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

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