Drayton Digisat SCR wiring question


The wiring on my existing Digisat SCR is slightly different to what the Tado app is suggesting. I’ve emailed support, but not expecting an answer on a Saturday, so hoping someone will be able to direct me here.

The in-app instructions say I need to label up the wire in terminal 2, but on my setup there is no wire there, but there is one in terminal 1. Should I connect this wire to CH COM or CH NC on the tado receiver (I think equivalent to 1 and 2 on the Digisat)?

I can’t see a way to post a photo here, but if I can I will add that…


  • You can post photos if you use the desktop version of the forum. Do you have a combi or system boiler and what Tado device are you trying to wire in?
  • Thanks so much for your response. It is a combi - a Vaillant ecoTEC plus 832 - and the tado Wireless Smart Thermostat Starter Kit. I still can't see how to post a phot from the desktop... Will investigate further...
  • Oh, it's that easy!!
  • In case I was confusing - I meant attaching pictures is that easy. I still need help with the wiring query, please!

  • Do you have a single zone heating system? That wiring doesn’t look like what I’d expect for a combi.
  • We do have just one zone. What looks unusual to you? And how would it normally look?
  • Just to say: the person who lived here before us made some strange choices around electrical wiring, many of which we have had repaired and replaced since we moved in
  • The standard Tado wiring for a combi is in the manual below. I think yours is wired to switched live. I would try that first. You might need to open up the boiler and see how it’s wired in there (you should be gas safe or use someone who is to do this).

  • So would trying it as you say mean connecting what is currently going to 1 to CH COM? I am most certainly not Gas Safe and only partially competent at the best of times!
  • johnnyp78
    johnnyp78 ✭✭✭
    edited December 2022
    Try n - n, l - l, 1 - Com, 3 - NO

    If that doesn’t work, try n and l as before, bridge l - com (park the black wire), 3 - NO.
  • So L and 1 are bridged in the original setup, and you’re saying not to recreate that in the first option, and if that doesn’t work then do bridge them, as in your second option, right?
  • Or try bridged first. There’s also a com wire as well as a bridge, which is what I don’t understand.
  • I've wired that as you suggest, which makes sense to me as it mirrors the original wiring. Complete rookie question follows: you'll see from the attached photo that the earth wires don't reach the earth terminal. I think I read somewhere else on here that they are not necessary with this setup. If that is so, how best to make them safe? Thanks so much for your help with this.

  • I’m not an electrician but I would attach the ground terminal if you can. Can you cut some of the casing back to let the earth wires reach the ground terminal?
  • I got the two Earth wires connected, and the receiver is working now, but the boiler has no power. Could that be caused by bridging L and CH COM? Should I remove that bridge and see what happens?

  • johnnyp78
    johnnyp78 ✭✭✭
    edited December 2022
    That explains the additional wires - it looks like the power was run through the thermostat to the boiler, which as far as I’m aware is unsafe at the very least if not illegal. I think you need to get an electrician in to sort this. I wouldn’t try imitating the wiring through the tado wireless receiver either.

    Where did that other wire go to that was wired into the original thermostat?
  • If @GrilledCheese2 is around he might be able to shed some light on this.
  • Can certainly confirm it appears the power was run through the thermostat. Darn, I thought this would be easier, but hadn’t taken account of how things were set up to start.