{"id":1093,"date":"2017-01-02T08:21:10","date_gmt":"2017-01-02T16:21:10","guid":{"rendered":"https:\/\/partofthething.com\/thoughts\/?p=1093"},"modified":"2017-11-17T21:03:57","modified_gmt":"2017-11-18T05:03:57","slug":"enlighten-your-old-furnace-with-a-raspberry-pi-home-assistant-an-esp8266-and-some-relays","status":"publish","type":"post","link":"https:\/\/partofthething.com\/thoughts\/enlighten-your-old-furnace-with-a-raspberry-pi-home-assistant-an-esp8266-and-some-relays\/","title":{"rendered":"Enlighten your old furnace with a Raspberry Pi, Home Assistant, an ESP8266, and some relays."},"content":{"rendered":"

My mom has one of those on\/off furnaces (EDIT: actually it’s a boiler) that heats up water and circulates it through pipes around the house that have little radiator fins. She wants it to turn on before she wakes up so it’s not so cold in the morning. In this post, I explain how to turn a normal furnace into a smart furnace controlled by Home Assistant for only a few bucks.<\/p>\n

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Furnace controls in Home Assistant<\/figcaption><\/figure>\n

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Starting point<\/h1>\n

I already had a Raspberry Pi 3 running Home Assistant <\/a>for some basic home automation stuff around the house (a few lights, cameras, door sensors, temperature, ham radio, motion sensors.. see my earlier posts in this category<\/a>). This can be set up pretty easily. I also have an OpenVPN server installed on the home router (using DD-WRT), allowing easy remote access to the LAN.<\/p>\n

The furnace is as simple as it gets. There are like 8 zones each controlled by a two-wire (red and white) Honeywell mercury thermostat.<\/p>\n

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Honeywell Mercury Thermostat<\/figcaption><\/figure>\n
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Furnace<\/figcaption><\/figure>\n

Physically Controlling the Furnace<\/h1>\n

When one of these thermostats gets cold, mercury flows downhill and connects the two wires, which are hooked up to a 24V transformer that actuates a water valve (for example, the silver box in upper left of above photo). The water flows and the heat turns on. Again, this system is heat only so it’s as simple as it gets. To take control of it, all I need to do is be able to control a relay that connects the two wires. I could put a relay and temperature sensor in the wall near each thermostat and run some wires to control them, but it’s easier for me to put all the relays together by the furnace and rely on wireless temperature sensors.<\/p>\n

But how to control the relays? I don’t want to have a dedicated Pi down there for run a bunch of wires. Enter… the ESP8266.<\/p>\n