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I consider using OpenTherm Gateway, but I'm unsure whether my boiler is supported.

I have an ATAG E 325C boiler, which contains a blue ATAG Z sticker (see picture). This implies the boiler is using the ATAG Z-WAVE protocol. However, I read here and there that OpenTherm and Z-Wave are similar. Additionally, the thermostat I'm using is a ATAG Wize and the (online) manual states: "De WiZe klokthermostaat communiceert met de aangesloten CV-ketel via de ATAG Z-bus (OpenTherm)". I interpret this as an additional indication that my boiler supports OpenTherm, but I'm not fully sure.

Hopefully anyone can give me confirmation whether OpenTherm Gateway is the right thing for me. Thanks!

Z-Wave is a wireless protocol that is something completely different than Opentherm. The ATAG Z-bus on the other hand is supposed to be similar to Opentherm. It is intended for an ATAG Z-thermostat (EaZy or WiZe). The manual for the boiler specifies that aside from these thermostats, any Opentherm thermostat can be connected to positions 1 and 2.

The equipment matrix shows that users have uploaded logs for both an ATAG E325EC boiler and an ATAG Wize thermostat. This is a further indication that the Z-bus is compatible with the OTGW. I realize you have a slightly different boiler. But according to the manual the only difference is that the E325EC has an additional heat exchanger. That is not going to affect the communication protocol.

Obviously, I won't give any guarantees, but I'd say you stand a really good chance that the OTGW will work with your central heating system. Whether it is the right thing for you depends on what you want to use it for.

Thanks for your reply and apologies for confusing ATAG Z-bus and Z-Wave.

I'm not an expert in this area, but from what I understand based on information found online there are different versions of the E325C boiler. This overview by Plugwise for example shows that E325C boilers manufactured after February 2013 do support OpenTherm, while boilers manufactured between April 2009 end February 2013 use the similar Z-Bus. My boiler was manufactured in 2012 and thus uses Z-Bus.

The equipment matrix indeed provides some indication, but the manufacturing date of the ATAG E325EC boiler that was used for this matrix is unknown (I saw the date 2014-08-19 on the details page but I assume that's the measurement date). Assuming the E325EC is similar to E325C, the chances are high that the manufacturing date of the E325EC is also relevant with regard to OpenTherm support.

In any case, complete guarantees are not possible and I certainly do not expect that from an open source project. Thanks again for your thoughts. I'll probably just give it a try and then report back on my experience later.