- I see there is also VR70 (2 zones) which is eBus 1 - however I can't find a wiring diagram as it seems to be a more generic device? Do Vaillant make custom wiring diagrams for people, else how does one know how to wire this?
- Then at the ever more expensive scale there seems to be the VR71 (3 zones), but this is ebus 2 (which wont work given your comments)
- I didn't realise I might need to replumb the zone valves into a two step hierarchy (this may be a ball ache due to how the system is currnetly plumbed - close together and not room for more valves!
- From what I understnad the multiple Tados wire their ebus into the Vaillant VRxx? So I keep all the current wired thermostats, I just wire the +/- terminals and lob them all into the VRxx?
Thanks for your help with this - didn't realised this setup would be so unique!
0 - I'm happy on cylinder sensor via either:
-
It’s probably fair to say that if the only tool you have is a hammer, then everything starts to look like a nail.
Regarding Tado and bus systems, they don’t support bus alongside S plan, S plan plus, Y plan or X plan. Using a man in the middle, like a VRx just gives them a single point to talk bus to, like they are driving a combi or system boiler.
Whatever you use as a heating system needs a level of control that matches its level of awareness. I don’t see how your system can achieve that. A well designed system, built with that aim, probably could.
0 -
I'm trying to update a system that was designed and installed before Tado v3+ even existed. The design was effective at the time (S-plan+ with 3 zones using Nest controllers) but since heating costs have increased and our heating needs have changed (with some occupants working from home) I am updating the system to give better zone control by room (rather than by floor).
The Tado system (on relay) is currently working well, but I am openly seeking help to establish if (and how) eBus is possible - my understanding is that some have managed to get this working.
Whether seeking to learn the technical solutions/ limitations on this forum is hammers or nails I'm not really sure ;)
0
