Updated 18th February 2025

Experimentation – Work in Progress

I have an Ideal Vogue Max 18kW System Boiler with Weather Compensation, using Hive to control the schedules and room temperature, I also have individual radiator Hive TRVs but these are set to 23^oC to limit overtemperature, ideally the system is set to ‘open loop’ control.

The above graph from Open Energy Monitor shows my systems efficiency over the period to be between 98% and 74% and I read that utilizing Opentherm Gateway hardware with Smart Autotune Thermostat integration in Home Assistant could make energy efficiencies, hence this blog.

Overview –

Outline system proposal trying to retain the Hive control for timing schedules for hot water and heating whilst using opentherm for greater gas modulation control on heating, rather than the Hives’ on/off control.

Project Information Sources –

• Opentherm Gateway Project
• Opentherm Gateway Forum
• Smart Autotune Thermostat – Github
• Home Assistant – Custom Component Forum

Opentherm Gateway (OTGW) – This was bought from Nodo-Shop, I chose the Wi-Fi version and paid to have the WeMos D1 Mini Wi-Fi module pre-programmed, I also bought a case for the completed gateway.

The PCB needed a small amount soldering, but they also offer this service.

• Link to Gateway Assembly Instructions
• Link to Enclosure Assembly Instructions

Completed OTGW and Ideal Halo Lite thermostat.

The OTGW can connect to OM Monitor which reads the opentherm traffic, in my case the boilers return water temperature was not being read for some reason, within the Gateway Project writeup, there is matrix showing compatible thermostats and boilers, I took a chance as my boiler wasn’t listed 🙁

More to follow…….