I am as most of you know a great fan of the Sonoff BASIC modules – because, in the main, they are cheap and reliable – but increasingly I’ve been faced with challenges that involve the need for isolated contacts – or high power (immersion heating) or both.
Well, here is my solution – which remains really low cost. The Sonoff BASIC (last but one version) is REALLY cheap at Banggood – and like most other Sonoffs (and other similar devices) it tops out at 10 amps maximum. There are a few devices like Blitzwolf and others which handle up to 16A MAX… but even then, one immersion heater I’m controlling, heats for example the Sonoff TH16 up a little too much for my liking when in a warm cupboard.
Also few if any of these devices have completely isolated contacts (I need that for my thermostat) and all of them switch only the LIVE wire. The answer to all of my problems has been staring at me all this time and I didn’t see it.
Simply take the cheapest option, Sonoff BASIC – and add a 25 AMP contactor from AliExpress – 220v coil (American readers can use 110v verions of all of this)…. 2 poles in my case so you get live AND neutral switching from one Sonoff and one dual contactor – £3.85 + free post for the contactor – right now the v2 Sonoff BASIC is under £4 – I just grabbed some. Add a short piece of DIN rail if you like. That’s what I am doing. It is possible for £1 ($1.40) more to switch up to 63A – I didn’t need that.
You could probably (I will try) make the Sonoff BASIC a bad fit onto the same piece of DIN rail…. the advantage of all of this in my case is 2 screws into the pasterboard wall for the DIN rail, the rest mounts on the rail. If you have a larger set, how about a Sonoff 4CH Pro – which is DIN mounted with isolated outputs – adding in a breaker if and where needed for the extra power.
July 2021 Update
What fun. Well, it all worked – kind of – the contactor wasn’t as good as I hoped and you can kiss goodbye to thoise prices now – but HOLD THE PHONE as Sonoff have a new controller on the way – I have one coming to test… TWENTY FIVE AMPS would you believe.