Nest-to-Smiths Heating Control: Live Home Assistant Integration

What changed

The original question was simple: could the Nest thermostat's real heat-demand signal control the Smiths fan convectors without adding another control route to Home Assistant? It now does.

How it works today

The automation watches the Nest climate entity's heat-demand attribute, not its broad HVAC mode. heating means heat demand is active; idle means demand ended while the thermostat remains in Heat mode; and off means heating is off. The automation uses that to control the Home Assistant Smiths controls for both fan convectors.

Unknown, unavailable and unexpected values do nothing. The automation also checks that the heater controls are available before trying to turn them on or off. A switch state is still not independent proof that a fan has physically responded.

Why the earlier test phase mattered

Before deployment, the work used a supervised one-heater procedure: observe the Nest transition, inspect the automation trace, verify one command and confirm the physical result before moving on to the stop path. A separate cycle ending with the thermostat switched off checked that case too.

That staged approach was how I got there, not the end state. It established the demand behaviour and the rules the live automation now uses.

Current status

The Nest-to-Smiths automation is fully deployed and enabled as part of the live Home Assistant heating setup. Both Smiths VE2500 fan convectors are controlled through the ESP32/CC1101 path and Home Assistant controls.

I leave out the low-level radio and access details. The integration itself is not experimental: it is part of the normal heating setup.

Takeaway

For heating automation, the safest route is still a small observed transition first: one actuator, one trace and an obvious way to stop. That trial is now part of the normal heating system.