My Smart Thermostat Runs Boiler, Mini-split, And Window A/c

About the project

The project will start, control, and protect a wood-fired boiler, modulating according to outdoor temperature. It will control a mini-split to provide heat or cooling. It also controls a window A/C. Statistics are rendered on Blynk graphs. Control via Blynk and Node-Red dashboard.

Giant Board SBC Contest WinnerGiant Board SBC contest winner

Project info

Difficulty: Difficult

Platforms: AdafruitBlynkIBMNodeMCU

Estimated time: 1 day

License: GNU General Public License, version 3 or later (GPL3+)

Items used in this project

Hardware components

Groboards Giantboard Groboards Giantboard Central controller x 1
NodeMCU v2-Lua based ESP8266 development kit NodeMCU v2-Lua based ESP8266 development kit Heat valve controller & water heater monitor x 1
Witty ESP-12F Witty ESP-12F Mini-split controller x 1
Wemos D1 Mini Pro Wemos D1 Mini Pro Window A/C -- external antenna selected for best WiFi reception x 1
High current (30A) relay High current (30A) relay Window A/C compressor x 1
Relay board, four channel Relay board, four channel Boiler, heat valve, and window A/C x 3
Groboards WiFi Featherwing Groboards WiFi Featherwing x 1
Temperature Sensor Waterproof (DS18B20) Temperature Sensor Waterproof (DS18B20) 3x boiler, 2x window A/C, 1x water heater x 6
ESP-01 ESP-01 Attic fan controller x 1
Outlet Outlet Boiler, attic fan x 2
Box fan Box fan Attic fan x 1
Outlet box Outlet box Boiler, attic fan x 1
Vera Hub Vera Hub To read Z-Wave thermostat x 1
Eko Boiler Eko Boiler x 1
Mini-split Mini-split x 1
Window A/C Window A/C x 1

View all

Software apps and online services

Blynk Blynk
Node-Red Node-Red
MQTT server MQTT server subscription subscription Automatically control your temperature anywhere in the world!

Hand tools and fabrication machines

Soldering iron Soldering iron x 1
Connecting wire Connecting wire x 1



Wood is the most renewable and plentiful energy source in some places. But burning it can produce lots of smoke and ash. Enter a gasification boiler. It bakes the wood and burns the gases for very little smoke or ash. It's like carburetors versus fuel injection. Of course, a wood fire isn't so easy to turn on and off, and boiler must never overheat because they could explode. A mechanical thermostat, costing about $100, was the typical answer to the problem. But a post by David Hunt started me on a cheaper, "smarter" path.