Help with wiring the hot water controler

Hello, I have just bought a Tado Starter Kit V3+ (in programmer with hot water control) Following

and reading the set up instructions (but not yet physically fitting the Tado devices) they are very easy to follow, both for the Bridge and the Wall Thermostat, however the programmer isn’t as clear to me.

Details and Background

I have a Potterton Pro Max SL, with is currently controlled by a Dual Channel British Gas Programmer, a wired thermostat Thermostat in the hall, and very complex Salus box full of wires!

The back plate of the British Gas Programmer looks quite simple. 

Blue wire into N

Brown wire L

Yellow and green wire into 1

Black wire into 3

Grew wire into 4

A spare black wire has been taped off

The Salus box of wires is very complicated so I’ve not attempted to describe them here, but I hope I don’t need to touch this and instead just connect the programmer where the old one used to be!



  • Anyone able to help? Was really hoping to install this weekend.

  • Just to clarify, have you bought the wireless starter kit? Is your boiler a combi or system boiler? Is your house multizoned?
  • Thanks. My house has got the boiler on the ground floor in the kitchen, a hot water cylinder on the first floor in the airing cupboar, and a cold water tank in the loft. I bought the starter kit V3+ wireless smart thermostat including programmer with hot water. The house is not multizoned.

  • Sounds like a gravity fed system. In theory it should be a fairly simple install if you just have either an s or y plan system. There may also be an external pump.

    Looks like you might have an s plan system. Have you received customised install instructions from Tado? There are generic ones here but it’s better to see what they say.
  • I think it's an externally pumped gravity fed system. It's pretty old, 10 years plus. No idea if it's an S or Y system. Here are a couple more pictures.

  • @GrilledCheese2 @wateroakley @starconf any ideas?
  • Looks like a fully pumped Y-Plan setup. Transfer the wires as labelled below. Leave the insulated black wire alone and no need to make changes to the wiring centre.

  • Fantastic, thanks for that. Do I also need to add the purple bridging wires?

  • Yes, you will need to add the purple wires to connect Live to both common terminals.

  • Looks like a Y-plan to me. Grilledcheese has it sussed.

  • Ok, so I thought i'd installed it all correctly this afternoon but then turned on the heating this afternoon and... the boilers not turning on! I've tried turning both the wireless themostat to 25c and then a tado room trv to 25c and neither are turning the boiler on.

    As I installed the programmer as per grilledcheese2's diagram i'm wondering if i've done something wrong with the wireless thermostat in the hall. I had a basic dial thermostat with brown, blue and yellow/green wires. I've capped these off individually as per the instructions but wondering whether i've misundersood something or whether I needed to have in fact bought a wired thermostat system (the tado website said I needed the wireless one as I had a hot water tank).

    The other bit I wonder if i've got wrong is the configeration step 6. Following this step I get a green light (s-pland and y-plan fully pumped) but am wondering whether I actually need a blue light (gravity fed) as I have a header tank in the loft, but I couldn't get the light to go blue.

  • GrilledCheese2
    GrilledCheese2 ✭✭✭
    edited October 2022

    You need to connect two of the wires from the old thermostat together (bridging) for the system to work. One of those wires is Live, I assume it's brown. And one of those wires is the Switched Live. The wireless receiver is now doing the switching but you need two of the old wires permanently connected to make the circuit. Normally the blue and yellow/green wires are Neutral and Earth, but I assume one of them is actually the switched live. There really should be a brown sleeve to indicate the original wiring colour is no longer valid. Do you have a photo of the old thermostat wiring? You don't want to get this wrong, because it will make a bang and potentially damage your wiring.

  • Thanks, I thought that might be the case as I thought I may need to connect, but the colours didn't corresond to the tado instructions so thought it best to cap individually for the reasons you said.

    I did take a picture of sorts. Unfortunately the wires were very sort and the box wouldn't come away from the wall without undoing the wire screws but this is how they looked one removed. Looks like brown in 1, yellow in 3 and blue in 2.

  • Forgot to add the picture!

  • I was hoping for a picture of the wires connected to the screw terminals.

  • Those are the screw terminals on the left of the box. They went into the numbered holes and the screws are on the other side. I removed being carefull to keep the wires in the same order and width appart so I could see where they went. The brown was in the screw terminal 1, yellow in 3 and blue in 2.

  • This is the picture of the other side.

  • Your Salus wiring centre "appears" to be wired according to the default wiring instructions. This means terminals 2 and 3 are used for the thermostat. I can see the yellow/green wire is connected to terminal 2, which means it is likely to be the switched live. So you need to connect the brown wire to the yellow/green wire for the old thermostat. Keep the blue wire separate. Before you do this can you check the individual wires on terminals 2 and 3 of the wiring centre go back to the same cable.

  • Thanks. Zooming in on the pic it looks like they do but i'll take a proper look in the morning when it's light again as I like to turn off the who circuit board to be on the safe side. Thanks again.

  • Just thinking, if there's any doubt is there an easy way to test? My dads a retired electrician and coming to visit tomorrow (to help me run power to my shed). He's been retired for several years but still has all his gear to test if it's straight forward to do.

  • Yes, it's easy for an electrician to check. In the Salus wiring centre the 4-way connector block on the right is the Earthing terminal. There should be no continuity between these Earth terminals and the wire on terminal 2.

  • Fantastic, thank you, you're help really is appreciated!

  • Hello again. Can I just check, should I have a green or blue light on my system?
  • I've now tried it with both and neither seem to get my boiler to respond. Not sure what's gone wrong. Last night my boiler would turn on for hot water, just not heating. Any ideas?
  • Just checked the boiler. There does no appear to be a pilot light. I tried ressetting but it doesn't appear to do anything.
  • Not quite sure what happened but after a couple of hours tado and the boiler seemed to kick in and from what I can tell it's now working as it should :) I'll see how it goes for the next few days. Thanks again.
  • Good to hear you got the system working. Not sure why you initially had a problem, but hopefully no more issues.

  • Hi GrilledCheese2, unfortunately its proving very tempramental. I noticed a few minutes ago when I cranked up the thermostats to try and get the radiators to turn on (the app was saying the rooms were heating but the radiators were cold) that the wireless controller had a snowflake and arrow on it which I think means it was downloading.

    I think this may all have something to do with the initial set up and whether I should have a green, blue or orange light. Are you able to confirm whether my system is fully pumped or gravity fed.

  • I went for the gravity fed. If that's the wrong choice I can try the other again but it didn't seem to work the last time. I wondering whether it's the wiring of the thermostat as the hot water still works.
  • The snowflake and arrow means your system is downloading a new configuration, not firmware. Perhaps the system is being slow to respond to changes that you are making to the setup.

    Your system is definitely fully pumped and definitely Y-plan. I see your pump in the original photos is pumping downwards into the 3 port valve. In the valve is a diverter that directs the water to either the HW or CH outlet. Or the valve can be mid-position where water is pumped to both outlets at the same time.

    If a Y-Plan system is mis-wired or the 3 port valve fails it can lead to some explained behaviour. The valve position is determined by the voltage on the control wires.

    You can check the pump is working for both HW and CH by feeling/hearing the motor running. By feeling the left and right outlets on the valve you should also be able to determine which direction the hot water is flowing.

    This link gives a pretty good explanation about how your heating system works.