Wired thermostat installation - no COM port

Adam2102

Hello,

I am trying to wire in a wired thermostat directly to my Greenstar 8000. I realise that this won’t allow for modulation, however, I am seeking individual room control which my current system will not allow.

How do I wire in my Tado wired thermostat directly to the boiler? There are no COM ports…

Rob

My documentation is sceptical about this boiler, but I am not sure. My documentation discusses the Switch Live CH demand connector on page 42. Which won't work with a stat. I think something else might work though. I am seeing this on page 43 of the manual you linked to. The bottom of my screenshot is what I mean. On/off thermostat input.

It can only work if our stat is configured to relay too though. Now if this does not do the trick, I'd contact support.

Adam2102

I should have said - wiring diagrams available on pages 41-43 of the manual - https://www.worcester-bosch.co.uk/support/literature/download/6720883865

KevinBird

I also have this question, as just about to have the 8000 plus boiler installed.

I was wondering if you can still use the Low voltage Analog/Digital to the EMS Connections, even though it may just work like a relay?

if not then could take the 230v output (L) to Tado "COM" terminal, then the Tado "NO" into the Switch Live Return on the Boiler (CH terminal) ?

Adam2102

I ended up using the low voltage Thermostat on/off input terminals and use it as a relay. Works perfectly! My advice is to take the boiler off eco mode as Tado effectively does a basic form of modulation even in relay mode (ie taking into account warm up times etc).

KevinBird

Thanks Adam,

So to confirm.
You have the Analog/Digital terminals in the Tado Thermostat wired into the On/Off Thermostat terminal in the boiler right?
or did you wire the "Com"/"NO" Terminals in Tado to the On/Off terminals in the boiler ?

I read that the 8000+ boiler I'm having installed does it's own internal modulation of sorts, but monitoring the Temp out against the flow return temperature.

Mines also coming with the Bosch Easy Control, but I think I will leave that not connected for now, and use Tado

edit: Thinking about it you must have used the Analog/Digital connections on Tad, since the boiler end is low voltage right?

Adam2102

From memory it was NO and COM as this is what I had used with a previously installed wired thermostat in another property.

KevinBird

Thanks for the Info @Adam2102

My Tado was connected to my old boiler (Worcester Bosch 42-CDI) via EMS using Control D17 (HT-BUS) which worked.

I have just had my Worcester Bosch 8000+ installed. Which from what I've read supports EMS2.
I also read that Tado do not support EMS2.
However…
I connected the Tado Wired Thermostat to the boilers EMS (1) and (2) connections using the original settings on the Tado, and it would not fire the boiler in a call for Heat.
I've switched the Tado to D27 (Bosch EMS+) and the call for heat works now.

So the questions are now.
1) When using this EMS type connection is it going to modulate my boiler?
2) If is doesn't modulate will this override the internal modulation of the boiler (which apparently reads the differential between outgoing and incoming flows)?
3) Should I rewire this and use the "On/Off Thermostat" connections and COM/NO, and use Relay mode (R01) ?