Immersion Heater Switch (UK)?

Hi. I want to automate the electric switch on my immersion heater. So I am looking for a smart switch powerful enough to handle the draw of a water heater.

Something like this one.

Sadly the timeguard one does not appear to work with smart things. Others I have found do now appear to be able to handle the draw. I have been going around in circle asking about this, and samsung sent me from pillar to post.
Thank You

What does the switch look like? If you know the brand and model number, that would probably be enough.

There are some options that mechanically will push a button or move or switch without needing to be wired in at all, so some people use those for some pumps and heaters.

Also, what country are you in? The device selection does vary.

hi. I am in the UK. Its a normal switch. Like this I am based in the UK

Thanks. Actually. I think it might be, an MK one. Like this.

OK, then you have two choices.

  1. you can use the Aeotec heavy duty relay which is designed for high load devices. You wire it in line to the circuit feeding the heater.

This is a Z wave plus device which works fine with smartthings. You have to make sure that you get the zwave frequency that exactly matches your hub the way frequency, so assuming that you have a UK model hub, that would be the following:

I’m not 100% sure, but I think it will run locally just as an on/off switch.

  1. alternatively, you can get a little device which acts as a robot finger to just push the button. This is battery operated and moves your existing switch. It’s Bluetooth to its own mini hub which then talks to the cloud by Internet. It has a manufacturer provided integration with smartthings which works quite well. I use a number of these at my own house, and I wrote a review of them for the forum:

2020 Switchbot Review ( robot button pusher), integration through IFTTT or new V3 app

This brand is available in a number of different countries, including the US and the UK.

It will end up being somewhat less expensive than the Aeotec, but it is a cloud-based integration.

Minihub, required for ST integration:

Switchbot button pusher:

Switchbot has the advantage of not requiring any wiring so you don’t have to worry about accidentally disabling any safety features of the device. You’re literally just substituting for the finger pushing the button.

For attaching products of this type, I highly recommend Subaru which is a moldable glue that dries to a rubber like consistency. Removable but not reusable. Really simplifies projects like this. :sunglasses:

Depending on the amps the switch is actually using, you might try;

Aeotec Nano Switch Z-Wave socket and switch; Nano Switch • Aeotec (Up to 15 Amps)
or the
Frient Smart Cable frient Zigbee wireless Smart Cable for home automation (Up to 16 Amps)

Please let us know how you get on.

Unfortunately, the Aeotec 15A specification is only for US 110v systems, and only with resistive loads.

When used on UK systems, it is a lower limit of 10A, and unlikely to suit a high load device like an immersion heater.

All versions are compatible to these voltage levels and max currents:
110/120VAC 50/60Hz (1 phase only)
Resistive Max: 15A
Inductive Max: 5A
Capacitive Max: 3.5A
220-240VAC 50/60Hz (1 phase only)
Resistive Max: 10A
Inductive Max: 5A
Capacitive Max: 3.5A

(This is from the technical specs you can get to from the link on the product page at the Aeotec site.

Nano Switch technical specifications. : Aeotec Help Desk )

This is why the OP would need a heavy duty switch from Aeotec instead.

The Frient is a good find. :sunglasses: It’s much less expensive than the Aeotec, and it does handle a 15 amp load. It’s zigbee, so it will have a shorter range than the Z wave Aeotec: depending on where the device is located it might need an additional repeater, which would add a bit to the cost. The main question is the load required. Many immersion heaters are 20 amp devices, in which case again we’re back to either a heavy duty switch or something to push the button.

Hi Thanks Mr Roberts.
I like the idea of the Aotec solution. It looks more permanent. Will it definately work with smartthings?
Thanks for all you help.

Thank you Andrew. I am not sure how many amps the tank will draw. But pretty sure it is more than 15/16. I appreciate your help though. M

Aeotec who ironically now also make the Smartthings hub also make or sadly perhaps made a Z-Wave switch specifically for controlling the immersion heater used in a hot water tank.


You might be able to find one on eBay.

Another option is sonoff. They do a 15a power switch (POWR2) which will also monitor the power consumption.
Or they do a 16a TH16 which is actually a temp and humidity sensor but you can use it for your purpose and just ignore the temperature reading. They are both available on eBay in the UK and are about £15 each. They both work with Smartthings, alexa and their own app (ewelink).

BUT the first thing you need to do is check your immersion and see what power rating it is and then convert that to amps.
Power (watts) ÷ Volts (240) = Current rating (amps)

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What’s the brand and model of the immersion heater?