Heatmiser WiFi thermostat

I mentioned a while back that I was waiting for a Heatmiser Wifi thermostat to test, and thought it about time I gave an update, though you’ll have to wait a little longer before my full review. I’ve had the thermostat installed for a couple of weeks, though it’s a beta version and I’m just waiting on an updated revision to arrive.

The PRT TS WiFi RF uses a remote switch to control the boiler

To recap, the important thing about the unit I’m testing (besides its WiFi geek factor) is that it needs only two wires to the main thermostat, which makes it a fairly straightforward replacement for a lot of domestic UK thermostats. The version I’m testing is the ‘PRT TS WiFi RF’ and should be available in March; it’s a two part kit made up of the thermosat itself and a remote switch, which is controlled by a separate wireless link.

So, there are two things to wire up, but at least you don’t have to run a new cable all the way to the thermostat location, if you only have a two wire+earth connection at the moment.

The remote switch is a standard UK plug/switch size, so can easily be surface mounted or fitted in a wall box near the boiler. It needs a mains supply – which I’ve taken from the same spur that powers the boiler – and then a switched output goes to the appropriate contacts to turn the boiler (in my case, Vaillant combi) on and off.

DIY horrors

The thermostat itself is a little bigger. The rear part is designed to fit in a standard wall box, but it is actually about an inch larger in each direction, so that there’s sufficient space for the touchscreen. Most thermostats that I’ve seen tend to be surface mounted, so you’ll probably need to drill and fit a back box – if you were to put the thermostat in a surface mount box, it would look decidedly odd.

This is the sort of horror that lurks inside my walls

Fitting the back box for that was one of the more interesting parts of the process; I’ve never drilled into a mains cable before… my flat was a pretty simply done 1980s conversion and almost all the electrical points are surface mounted, with the exception of the light switch next to where the thermostat is mounted. I checked that the wires from that switch ran upwards, away from where I was planning to drill for a new wall box, and started work.

After a while, all the lights went out (thanks to the RCD I installed shortly after buying the flat). And this photo shows the reason. The wire that’s been damaged is actually for the next room – instead of going up the wall in that room, it goes all the way through the brickwork and then up the wall in the hall.

And it’s only a few mm below the surface; the original lathe and plaster walls seem to have been simply covered with wire mesh; the new wiring was held in place on the mesh by nails banged in either side of it – I found the same in the kitchen, with the 30amp feed to the cooker – and then about 5mm of concrete render laid on top of the mesh, with a skim of plaster.

So, a bit of a mess to sort out, but in the end I got there, with a back box installed and all the wiring for the thermostat; the existing twin+earth cable was disconnected from the boiler, and connected to the switched spur to provide a 240 volt feed to the thermostat.

Simple setup

The config tool is available for Mac and Windows, but Linux users should have no problem, either

Before connecting the thermostat to the mains, you need to configure it on your computer. There are Mac and Windows setup programs for this, but Linux users should be ok too; when you connect the thermostat via a USB lead, it simply mounts on the desktop as a drive containing a CONFIG.TXT file, and this file is what’s read and written by the setup utilities. It’s plain text with lines like

KEYMODE=WPA2

GATEWAY=10.0.1.1

so a quick read through and you’ll be able to set the options, even without the config program.

Save the config, unplug the USB cable, and then you just need to snap the front of the thermostat onto the back plate – there’s a simple jumper-style connector that mates the front part with the backplate that’s screwed to the wall box – and you’re pretty much done. The instructions say you need to pair with the remote switch, but my units found each other anyway, so I was all set, and everything worked pretty well right out of the box. There’s an iPhone app – which is due to be revised soon, along with an Android version – and of course the built in web server. The protocol used by the iPhone app is documented, and essentially the same as the serial protocol that the company’s equipment uses, and there are third party tools that work with it. For example, if you head over to http://code.google.com/p/heatmiser-wifi/ you’ll find some scripts that will log your temperature in a MySQL database, and plot graphs on a web page, which I’ve set up too, and work fine with the RF stat.

When I’ve finished reviewing, I’ll talk more about usage, configuring your firewall, and so on, but for now, here’s a screenshot of the current wifi interface.

The HeatMiser wifi interface, running on my home network