Immersion heater help

Hi all,

I would like to try and use Smartthings to control my immersion heater but I’m a little confused as to the best way to do it. I currently use a Horstmann timer:

There are two elements, the element that is heated during off peak hours and the one at the top that’s used for a 1 hour boost. I want to be able to control just the off peak element and was hoping to connect the element to this device:

And then in turn connect that to the existing timer. Would this solution work? And more importantly, would the Secure device work with smart things?


Have a read of this:

I have the DH mentioned in this thread. I use it as follows:

I can change the thermostat temp using SmartThings which in turn uses the DH, that then sets the temp on the thermostat (ASR-ZW) which in turn controls the switch (HRT4-ZW).

The question is can you connect the HRT4-ZW directly to ST and then turn it on and off? I’m unsure but I do have a spare one. If no one else has any other ideas I’ll try and have a look for you at the weekend.

Keep your eye on eBay. They sometimes go for next to nothing.

Okay, I had 5 minutes so I had a look.

I took my spare ASR-ZW, added it to ST as a thing and it gets detected and added as a Z-Wave switch by ST.
Using the default device handler and turning the switch on and off does nothing.

A quick search revealed this post which states:

According to their documentation, it uses the Thermostat device classes, so it should work in ST with the default thermostat device handler.

So I went in the IDE and changed the device type to Z-Wave Thermostat. That allowed me (in a roundabout way using one of the thermostat buttons) to turn the ASR-ZW on and off. Which in turn means you could control it with CoRE.

It really needs the default z-wave thermostat DH changing so that this simple on/off device can be controlled.

Suggest you also read this:

Hope that helps!


Thanks so much for your speedy response. So theoretically it does sounds like I might be able to control it as I like. Please excuse my ignorance, however, as I wasn’t quite sure what CoRE referred to.

Thanks again.

CoRE is a rule based engine.

See here for a good intro: CoRE for Dummies (How to get started and make your first Piston)

My thought process as follows:

You really need to modify the device handler (or find someone who will). Using a thermostat device handler to control a z-wave switch is a bit cumbersome, there’s a load of redundant controls (temperature set point for example) and to turn the unit on/off I had to cycle a single button in the device through four press:

  1. Heat (this turned the unit on
  2. Cool (did nothing)
  3. not sure about this one but the device button changed from cool to –
  4. Off (this turned the device off

Using CoRE would allow you to setup some simple logic to turn the unit on/off at certain times or based on some other inout (motion). It would also allow you to apply other logic such as don’t heat when I set the mode to Away. Depending on your use case this may sufficient.

@ajayb21 here you go. Tested and looking good.

Think I better go and get some stuff om my own to do list now :slight_smile:

Wow, what a legend! Thank you so much :slight_smile:

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No problem at all, you may want to remove that personal info!

Roger that! I’m off to order an ASR-ZW now :slight_smile:

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This is an underrated device for the money. It’s a Z-Wave repeater. Dry contact relay. It really could be used for a number of things.

Let us know how you get on!