Arduino Central Heating Control (Home Easy Hack)
Firstly, I have no qualifications in electronics, I do not totally understand all the different types of central heating programmers, so I accept no responsibility for you screwing up your system. As I don’t have proper central heating cable, I the colour coding is way off – there are no earth wires, despite the pictures showing earth-coloured wires. This is safe – neither the central heating programmer nor the home easy device need earths, so I use the earth wires as control lines.
However, with that over… I’m on a quest to automate my home with arduinos, and central heating is something that “needs” automating. Yes, I could buy a Home Easy central heating controller for £75, but I already have three plugs and in all honesty, nothing to do with them (yet). After reading an article at instructables, I decided to do something similar but hopefully a lot easier. The final result I aimed for was to have my usual central heating/hot water programmer running as usual, but have the home easy plug sitting between it and the pump/boiler so I could make it act like a thermostat. Then, by leaving the central heating on 24×7 on the programmer, I can take full control over it via arduinos and an AM transmitter. Naturally you could use any home easy remote to control the heating as well, but that’s not very exciting! As I’m prone to playing, I also want to be able to bypass the home easy device and let the programmer work as usual – just in case the code/hardware fails!
So, step one was get the stuff out of the home easy plug (HE302S, for those that care). I could have done what instructables said and ruin a screwdriver to unscrew the tamper-proof screws, or I could use brute force – the latter one. Just pry it open from the end opposite the screws and yank. Then stick a screwdriver by the two clips at the end opposite the plug and lever the circuit board out – much easier!
After probing the wires above (while the programmer was on – had to extend the wires out the bottom), I saw that the right-most pin only went live when the central heating was turned on. Hot water (second from right) went on when hot water or central heating were on. So, all I’d need to do is interrupt the right-most pin, letting it go live when I want C/H, and dead when I don’t.
Left to right, Neutral, Live, Hot Water Off (is live most of the time), Blank, Hot Water on (live when either hot water or c/h is on) and Central Heating on.
The wires in the pic above with red are the new wires that I added, a permanent neutral, a timer controlled live feed (right-most pin) and the output wire from my device.
The home easy device needs a neutral, which I took from the C/H programmer’s neutral, a live, which came from the C/H programmer’s right-most pin – that way the home easy device only gets power when the programmer is telling the heating to go on, which will be 24×7 once I’m happy. And then the output of the home easy device should go back to the wire that was in the right-most pin on the C/H programmer. But, I want an override switch, so put a two-way light switch in the middle of this. Pictures speak a thousand words, so you should be able to see what’s going on in the picture.
I didn’t have to isolate the relay as mentioned in the instructables article – this solution seemed much easier…
Net result was in less than 30mins, I can use a remote or my arduino software to turn on/off the heating – and if all goes wrong, I can take the home easy device out of the loop 