Greenstar 27 Ri with eBus wiring centre installation

simo_newm

Hi,

I have read conflicting information whether Tado is compatible with this boiler. It says all Worcester boilers are but when I go to installation instructions on the app it just errors out.

From what I have read Tado can talk the eBus language of these boilers but only if you have the EU version of the wireless stat or a non EU version with an extension kit but I have seen that this might no longer be the case and you have to look for old kit on eBay?

I have had an engineer say it's easier to install a new wiring centre (a relay only version I guess) but would like to know if I can get it working as is if possible.

I have (photos attached):

Worcester Greenstar 27 Ri Boiler
Greenstar Ri Professional Wiring Centre (near the cylinder, a long way from the boiler)
S-Type Plan setup
Current wireless thermostat is an old Comfort one or something but completely broken

I'd like to get it working with eBus modulation if possible but would be happy with just a relay setup. Any help would be greatly appreciated.

Thanks,
Simon

simo_newm

In the end I've gone for the relay system over IZ3 with the wireless v3+ stat for a few reasons:

1. Easier to wire in as the stat and the wiring centre are on different floors and a long way from each other.

2. I'm going to be adding loads of Tado TRVs tomorrow and worried even if I get HT_BUS working, the more things I add the more likely it's going to go wrong.

3. I think (but I could well be wrong) that modulating the boiler is going to have less effect when I set up each room as zones with TRVs as each zone is likely to be set to different temperatures.

4. I am a software engineer, and although I'm sure the Tado guys have done a great job reverse engineering the HT_BUS coding, with Bosch not supporting it, it wouldn't surprise me if less than 100% of the bus coding commands have been discovered.

It all worked first time, which is suspicious but installing was very straight forward. The Tado support above said it wouldn't work with current DT 20 RF, but it does as long as you force the CH to be permanent ON.

I actually got the stat that controls hot water too and put it into 'combi mode / yellow led' as it was cheaper and I thought more future proofed. When I think about it, I don't see why I can't connect L on PZ1 to HW COM on Tado and HW NO to L on the HW valve and set HW to constant on on the old controller. That way the wiring centre still has master control by using the tank stat but Todo should then be able to schedule water on and off.

Anyway, thanks very much for you help. I'm sorry I didn't get to test the HT_BUS. I'm sure it would have worked but I do feel more comfortable with this setup.

Thanks,
Simon

policywonk

Have gone through both the manuals, ie the boiler and the wiring centre. The connection at IZ3 seems to be key to enabling this to work at all. I see that it has been bridged across the pins - and therefore it should fire.

Have you considered this?

• Perhaps one of two port valves has failed to complete the connections needed to enable the boiler to fire.
• Does the valve switch over when you turn it on, or does it just sit there and do nothing?

Seeing that you've done so much of the homework, perhaps a talk with the manufacturer's tech support team may be worth your time; to have them tell you what specifically is needed to put it into relay mode, at least on the CH side.

Small thing...Was the whole system deliberately turned off when you took the shot of the timer/programmer? Wondered why there was nothing on display.

simo_newm

Thanks, I haven't tried installing anything yet. I just wanted to know if Tado would work with this system. It currently still has it's original controller installed in the boiler which is working for the hot water on timer, for heating I have to manually turn heating on and off. I thought maybe setting up Tado to control IZ3 would work for the heating but I would also like it to control hot water too. I get a bit lost when it comes to how the eBus modulation works so not sure about the compatibility. Yes I had turned off the system so I could get to the wiring to take photos. Thanks, Simon.

Rob

The Greenstar Comfort uses a digital HT_BUS interface, as does your boiler. At least, that is the naming in our documentation, it might be named differently elsewhere. We support this bus with V3+. You mention your old Comfort is a wireless thermostat. Does it have a wireless receiver connected to (or mounted in) the boiler or wiring centre? If it does, you simply need to select that specific Comfort wireless receiver in the tado installation instructions for the tado wireless receiver. You will then get instructions, in the app, to replace that wireless receiver with our wireless receiver. Retaining the modulating interface and no need to do difficult wiring.

