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So I'm sure this is going to be a silly question.

Is it possible to connect multiple OpenTherm devices to a single boiler?

I've recently bought an Evohome setup with a modulating OpenTherm Bridge, essentially this : https://theevohomeshop.co.uk/honeywell- ... r8810.html

I'm happy with it, it works. Only issue I have is that I'd like more data about my boiler.

I do have some data using the Evohome provided APIs but it doesn't have everything, for example demand.

Of course after buying all the Evohome kit and getting it going I discover this OpenTherm Gateway!

So I guess I'm asking if it's possible to run an OpenTherm Gateway alongside an existing OpenTherm device connected to the boiler.

I imagine just connecting them both to the boiler terminals isn't going to be a good idea.

The Wireless OpenTherm Bridge just allows the connection of a wireless thermostat to an Opentherm boiler. Basically, the Bridge acts as an Opentherm master. The Opentherm Gateway is intended to be used in exactly such a situation. But you should put the OTGW in series between the Bridge and the boiler. So, connect the Bridge to the Thermostat terminals of the OTGW and the boiler to the Boiler terminals.

That's incredible

So looking at it now, essentially the OTGW is performing a sort of "man in the middle"

So the X1 interface essentially presents as an OT compatible device, I just connect my existing modulating EvoHome OT Bridge to that.

The OTGW can then just pick up all OT related "data/instructions" from the EvoHome and pass that right through to my boiler (on X2).

And similarly data from the boiler just gets passed right back to the EvoHome.

So my modulating EvoHome and boiler will continue working exactly as it was (albeit with the 70ms protocol delay)?

But I will then have the ability to read all the OT data going through the GW for reporting, and if I want (not planning to at this time), override and/or send my own OT instructions to the boiler?

Exactly. And if you don't want any changes to the OT messages, you can even set the OTGW to monitor mode. That will almost completely eliminate the delay.

My mind has been blown, it seems a really well-thought out bit of kit.

Ordered some bits from nodo, cheers!