Tado and Drayton LP722

[TeamTayLoc]

Hi!

I have just replaced an ancient thermostat with a Tado smart thermostat. I always assumed that the old thermostat didn't work, but actually I think the issue was the way it was wired! The tado thermostat is completely ignored by the boiler and the boiler is on all of the time.

Please see the attached images which show the wiring in the thermostat and inside of the LP722 programmer. As you can see, it looks like the yellow wire that is connected to Tado actually doesn't terminate inside of the programmer at all!



I have two questions that it would be awesome if you can help me with

1) If the thermostat is effectively disconnect, why does the boiler run?

2) How should the thermostat be wired from the programmer? My assumption is that COM inside of tado should be connected to L in the LP722 and NO inside of Tado should be connected 4.

Is anybody able to confirm?

Many thanks in advance

Andrew

 

[stem]

I have two questions that it would be awesome if you can help me with

1) If the thermostat is effectively disconnect, why does the boiler run?

The thermostat is a simple switch 'on' or 'off'. From an electrical point of view that's all it does. The programmer can be wired to the boiler directly instead of via a thermostat so that it will switch the boiler on and off according to the preset time control only.

2) How should the thermostat be wired from the programmer? My assumption is that COM inside of tado should be connected to L in the LP722 and NO inside of Tado should be connected 4.

You are on the right lines, but not quite there. What you propose would mean that the programmer would still be overriding the Tado, and switching the heating 'on' based solely on time. The 'Com' of the Tado should be connected to 'L' of the LP722 (CH On) as you say, but the red wire should be removed from terminal 4 of the LP722 and connected to NO of the Tado, meaning that there will no longer be a wire connected to terminal 4 of the LP722. That way the LP722 will no longer have any control of the heating and the Tado will take sole control of it.

 

[Gaz the Sparky]

I would get an electrician in to fit the Tado for you!!!

You honestly don’t seem to understand how a thermostat works and wired

The yellow wire is in fact connected to the boiler / wiring centre

As you currently have it you have connected the Tado up completely wrong and connected a neutral cable to a live cable through the Tado thermostat

This may seem harsh but for your own safety and so not blowing the electrics in your boiler or expensive Tado

 

[stem]

I would get an electrician in to fit the Tado for you!!!

A good suggestion and in hindsight, probably one that I should have made. When it comes to wiring you do need to have a basic understanding of the circuit in question and how it works.