To simplify: It is moot to what device (boiler, wiring centre, whatever) the Comfort wireless receiver is connected. We would re-use that wiring and connect our wireless receiver in the same way.

This is in theory, as I do not know for sure which of the multiple Comfort wireless receivers you have.

simo_newm

Thanks Rob. I got told it was a Comfort stat but I just went to check and it doesn't say anything on the receiver or stat apart from Worcester. I opened up the receiver and the model number is DT 20 RF Receiver. When I put this is the Tado app it shows up but doesn't give any instructions. See attached. Thanks, Simon

policywonk

Would you check whether, when you call for heat manually, whether the zone valve changes its lever position please?

As I understand it, the DT20RF thermostat was not working. However what I find odd is the fact that the IZ3 pins have been bridged even though you havent installed the Tado system. According to the Greenstar manual, the IZ3 pins are bridged only when you arent using Greenstar's products- but the profile suggests that nothing not from Greenstar has been installed - unless that DT20RF is non standard, but I suspect not.

You have three options. One is to call Worcester and ask them for specific instructions to fit a Tado based thermostat system.

The second is to get hold of a multimeter to measure the voltage levels on these points:

• PZ2,
• PZ3,
• IZ3

The measurements have to be taken on each pin with CH off, then repeated with CH on. Come back, or relay this information to Worcester.

The third option is to get a heating specialist electrician to help out, if you are worried about time.

simo_newm

Thank you very much. I will ring Worcester and ask for instructions! Happy to get an electrician if I can find one, but one guy wanted to replace the whole wiring centre and another guy said it took him 2 days last time he tried to install one so recommended I find someone else!

policywonk

Hi. Been studying your pictures and the installation guides carefully.
1. From the photos you seem to have three zones (HW, and two CH zones).
2. You seem to have two WIRED thermostats (one or both may have a wireless proxy), but one is wired into IZ1, another into IZ2.
3. IZ3 has been bridged to inform the wiring centre that the third thermostat position is bypassed.

Would you have a look at this thread please?
https://community.tado.com/en-gb/discussion/22106/greenstar-28i-junior-combi-mk-iv-tado?utm_source=community-search&utm_medium=organic-search&utm_term=greenstar

@wateroakley got involved. There are parallels. It eventually refers to a need to unplug that programmer and it's ribbon.

Does it help? Can you get something to measure the voltage on those pins? We need to clarify whether those pins are in 240v mode or 24v mode.

Happy to think with you.

simo_newm

@policywonk Thanks, but was there meant to be a link to another thread?

policywonk

Hi. Updated it to ensure the link is there. You'll see from the link to be careful to not bridge 240v on pins that are only expecting 24v. Measuring the voltage in the different modes is important.

I've also edited the last post.

simo_newm

Thanks for looking into this. This is what I think is happening.

IZ1 us HW valve end switch which signals boiler to fire when valve is fully open
IZ2 is CH limit switch which signals boiler to fire when valve is fully open
IZ3 is input for thermostat which Tado would connect to

PZ1 and PZ2 connect to valves to open and close them.

The bit I don't understand is there doesn't seem to be a way to control the hot water. I can only assume I leave current built in controller on boiler to set the hot water on/off and use Tado only for heating. I'd guess I'd have to leave CH controller on boiler to always on too and let IZ3 control it.

I might be completely wrong and if I am it would be great to know that!

Thanks,

Simon

simo_newm

Or can i connect the Tado stat directly to the valves which will then in turn call for the boiler to fire when open?

policywonk

This link- https://www.worcester-bosch.co.uk/support/literature/download/release/6720810965/12547
- makes it plain that the ebus (or ems bus) is the way that the Comfort thermostat or programmer is fitted.
- the wiring centre contains the temperature control on the hot water tank

Having read other literature, it suggests that the inbuilt timer in the lower right of the booklet actually has primary programming rights. It is connected to the ebus via a ribbon connector.

