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

Heatmiser mac tool
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


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.

HeatMiser web
The HeatMiser wifi interface, running on my home network

9 Replies to “Heatmiser WiFi thermostat”

  1. Morning,

    I am thinking of getting one of these. My boiler is in the attic so a wireless thermostat is what I need. Would I be correct in saying that the only electrical works would be to install the remote switch with power supply (probably from the same spur as the boiler like you have done) in the attic. and for the thermostat it self all it needs is a wall box and 230 V power supply to it. IE I would not need any kind of wiring from the boiler to the thermostat. (and thereby not need wiring to go through the house)

    What are your general thoughts on usability as well as I currently have a rubbish basic wireless thermostat and anything would be an improvement.

    Looking forward to your response.

    Jeremy MacMull

    1. Yes, that’s correct. No wiring between the two; I happen to be using the old thermostat cable to provide the mains power, but of course that could come from anywhere you like.

  2. Can I pair multiple thermostats to the same switching box – to create a demand when one of several rooms need heat ?

    If so in this mode are the thermostats aware of each other at all – for example to communicate and provide one unified web control page or are they all totally separate ?

    1. I honestly don’t know that, but I’ll see if the guys from Heatmiser can pop over here and answer. They’ve also just opened a forum of their own

  3. Hi, Thanks for the great review, it is good that Heatmiser are allowing you to talk about the product here while it is still a Beta release.

    I am looking for a solution like this for a holiday home but need the addition of hot water control. Heatmiser have a wired device that does that but to avoid rewiring the heating controls to the thermostat location I really need a wireless thermostat and Wifi connected base with HW control.

    Do you know if that may be also under consideration?

  4. Have had the Central Heating and Hot Water version since late 2012, I think that I must have purchased one of the very early models. Very happy with it except that for some reason, every now and again, it freezes and I am unable to make contact with it via 3G. Can still control it at a distance via WiFi, say in a cafe etc. But the 3G not only refuses to work, it canfreeze the stat so that when I get home I have to switch it off and then switch it on again. If anyone has a solution to this, I’d be grateful.

  5. I installed one of these Heatmiser Wifi FT kits in Jan. Generally works Ok, but every now an again the RF bit fails. Just to be clear the WIFI works fine and i can use an ipad to control the thermostat, no problems there, and it works away from home too as long as you get yourself a fixed ip and portforward on your router.

    It’s the wireless comms link between the wifi thermostat (in the hall) and the receiver next to the boiler (in the utility room) that doe has the problems. The rRF receiver contains the relays that actually switch the HW and CH valves, so this is pretty critical. When these lose coms the heating goes into failsafer mode where its on for 12 minutes every hour – not clever when its zero degrees outside ( and the water i thing just stays off). Spent 2 or 3 hours talking and trying to diagnose issue with at least three of the Heatmiser technical team, but not resolved. In the end I have bought a new kit and will return the old one. Guess what when i installed the new one it is worse that the old one. The first one used to lose contact every few days. but this has done it twice in 4 hours. There must be an under-powered comms transmitter and receiver in these units as I previously had a Drayton Digistat +3 RF which had no problems at all with its thermostat and receiver in exactly the same locations. The two units are only about 7m and brick wall apart, which should not phase a wireless coms link

    It’s a shame because this poor RF lets down what is otherwise a well designed product.

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