HVAC, Thermostats & IR Climate

The "I have a mini-split and I want it on a schedule HA controls" page. For the hub above this layer see Smart Home Hubs; for ESP firmware see IoT Firmware Platforms; for the bigger industrial protocols (Modbus, BACnet, KNX) see Industrial IoT Protocols.

IR-controlled mini-splits / window units

The bulk of consumer climate hardware uses IR remotes — and an ESP32 with an IR LED can pretend to be that remote.

• ★ ESPHome climate_ir / heatpumpir — built-in component that supports 30+ heat-pump brands (Mitsubishi, Daikin, Panasonic, Toshiba, LG, Hisense, etc.) over IR. ESP32 + 940 nm IR LED + transistor + maybe a receiver to read remote codes. Cheapest possible "make my dumb mini-split smart."
  • https://esphome.io/components/climate/ir_climate.html
• ★ Tasmota IR transceivers — Tasmota IR-bridge-class hardware (Sonoff Bridge with IR mod, or generic ESP+IR) sends/receives IR with HA remote.send_command.
• Broadlink RM4 Pro / Mini — closed but loved Wi-Fi IR/RF blaster; HA integration. Good for "I have 6 different remotes in this room."

Mitsubishi / Daikin / Fujitsu local serial integrations

When IR isn't enough, talk to the heat-pump's internal CN105 / S21 / X50A / etc. service connector.

• ★ mitsubishi2MQTT / MELCloud-local — many Mitsubishi mini-splits expose a CN105 service header; an ESP32 wired to it gives bidirectional state + control; far more reliable than IR.
  • https://github.com/SwiCago/HeatPump
• ★ Daikin S21 — Daikin's serial protocol; ESPHome / Faikin firmware reads/writes natively; HA integration. Way better than IR for Daikin units.
• Fujitsu / Toshiba / LG — most have similar service ports; ESPHome external components for each.
• MELCloud (Mitsubishi cloud) — closed cloud API; HA has an integration; works but cloud-dependent.

Hydronic / boiler / OpenTherm

• ★ OpenTherm Gateway (OTGW) — DIY board / kit that sits between a thermostat and an OpenTherm-compliant boiler; reads / overrides setpoints. ESPHome / otgw-mqtt firmware. The standard for European combi boilers.
• Diyless OpenTherm Master Shield — pre-built OpenTherm interface for ESP32; MQTT firmware available.
• Tado / Honeywell evohome / Nest — closed thermostats with HA integrations; varying local-control success.

Smart thermostats

• ★ Z-Wave thermostats (Heatit, Honeywell T6, Aeotec Radiator Thermostat) — Z-Wave is the right radio for thermostats: low power, locks-in, mature. See Z-Wave Stacks.
• ★ Aqara / Sonoff TRV — Zigbee thermostatic radiator valves; cheap; pair via Z2M.
• ecobee — Wi-Fi; local API now exposed; HA integration uses cloud auth + local fetch; one of the few cloud-thermostats that play nice.
• Nest — post-Works-with-Nest, the third-party API is very limited; HA integration via Google's Smart Device Management (SDM) works for Nest Thermostat E / 3rd / 4th but is fragile and Google has a history of cutting off access.
• Tado — closed cloud only; good UX; no local fallback.
• Sinopé (Quebec) — Z-Wave / Zigbee thermostats; great for line-voltage baseboard heating.

Floor / radiant / specialty

• Heatit Z-Push / Z-TRM — Norwegian; Z-Wave; the floor-heating thermostat.
• Mysa — Wi-Fi line-voltage thermostat for baseboards; closed cloud.
• Devireg Smart — Danish; Z-Wave floor thermostat.

Sensors that pair with HVAC

• ★ Aqara T1 / TVOC sensor — Zigbee temp/humidity/VOC; ubiquitous.
• SCD40 / SCD41 + ESPHome — accurate CO2 sensor for "is this room making me drowsy."
• AirGradient ONE / Open — open-source IAQ monitor (PM2.5, CO2, temp, humidity, VOC); HA integration; Pro version sold by AirGradient.
  • https://www.airgradient.com
• PurpleAir — outdoor air quality; closed cloud; HA integration via API.

Practical guidance

• ★ Check for a service serial port before resorting to IR. Most modern mini-splits have one; finding the cable is a one-evening project; reliability is night-and-day better.
• Pair humidity to your thermostat automation. "Heat to 21 °C OR if humidity > 60 %, run dehumidify mode" beats temperature-only.
• Don't put a temp sensor over a vent or in direct sun. Calibrate against a real thermometer once.
• Per-room setpoints + smart TRVs > one whole-house thermostat. Even with a dumb boiler, smart TRVs unlock zoning.
• Heat pump efficiency drops below outdoor design temp. Cross-check with weather; HA can switch heat sources via Met.no forecast.

Pick this if…

• Smart mini-split, easiest path: ESPHome IR climate.
• Same mini-split, reliable path: ESPHome + service serial port (CN105 / S21).
• European combi boiler: OpenTherm Gateway.
• Cheap per-radiator: Aqara / Sonoff Zigbee TRVs.
• Whole-house Z-Wave thermostat: Heatit (EU) / Honeywell T6 (NA).
• Air quality: AirGradient ONE.