Can anybody advise with my wiring for thermostat please?

Loosend

Hi, I have a Drayton LZ711Si programmer and a wired Drayton CombiStat. I was thinking I’d just get a wired V3+ and swap the stat over but looking inside it has but 3 wires Brown to Live Blue to 2 and Green/Yellow to Earth.

So thinking I would benefit best from a Wireless system I took the programmer front off to reveal L N Grey (terminal 1) and Black (terminal 3) wires and am now confused as to how the wireless module would integrate and where or if the current wired stat even connects to the existing programmer.

Can anybody suggest the correct wiring conversion from this current setup to either a wired or wireless Tapo please?

My combo is a Worcester Greenstar i.

Thanks
Dan

I can’t upload an image?
I’ve tried a hosting site with a link but not clickable and can’t embed one either

policywonk

Looking at the installation guide: Greenstar i Combi ErP Installation and Servicing Instructions | Worcester Bosch (worcester-bosch.co.uk) this is a more advanced boiler than the Drayton switching system has ever enabled you to access. The boiler has an inbuilt EMS bus which fully expoited saves more money than when it is run in simple switched mode. The Drayteks are however wired as ON/OFF switches, not giving the boiler enough information to run at full efficiency, to throttle its use of gas according to need and save you money. Now you can simply replace the Drayteks in switching mode - which will need some thinking (see recommendations 2 and 3 below), or you can deploy the Tado bits to make use of the unused capacity for efficiency in the boiler (recommendation 1).

Am not a professional, have not worked with this boiler, so three recommendations for you to consider:

1. Contact Tado support, give them all the boiler model details, document the wiring centre next to the boiler, ask Tado for a formal response on the changes to the wiring needed to engage the boiler with your V3+ system. Enact those changes.
2. Contact Worcester technical support - they dont charge AFAIK - for clear instructions on how to get the Tado system to engage the EMS bus. Post their responses here. There are others who will benefit.
3. Take photos of the wiring at the boiler (drop down the lower panel and take the shots), the wiring centre, the Draytek programmer and thermostat - and come back here, posting the photos. We may then be able to decipher how the last installer got it working and suggest the changes you need.

Leaving a message for the Tado administrator @Emcee. By the way, am not a Tado geek, just trying to help.

Hey @Emcee, there seems to be an uptick in Worcester Greenstar boilers needing to be connected via the EMS bus. Could one of the support techs at Tado post a link on this forum to enable that to work? There's a lot of confusion about.

Loosend

Thank you for your considered response. That’s great to know that the boiler can run more efficiently. I’ll find some time as soon as I can to investigate the wiring and add some pics.

Much appreciated 👍

policywonk

Thank you. There are three others working through these issues.

Loosend

I have all necessary images now but can’t upload them. I’m guessing I need to use a desktop to be able to do so?

Loosend

I can offer these individual image links, which will need copying and pasting if that helps?

https://ibb.co/hgGHp51
https://ibb.co/wrS3yJR
https://ibb.co/zfYV7SR
https://ibb.co/6msjbBC

policywonk

1. The picture https://ibb.co/hgGHp51 has five significant wires:
* first three from the left power the boiler.
* grey wire sends Live power to something, probably your programmer, which returns a black wire, offering a call for CH.
* the white wire seems to provide 24/7 authorisation for hot water to be powered when used.
2. The picture https://ibb.co/wrS3yJR is, I suspect, a shot of the E-bus cluster of connecting points. Worcester should, along with the installation guide give you more info.
3. The picture https://ibb.co/zfYV7SR is the combi stat with pin 2 being Switched Live, *Not Neutral* feeding something which is not clear in that it seems to go to another wiring centre or directly to a zone valve. Do you have a box where all the wiring for the boiler, the pump, the zone valve and thermostat get their feeds?
4 The picture https://ibb.co/6msjbBC seems to be the back panel of a programmer with the grey wire coming in from the boiler, the black wire being the authorisation for CH.

Now even if you decide not to use e-bus capacity in that boiler you have enough info to wire in a Tado in relay mode, if you can find where the cables feeding the combi stat come from. It must be a wiring centre near the pump.

Whether or not you elect to run this boiler in e-bus mode, it will be necessary to first find the wiring centre and check to see what it is connected to.
A. Consider dropping the Drayton timer altogether as the Tado app can handle the timetables. When you decide to dump the Drayton timer it will be necessary to isolate and make safe the grey wire and black wire in accordance with Tado and Worcester instructions.
B. Replace the Drayton thermostat with a Tado wired thermostat, but get advice on how the wired thermostat should be incorporated. Use the app to get advice from the support service. May need to get Worcester involved.

Do you have enough to go on?

Emcee

Hello @policywonk

Sorry for the late reply, just got back from holiday.

Sure, I am happy to forward the Worcester Greenstar topic to our tech team. I will keep the forum updated on what they have to say.

Loosend

The advice I’ve been given by somebody is this;

“If replacing the programmer, you already have a brown and blue live there on the N and L terminals, so you'd use those. Grey to COM and black to NO. Then you just need to put the thermostat on maximum. You should have no issues getting that going.
Once you have it working, you could remove the thermostat from the circuit if you can find where it connects in, or connect the thermostat wires together permanently”