Evohome, Opentherm gateway, hot water command

[deuscreator]

Hey folks,

Here's the deal: Evohome wifi system with 3 underfloor heating zones, 7 radiator valves, connecting via Opentherm relay / gateway to a BAXI Luna DuoTec 1.24 heating boiler. Modulation, etc. seems to be working fine.

The issue is, that I wanted to add a hot water kit, and the boiler has an internal hot water valve that in theory could be activated via an opentherm command (make hot water), but the Evohome only sends a 100% boiler firing setting and a command to a BDR91 to operate a non-existing motorised valve to divert the hot water from the boiler through the DHW cylinder.

Now, is there a way to make the Evohome send a make hot water command instead? Via Domoticz? Via an usb-based gateway (hgi80)? The Baxi boiler has it's own Opentherm-based thermostat that can handle this, and the problem is worsened by the fact, that when an opentherm gateway is connected to the boiler, the manual controls for the hot water are locked, and the boiler expects Opentherm commands to make hot water and to operate the internal valve..

Any ideas welcome!