Wiring of 2nd Tado thermostat in house
Hi,
some time ago my landlord purchased Tado start kit with additional Tado thermostat for our house. I decided to install only one Tado to start with to see how we get on with it and if it is going to work with the non-Tado controller and boiler and then do the second one.
Our boiler is GlowWorm Energy 18s and main control unit is Horstmann ChannelPlus H37XL with 3 zones(upstairs, downstairs & hot water). Both old thermostats were SunVic TLM2253.
First one I installed was downstairs stat. Removed cover, took a picture of wiring, registered the new Tado and started with installation process. My fist stumble(as someone who has no experience with electricals) was, what I'm I going to do with cables which I don't need. Original SunVic setup had 5 cables(blue, grey, brown, black and green/yellow neutral) but Tado needs only two. I wish I taped on 'Next' in installation process of Tado app where it was explained. It would save me half a day of getting parking 'clips' for unused cables. 🙄 Below are picture of wiring of old thermostat and then Tado wiring.
Anyway, after I figured it out Tado was up and running within 30m. Could not be any simpler. Two weeks later I decided to do the upstairs one and immediately after removing the cover I noticed that colour of cables connected in the old thermostat is different to the one downstairs. Once I removed the backplate of the old thermostat I also found that there are two sets of cables coming from the wall, unlike downstairs where I had only one.
I still followed the instruction on the Tado app and connected them as it suggested, but Tado would not fire up the boiler. I tried various different combinations of brown and grey cables connected in to NO & COM terminals, but without any success. Tado would not start the boiler. I tried to contact Tado CS who first rebooted Tado and then asked me to stick both brown cables to NO terminal(as on pic below) to exclude the Tado fault. They are saying it is boiler fault and I need to get it serviced. But it works normally, with SunVic stat back in place. I also tried the Tado in downstairs dock and it works like a charm.
Can someone help me as to why the heck there are two sets of cables upstairs and which of them goes to NO & COM terminals? Many thanks for any suggestions.
Answers
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Starting here. This link: gives the wiring diagram for the TLM 2253.
Pin 1= Switched Live (NO)
Pin 3= Permanent Live (COM)
Pin 4= Neutral (normally parked)
Methinks the one with double wiring was originally intended to handle a timeswitch nearby, but eventually a decision was taken to remove that and handle it all with a thermostat. Problem is that without having access to a multimeter, one cannot directly trace the source of the original live. Logic suggests that the source will be close to the boiler - as all these thermostats, as they are currently configured, do is turn the power to the boiler, on or off.
Is there a wiring box nearby the boiler which handles the wiring to the pumps, the boiler and the thermostats? You will need to borrow time from someone who knows how to use a multimeter to trace the wires and simplify the circuits enough so that all the risks are removed. It shouldnt take more than 2 hours. If you do have a multimeter, know how do check for closed and open circuits, and have found the central wiring box, this is relatively easy to handle. The key is that central wiring box.
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Hi policywonk,
thanks for your reply. I knew that professional help with upstairs one will be needed! Heating times and all wiring is handled by Horstmann heating hub, I reckon, and this placed right next to the boiler in the utility room(pic below). Did you mean that, when u said "wiring box"?
I would also like to point out that upstairs SunVic utilizes one brown cable from each wire set, both blue ones(downstairs the blue cable was just pushed in the wall) and both neutrals. Grey and black cables from each wiring set are just parked in the wall, not in use. Whereas downstairs both black and grey were connected to SunVic terminals. Does it change anything on your time switch theory?
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