How to utilize On/Off Thermostat with OpenTherm Gateway and prevent overshoot


I have an MCOHome MH7H (Zwave) room thermostat (on/off), connected to (Schelte Bron) OpenTherm Gateway, connected to my Remeha boiler. All communicating well with HomeAssistant and working as expected - sort of.

My issue is that the MCO room thermostat has a 0.5C hysteresis, and only allows temperature selection in steps of 0.5C, which results in a massive overshoot. I.e.: when the room is 18.9C and I want it to be 19.5C, I need to set the request temperature to 19.5C (as 19.0C is insufficient delta - only 0.1C - to switch on the boiler). Asking 19.5C causes the boiler to go on, only to go off again once the room temperature reaches 20.0C (again: >0.5C hysteresis). That then results into on overshoot up to 21.0C, as the room keeps heating up for quite some time, and an unhappy ‘CEO’ in the house :slight_smile:

I would really like to physically disconnect the thermostate from the ‘thermostat’ input of the OpenTherm gateway, have a software solution that reads the request temperature and actual temperature from the MCOHome thermostat (using the Sensors and Controls already visible in HA), and subsequently use those values to modulate my boiler via the OpenTherm gateway.

I spent the last 2 days reading about OT Gateways on this forum, but have not been able to find a solution that fits my situation and existing components. Any pointers would therefore be much appreciated!

Many thanks,