I believe, but Worcester will have to confirm this, that your wired tado stat could wire/ serve in its most basic relay mode when wired to the IZ3 or as an Ebus stat by connecting to one of the spare ebus connection points.

It is possible that your old timer would need to be disconnected from the ribbon behind it. But the manufacturer would help on that. This may actually be a 45 min job!

Did you manage to check the voltage readings on those pins?

simo_newm

Thank you @policywonk
I can confirm that when you I for heat manually the the zone valve opens (I can hear it and the water starts flowing). I think the actual lever position only moves fractionally though.

As for the voltage readings I have:

• PZ2 - 240v when heating on, 0v when off
• PZ3 - 240v when heating on, 240v when off for about 3 minutes then 0v
• IZ3 - 240v all the time

I don't have any wired thermostats wired into IZ1 and IZ2. I thought these are wired to the valves so the valves can report when the valves are fully open and call for heat?

I have sent off photos and descriptions to Worcester tech support but haven't heard back yet.

It would be great if I can connect via eBus to one of the spare eBus connection points in the wiring centre. I can't find any documentation at all on what those points are meant to do though.

Was that link to the other thread correct as I can't find anything on there that refers to this bit: "It eventually refers to a need to unplug that programmer and it's ribbon"

Thanks again,

Simon

simo_newm

Here's the response from Bosch technical support. Looks like I'm out of luck :(

"Thank you for your enquiry.

There is no option to use a Non-Worcester compatible control with the Greenstar Wiring Centre. You can replace the existing programmer and thermostat with a more advanced control, specifically our Comfort II RF (7733600002) but not a smart control without removing the wiring centre.

IZ3 is not a terminal which is used in the UK but does have use in Europe. The programming is disabled on UK models.

Best regards,Technical Support(HC/SGB-I2R-TC)"

policywonk

@Emcee

@Rob

Would you both please look at this thread and in particular Worcester Bosch's response to @simo_newm?

• @Rob you were clear that the E-bus could be engaged (I presume either with a Tado receiver or a Tado wired thermostat).
• There is this thread EMS bus support UK - Page 2 — tado° Community in the community, which suggests there are glitches and that clarity from Tado has been a challenge.
• Now, given that odd response, are you in a position top please could the support team clarify: (a) Is an E-bus connection still viable on this system? (b) Specify the wiring to make that work.
• If you aren't certain, please provide @simo_newm with the wiring instructions he needs to fit in relay mode.

@simo_newm. Am genuinely surprised. Am sorry that I gave you wrong link identifying what to do with the programme- cant seem to find it now. Must be getting old. Anyway, some suggestions:

1. Please consider writing back to Bosch re-quoting the case id and ask them to clarify again their response, stating the following (a) that Tado made it clear that their system does communicate with the E-BUS and is effective in the UK (b) that you need to know if this can be done with the existing Greenstar wiring centre in place, or whether it needs to be removed and (c) if necessary, what steps need to be taken to update the firmware on your boiler to enable full control over the EMS-bus.
2. If you've had enough of this bouncing around and just want it working, come back. If nobody from the Tado side of the community responds, tell me and will do my best to work through the wiring again to help you set the Tado system up in Relay mode.

simo_newm

Thank you @policywonk. I have written back to them and asked them to clarify. To be honest I'd be happy to go with Relay mode. I'm guessing from what I've seen that even then I will only be able to control the central heating and not the hot water.

I really appreciate all your help on this.

policywonk

Ok. I'll stop and read the instructions again when am back tonight and come back.

policywonk

You are right. IZ3 should fire the boiler in CH mode if bridged. You said you can manually force it on. How do you do that?

policywonk

Your wiring centre has the right I settings- S Plan. Our only risk is whether Worcester say the wiring centre must be replaced if we run this in relay mode.
* However I think you worked that out a long time ago and got the system to work by bridging IZ3. Do I presume right that when you wanted to manually turn on the CH, you'd bridge IZ3?

