Installing Netatmo on a Worcester 38CDi Greenstar Boiler


We are at the forefront of home automation through the internet of things.  It’s a great time to be a programmer, since we have some unique challenges to overcome.  I looked around at a few smart thermostats, I was really impressed with Nest, it feels like a quality product.  Sadly they do not support Apple HomeKit and since the majority of my devices are made by Apple, it’s not an option for me.  Sure I can go down the Homebridge route, although why bother when there are some good products out there.

This post will show you how to install a smart thermostat, step-by-step with the use of images.

The only two current smart thermostats are the Netatmo and Honeywell that work with HomeKit.  I managed to pick up the Netatmo for £104 which I found to be very reasonable.  Their website also suggests smart radiator valves would be coming soon; something that would complete smart heating in my home.

How do thermostats work?

They work by either switching your heating system on or off depending on the current ambient temperature where the thermostat is placed.  That’s it.  I have heard friends complaining they are cold and setting a thermostat to 30 degrees in the hope it heats up faster.  It won’t, just like an oven wouldn’t.  When the ambient temperature reaches the target temperature, it simply turns the boiler off.  If it drops below the target, it turns the boiler on.


Disclaimer: I take absolutely no responsibility for any issues you face and am only documenting my own experiences, use this entirely at your own risk.

You’ll find the Netatmo and probably most others will have two 2-core cables.  One is the power to the device, through live and neutral.  The other is the switch, which is most often not polarised (meaning it doesn’t matter which way around the wires go).

  1. Ensure power is completely disconnected before you begin (cut it at the fuse box) and ensure it’s completely dead before starting.
  2. Remove the outer case.  There is a clip at the top in the middle and two screws at the bottom.  You do not have to unscrew the bottom screws all the way, just enough to get it over the ‘lump’.  When the screws are loose and the top is un-clipped, pull the case towards you and it will come off in one large piece.
    Boiler with the outer case still on.

    One of the screws you need to loosen (the other is in the same place on the other side)
  3. Now the case is off, you will want to disconnect your existing thermostat if you have one.  My boiler uses the DT10RF Worcester Digistat Optimiser, which has a wireless RF thermostat and a module plugged into the front of the boiler.  Unscrew and remove the plastic cover just above the module.
    Existing RF thermostat module in the middle.  Screw at the top, left of that.

    When the screw has been removed, pull up the tap that’s just right of the center of the thermostat with an up arrow.  This will detach the module.  Unplug the ribbon cable.  I don’t have a blanking plate to replace it, so I taped mine up to ensure it doesn’t short anything and re-fitted it, disconnected.

    Disconnected and taped thermostatic module.
  4. Now the thermostat module is disconnected, we can fit our new one.  The front panel of the boiler folds down.  You need to slide the plastic clip down, and gently pull the front down.  It should rest there on its own.

    Boiler with the front panel pulled down.
  5. Remove the plastic cover with the electricity warning symbol on it.  There are three screws to remove that, one at the front and two at the back on the left and right, just next to the wires going into the section.  Try and pull the panel straight up, it may require a bit of wriggling, but it’s easier to get back on.

    Electricity cover panel lifted off, exposing the main board and electrics.
  6. Pass the two wires through the bottom of your boiler, ensuring it wont snag on anything when the panel is lifted back up.  Cut the top off of two of the cable clamps (I used a sharp knife) and loosen the black screw in the middle.  Feed the wires through the top of connector blocks:

    Wire clamps for securing your new thermostat wires.
  7. Locate the green connector block on the left hand side towards the back.  This is where the power to your boiler is connected.  It is also where you will connect the thermostat.  To make it easier to see what you are doing, the connector block easily detaches by gently pulling it upwards and off the board.  You will see the brown wire (live) and blue wire (neutral) going into the connector block (labelled L and N respectfully).  Connect the Netatmo brown and blue wires to the same terminal as the ones already there.  At the other end of the connector block, you will see a small jumper between two of the terminals (between LR and Ls).  This needs to come out and the Netatmo switch wires (grey and black) need to be connected here (either way around).

    Main connector block for power and thermostat switch wires.
  8. Push the connector block back onto the board and ensure the wires are neat and tidy.  Pull any excess through the clamps and tighten the black plastic screw to clamp the wires in place securely.
  9. Mount the new thermostat somewhere, ideally out-of-the-way of anything that could hinder the wireless signal.
  10. Put it all back together again, doing the reverse of what you have done.  Your thermostat is now fitted.  Download the app and set the device up!

Can’t find the HomeKit code?  Usually it’s on the box, although not for the Netatmo.  In this case you need to press the small home icon in the app (bottom left of the thermostat picture).  This then causes the thermostat display to show the HomeKit code.


A relatively simple job, although it can be daunting if there is no guidance out there (I couldn’t find any for my boiler).

Now that it’s all up and running, I would highly recommend signing up to If This Then That.  I have a few applets setup, one that switches off the heating if the outside temperature is over 18 degrees.  I have another that sends me notifications whenever the thermostat is manually overridden.  You can tie them into all kinds of things, the possibilities are endless.

You might notice if you try to control your HomeKit device whilst not connected to your local WiFi you won’t be able too.  You need an always connected Apple TV or IPad to allow you to use HomeKit when away from the home or on another network (such as 4G).  Luckily I have the Apple TV and the entire system works flawlessly.


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