The Efficient Home Forum

Hi,

Does anyone know if the Honeywell ATC928G2000 controller is Opentherm ready like the ATC928G3000 and thus compatible with an Opentherm ready boiler?

Family member purchased it a couple of months ago but installer is suggesting this older model is not Opentherm compatible.

Thanks in advance for any clarification.

Archie32 wrote:Hi,

Does anyone know if the Honeywell ATC928G2000 controller is Opentherm ready like the ATC928G3000 and thus compatible with an Opentherm ready boiler?

Family member purchased it a couple of months ago but installer is suggesting this older model is not Opentherm compatible.

Thanks in advance for any clarification.

They are all compatible with the OpenTherm Bridge R8810A, right the way back to the G1000 model.

Thank you very much for the reply and confirmation.

Unfortunately, Evohome doesn't seem to be compatible with the Opentherm ready Baxi 600 combi and Baxi's own interpretation of Opentherm. Basically, Baxi lockout the flow temperature controls on the boiler panel when connected via Opentherm and these default to a maximum of 80c for DCH and 60c for DHW.

The assumption made by Baxi is the Opentherm controller takes over the control of DCH and DHW flow temperatures, hence the lockout, but the Evohome does not provide an option to set these as you require, such as 55c for DCH and 45c for DHW, so with this combination, you're left with a very inefficient 80c on the heating side and a scalding hot 60c on the hot water side. What a joke!

I believe both Nest and Tado both allow these adjustments from the controller side, so I'm shocked Honeywell haven't incorporated this feature into Evohome.

After a day of researching and a number of HR92 controlled zones to take into account, it looks like they will have to keep the Evohome, forget Opentherm, revert to a BDR91 and incorporate Baxi's own weather compensation kit, which is fortunately only £30 and fits into the flue. This will at least reinstate control over maximum flow temperatures.

Happy to hear of any alternatives if they exist.

Cheers.

Archie32 wrote:Thank you very much for the reply and confirmation.

Unfortunately, Evohome doesn't seem to be compatible with the Opentherm ready Baxi 600 combi and Baxi's own interpretation of Opentherm. Basically, Baxi lockout the flow temperature controls on the boiler panel when connected via Opentherm and these default to a maximum of 80c for DCH and 60c for DHW.

The assumption made by Baxi is the Opentherm controller takes over the control of DCH and DHW flow temperatures, hence the lockout, but the Evohome does not provide an option to set these as you require, such as 55c for DCH and 45c for DHW, so with this combination, you're left with a very inefficient 80c on the heating side and a scalding hot 60c on the hot water side. What a joke!

I believe both Nest and Tado both allow these adjustments from the controller side, so I'm shocked Honeywell haven't incorporated this feature into Evohome.

After a day of researching and a number of HR92 controlled zones to take into account, it looks like they will have to keep the Evohome, forget Opentherm, revert to a BDR91 and incorporate Baxi's own weather compensation kit, which is fortunately only £30 and fits into the flue. This will at least reinstate control over maximum flow temperatures.

Happy to hear of any alternatives if they exist.

Cheers.

There is nothing really to be shocked about here, as OpenTherm controls are not required to provide DHW or Max Flow Temp control and if they don't provide it, the boiler is supposed to allow this adjustment on it. As you have stated, Baxi don't allow this but this is no mistake and I believe they have done this purposely so they don't work with the bulk of OpenTherm controls in the market. Very poor show of them indeed and why I do not recommend Baxi (why would anyone fit one anyway, as the specs verses others are dire).