That aside :-) if my mind has it right, all you need is one Tado wired thermostat
1. Configure it for relay mode, connect it to IZ3:
* Live on the IZ3 to COM on the Tado stat
* IN on the IZ3 to NO on the Tado stat
2. Marry it with your internet bridge (just in case)
3. Turn it right up to 30. The boiler should fire, trigger the CH zone valve and start the CH pump.
4. If that works, you'll only be controlling CH, the wiring centre will still control HW.
5. Then configure the wired thermostat in the app. Decide if it works and then prove to yourself that it can be shut off or on, using the App.
6. Decide whether you need to add smart TRVs.
7. Sit tight and wait for @Emcee and @Rob to come back with the guidance on what to do. At least for now you'll be functioning.

Here's the link to the DT20RF Mk1 programmer.
https://www.worcester-bosch.co.uk/professional/support/literature/worcester-dt20rf-installation-instructions

From the information you provided earlier, a manual trigger of CH operates the 240v side of things easily. In this case, I suggest you set the CH programmer side to be permanently ON. This should prevent the E-BUS turning the CH off when the Tado App says it should be on.

And by the way @Emcee is back in town! He's offered to talk to the support team and keep us updated on this.
https://community.tado.com/en-gb/discussion/comment/84155#Comment_84155

policywonk

Whilst we are waiting for the Tado team to come back, if and when you get the time - this isnt urgent - would you:

1. Confirm that TC1 fitted on the right hand bank, of the wiring center, goes back to the hot water tank?
2. Check the voltage across it when the boiler has a call for heat to HW. Use a real high impedence multimeter if you have one, is the voltage somewhere 3-25v and flips around?

If it is, the solution to making E-bus work may actually be simple, however we need to wait for Tado to tell us, otherwise I run the risk of blowing your new wired stat!

Page 14 of the Greenstar wiring guide has a picture which may solve it. The unused BUS connector is where the Tado may work, wired in, in digital mode.

policywonk

I forgot. There is a link on the main boiler connectors, ie a brown wire between live (L) and (LR) - which is Switched Live or Live Return.
Having studied the circuit, it seems that when this link is removed CH control is then passed onto to the wiring centre.

This means that if having taken 3 of the 7 steps given further above, if there is still no result with IZ3, please remove this link, it should enable the wired stat to run in 240v relay mode.

simo_newm

Thanks so much for looking into this. I manually force it on just by holding down the OK button on the DT20RF receiver as the thermostat won't connect anymore. This is enough just to keep it on constant.

I haven't heard back from Worcester yet but will try the things out you said this evening. I never bridged IZ3 myself, it's been like that from day one. Shall I try putting the heating on constant and then removing the bridge on IZ3 to see if the heating cuts out in the meantime?

I can also confirm that TC1 goes back to the hot water tank as I had to replace the sensor a while ago.

Thanks,

Simon

simo_newm

Also I was going to ask, can I get the EU version of the wireless thermostat which has the digital contacts instead of the UK wired one? The wiring centre is on a different floor and quite a way from where I want the stat to be.

policywonk

There are two options you have to consider.

1. The existing wired receiver (of the DT20RF II) has a receiver, which uses actual the E-BUS to tell the wiring centre to trigger the zone valve in your home - it does this 30 seconds before it calls for the boiler to start.
   1. If you have it in relay mode then you will need a wired switch to force that zone valve to move.
   2. If you have it in E-bus mode, then the Greenstar centre and theoretically a wireless stat should work. This is seeming @Rob's domain. Apologies @Rob if am calling your name in vain.
2. If you elect to keep it in Relay mode, you will nee a wired Tado thermostat or the Tado EU wireless receiver, wired to do that for you and also triggering the zone valve.

There is a third option. the Wireless Receiver which was originally used in the UK, I believe the model is EK01-TC-UK-03, is capable of running a digital interface and there are some still on sale on Ebay. It is possible that @Emcee and @Rob will conclude that am being naughty and that you are better off focused on Options 1 and 2.

