Installing a tado Smart Thermostat - easy but yet difficult - looking positive and already helping

  • 2 October 2021
  • 28 replies

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28 replies

Userlevel 7
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Three cables feeding into a central-heating control point is quite common @Tim_OVO.

There is one to supply the electricity needed by the thermostat/time-clock itself.

The second cable connects back to the boiler with a ‘switched live’, telling it when to operate.

Cable number three goes to the 3-port valve which directs boiler output either to radiators or a DHW cylinder. That’s usually a 3-wire plus earth cable, but can be 4- or-5-wire if the controller receives feedback from the motorised valve.

Moreover, if the house had been through a couple of previous boiler or time-clock replacements in its time, then those cables could be a rich assortment of wiring colours! :scream:

A ‘black’ wire could be a neutral or a live control-signal to the 3-port valve.


And at this point you begin to realise that a cut-price offer on a wonderful new ‘wireless’ smart thermostat might result in some considerable time being spent by a qualified electrician or heating-engineer to install the receiver end. All this costs money.


Here’s an example of a YY Control-cable connecting to a box on my own Thermal-store. It’s got 5 internal wires, including two blacks. I’ve labelled it so you can see what each does:


This is definitely the ‘right’ way to connect this box to the manifold control unit on the next floor-level. But many installers wouldn’t carry such an exotic cable.

Instead they’ll use the common mains cables for lighting circuits (1.5mm²) and label the conductors at each end (hopefully!).

If a cable doesn’t have enough cores, they’ll simply run another cable alongside it.

Userlevel 7

A really insightful walkthrough of your experience, @EverythingNeedsAUserName - great post!


From your experience some of the advice in that instruction manual and parts of that journey (such as your web chat /  bot experience) sound like they need optimising. I’ll share this with the OVO team that are working on Tado related insights - they may be in a position to share this with Tado directly. 


Love the screenshots, this topic is available and ready to help members who may be on the look out for real people’s experiences, at any and all stages of the installation process. 


I’d like to try and get more info on this wiring. I’m comfortable to admit that I wouldn’t be confident myself when dealing with unexpected wires that don’t follow what the installations describe. @EverythingNeedsAUserName or @Transparent can you help novices like me understand why there would be so many ‘mains control cables’. 3 cables splitting into 10 wires. 


Where to start with this? When is it best to get an electrician? @PeterR1947 would appreciate your advice here), what risks of things like an electrical shock are there? 

Userlevel 7
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Great narrative @EverythingNeedsAUserName 

Frankly I think this Forum can do better at support than any chat-bot or manual. Let’s see what help we can put together between us.


I’m going to kick off by suggesting multi-core mains control cables (class YY) which can link the boiler to the Tado receiver:

7-core YY mains cable at £1.56/mtr +VAT and 5-core heat-resistant at 64p/mtr +VAT from TLC-Direct

7-core YY control cable

With YY control-cable you get an earth and all the other cores are black. Label them with PVC tape as you proceed. YY-cable may only be used for control signals. It is not certified to carry power to an appliance even tho’ it’s mains-rated.

Screwfix also do a 10m coil of cable type 3095Y (5-core) at £7.52 incl VAT. This has coloured cores. The equivalent from Toolstation costs £8.87. Cable type 3095Y is mains-rated and heat-resistant. It’s normally used for temperature controls close to hot-water cylinders.


If you’re trying to fit a Tado receiver in a position where there was a originally space for a 2-gang control box, I suggest you get a PVC blanking plate. Bolt the Tado receiver to it in the centre, leaving the two screwholes at the ends for the M3.5 bolts to secure onto the existing patrass-box.

PVC faceplates are thin and can be drilled without shattering. Toolstation have them for 59p each. But ignore their photo. It actually looks likes this:

PVC 2-gang faceplate

If you don’t feel able to bolt the Tado receiver to the blanking plate, double-sided tape would probably suffice. Either way the receiver will cover up whatever size hole you’ve made for the cable to pass through. :slight_smile: