V3 Wireless Receiver Installation

Yes, you've got it right. Obviously you connect the Live and Neutral too.

It's possible there's a problem with the receiver, but it would be unusual. Have you tried connecting just the Live and Neutral to the receiver, leaving off CH NO and HW NO. If the fuse still blows, then it would suggest a faulty device.

I’m no spark, but from recollection, doesn’t a blown fuse indicate you’re mixing L and N somewhere?

It’s not easy to tell from the photo of the existing wiring, but my guess is there’s a crossover there somewhere, effectively with a ‘switched neutral’ (as something has been wired the other way around - not by you, but in the existing wiring).

Try connecting just one of the CH or HW at a time to try to narrow it down. That blue looks favourite to me. (Blue for L??)

Take care though - no NHS at the moment!!

Good call @GrilledCheese2 - that looks like the issue @MrPacE.

The problem with these ago connectors is they bridge if you put in side by side, whereas most of us are use to the end to end connectors here in the UK.

What you may then find, is you have a constant call for CH. If so, put all 3 in separate connectors

Just to be clear, that’s yours @GrilledCheese2

Enjoy your heated home over Xmas, @MrPacE

Right, let's take a step back.

The wiring to the old stat should be L (Red), N (Blue) and SL (Yellow), so 2 in, and 1 out.

If you connect L and SL, you will definitely create the circuit that will switch on the CH permanently, overriding your tado stat.

If you terminate them all individually, you are merely taking the current stat circuit out of the equation (although it does still carry current, which is why it needs terminating). If the receiver is wired in properly, that should not affect performance, as the stat speaks to the receiver wirelessly.

What's happening now though, is there is no CH connection between the wireless receiver and the boiler. (You get the CH light because the wireless stat is talking to the receiver). Which suggests the wire you're connecting into CH NO is not actually the SL to take the CH fire to the boiler (which is odd, if it was working before).

Very hard to tell what's what from the photo of the current programmer wiring. There's a lot in there.

Where are you at now?

Yep, you've bridged it and your tado stat isn't dong anything.

To get the stat working, you need to (2) terminate this old stat wires individually to break the CH circuit there; and (2) create the CH circuit only when the relay switches on at the receiver (CH NO triggered by the stat, wirelessly).

You have N and L into the receiver, per the old programmer. You need to find the correct wire back out from there to continue the CH circuit (if it's not that blue, apparently coming out from the old programmer).

I can't see what you've got there. What's happening with those connectors behind the programmer backplate? Any chance you can take the backplate off and move things out for a clearer view (no need to disconnect anything, but take a photo before, if you do)?

Also, what's your system set up? Do you have a water cylinder, valves, pump, wiring, etc. in an airing cupboard, for instance, or is the programmer wired into a combi?

Ok, we're probably causing some confusion here now, so maybe try what @GrilledCheese2 suggests first, as there's no wiring changes needed. If that doesn't work, we'll have to take another look.

(I'm guessing my wiring might not be S plan after all as it doesn't work as you've indicated. I do have a particularly 'creative' ex-Viessmann engineer though, so who knows what I have. He likes to make himself indispensable!)

Right, so @GrilledCheese2 diagram got me thinking about my wiring set up and I figured out the bridging.

Below is a full S plan diagram. It's slightly different to the sketch above in that it's programmer to room stat but the principle is the same - both on to fire.

As I've had tado in for 10 years, I'd forgotten that the set up back then was basically a combined stat and programmer unit wired in where the old stat was located (e.g. hallway), with an optional remote temp sensor. So applying that below, imagine the programmer is the stat and programmer 4 goes straight to wiring centre 5, with there being no room stat at all. In that set up (mine), bridging the stat wires (where the programmer is located) actually bridged the relay.

However, in your case @MrPacE, you are simply replacing the programmer with the receiver. So, @GrilledCheese2 is right, you should need to bridge the old stat wiring. Otherwise, the SL never reaches 5 in the wiring centre, so never opens the CH valve triggering the boiler to fire.

So assuming (logically) that you can reuse the existing wire out from programmer 4 (which we think is blue), then as @GrilledCheese2 says, it's possibly not a wiring issue. It could be any of the things Grilled mentions above, or it could be the tado learning (less likely) or even that the CH relay is stuck, in which case, when the light it on, give the receiver a couple of gentle taps. Plenty of people on here have found that miraculously fixes everything.

On the tado app, do you have ANY wavy lines next to current temp?

If not, is the boiler running, or has it switched off?

If it's running, is the hot water off?

Do you have any other controllers (e.g. tado radiator stats)?

If you turn the target temp above current temp, does the boiler fire?

So the boiler is apparently off but you have a single hot radiator?

If you've turned down/off all the manual TRVs and any of the rads are still getting heat (e.g. living room), that suggests the relevant TRV(s) is stuck open. Remove the head and push down on the pin on the valve. It should move up and down. Quite common for them to stick. Replace head and see if rad then cools down. If not, TRV possibly knackered.

As for the boiler, next step is to confirm whether or not there's a constant call for heat.

Check what happens at the receiver, boiler and pump when you turn CH and HW on/off. You may need to crank up target heating temp for tado to go full on. Your pump may also overrun the boiler to dissipate heat, so there may be a few minutes delay after switch off.

For reasons discussed above, the old stat wiring is probably now correct, and as far as we've been able to tell so far, so is the receiver wiring (that pesky blue). Other causes of a constant call could be a sticking relay in the receiver, or a stuck CH valve.

Confirm on/off reaction first, then let's take it from there.