@Rob this is your domain. Which would you recommend?

And all that aside, it is best, if you can handle this, over the next couple of years, to fit smart stats on all your radiators (except the one closest to the boiler). Each room has different needs and you'll find that you can recoup your costs within 3 years. Screwfix and Amazon have seasonal windows where they do deals on TRVs.

Rob

@policywonk I have to come clean in that I am more familiar with continental European setups. With wiring centers and other very UK-specific things, I'm out of my league. My suggestion would be to contact our support for help. There you will find people who are more experienced with these types of heating systems than I am.

Controlling this boiler in a modulating way (assuming issues with the wiring center are solved) would require an EU-market wireless receiver (serial number starting with BR), its predecessor the Extension Kit (serial starting with EK) or a wired V2-V3+ Smart Thermostat (RU). The UK wireless receiver (BP) only has relays and no support for digital busses. The EK was available in all markets but has been discontinued multiple years ago. The V3+ Smart Thermostat is still available, including in the UK.

policywonk

@Rob My bad. Thank you for the input.

@simo_newm Rob's recommendation is plain. Time to push the Support team for a clear response. If they don't come back and you can be careful this link may help -

https://cdn.brandfolder.io/607DGEMS/as/7k4rssnm8hbmr6mjf94qmck/104210-DIGITAL-ST01IB01-INSTALLER_MANUAL-TA-EN-00-V3.pdf

It applies when fitting a Tado Wired thermostat to an EMS BUS on a Bosch Worcester boiler. As you seem to be thorough, I know you'll think this through. Note that there are 2 spare bus connector points on the wiring centre. The wired thermostat should work, screwed into the one to the left of the one currently in use.

Here's the risk of it going wrong. The best case scenario is that it will start and stop the boiler correctly, and throw the valves correctly, along with starting and stopping the pump. The second best scenario is that the boiler starts and stops, turns the heating valve open and shut but forgets to turn the pump off. The third is you sit there and nothing happens. It comes down to the version of firmware, some of the earlier ones had bugs- and Tado's digital compatibility also has limitations. I believe you will have one of the first two results - as all the threads on this forum point to that.

• It seems that there are many versions of the firmware and some forget what to do when instructing a boiler to turn off its call for CH heat.
• I suspect that Tado are being quiet because this information is partly in Worcester Bosch's hands, not Tado's.
• The serial number of the boiler will inform Worcester which EMS-BUS firmware version you have - and they know how to update it. I called Worcester's tech team and they informed me that when the boiler is serviced you can ask to have it brought up to the latest firmware when their team service it. Third party heating agents don't often have the certification to be trusted with the downloads, but they can advise on a local firm which can help. Must have been lucky today.
• In short you have to try it out yourself at some point.

@Emcee will likely be doing his best in the background to expedite a response for you.

Ebay has two of the EK01-TC-UK-03 wireless receiver for sale right now. The Wired thermostat will support more versions of the EMS BUS though.

Good luck. I think you have enough to take a step and meet a stranger!

Will be here.

simo_newm

Thanks so much! I'll give it a go with the eBus and the wired thermostat. The only problem is when I went to buy it here: Tado V3+ Smart Wired Heating Thermostat Starter Kit - Screwfix it says it's only compatible with combi boilers and someone from Tado seems to confirm that in the Q&As on that page. Are there multiple versions of the wired stats?

policywonk

I think that's because it plays no role in calling for HW. You having the option to return to screwfix within a year.
Here's another link I found
https://community.tado.com/en-gb/discussion/15094/ems-bus-support-uk/p2
Looks like this isn't a big deal.

policywonk

According to @Rob you may have the HT_BUS not the EMS-BUS. you may have to try the HT_BUS, ie D17 configuration first.

simo_newm

Thanks @policywonk, will do. When I test the digital connections should I leave the old controller in the boiler and if so, what settings? Do I need to remove the IZ3 bridge or the bridge on the boiler connections? Thanks!