Boiler wont turn off when all SRTs are off

woolcer

Hello wonder if anyone can help.

I have the tado wired system (thermostat, bridging thingy, and 9 out of 10 radiators are fitted with the smart radiators.) I have a Vaillant ecotec plus combi boiler.

When I turn all the smart radiators off the remaining non-smart radiator is on full blast and it looks like the boiler is on as well.

Now how to turn off the boiler and stop the non-smart radiator heating up? At what temperature on what thermostat will the boiler stop heating the non-smart radiator if all the smart ones are turned off (down to 0)?

I have turned right down to 0 the non-smart radiator manually and the boiler is still firing, what exactly is it heating?

Lots of questions, thanks for any information you can provide.

eezytiger

Your setup sounds exactly like mine, except that my boiler only fires up when one (or more) of the SRTs, or the Smart Wired Thermostat itself, requests heat.

I don't have an answer I'm afraid. You could try rebooting the Smart Wired Thermostat and/or the Bridge. You could try unclipping and refitting the Smart Wired Thermostat from the back plate. Beyond that I'm clueless. Question though - did it ever work correctly or has it always been like this? Could it be a problem with the wiring to the boiler? Are you using relay switching or e-Bus?

woolcer

Thanks for the comment. I don't have a Tado receiver wired directly to the boiler, it is the original Vaillant receiver that is wired into the boiler. Ive just bought it and installed it.

The idea was to just have the seperate thermostat so as not to have to monkey around with the electronics in the boiler. Looks like I will have to do some monkeying anyway!

How do I know if the (Vaillant) receiver is relay switching or e-bus? And what should it be?

Thanks.

eezytiger

If you don't have the Tado Smart Wired Thermostat connected to the boiler then what is it doing? Tado can't control the boiler if there is no connection between the two. Or did I misunderstand your setup?

When I installed my Tado system I removed the existing timer/thermostat and physically replaced it with the Tado Smart Wired Thermostat, using the existing wiring. In my situation the existing wiring was for relay operation, so I continued with that.

The installation instructions explained what needed to be done to switch them over.

This is my old timer/thermostat. There are just two wires that needed to be disconnected here and reconnected inside the Tado thermostat once I'd completely removed the old unit. Note that for relay switching the wires carry mains voltage, so turn off the supply to the boiler before you go messing with wires.

woolcer

Thanks, so where do the two wires from the current Vaillant box go in the Tado thermostat? this is the back of the Tado thermostat.

eezytiger

The wires to be connected depend on whether the existing installation uses relay switching or e-Bus. I'm not a heating engineer and I don't know what options your existing system has so I have no way to tell which is correct. Hopefully you can tell by looking at the existing connections.

For instructions go to the Tado app and in Rooms and Devices click the Smart Thermostat. Then click Installation Instructions and provide your current details. You should then be led step by step through the wiring process.

woolcer

I am pretty sure it is e-Bus as that is what the current system is labelled as where the two worries go into the box. I have sent a mail to the support at Tado before I continue though. Just want to make sure I follow any instructions. The boiler I have isn't supported in the automatic installation process through the app, in fact almost none of the Vaillant boilers are.

Thanks for your help anyway.

eezytiger

That's odd. I have a Vaillant Ecotec 831 Plus and the instructions were provided for my Drayton relay controller.

Maybe it was a simple process for me because the old Drayton controller only supported relay switching.

E-Bus can make things more complicated because, apparently, not all Vaillant boilers will talk e-Bus with Tado. Mine actually does, and I have swapped operation from relay to e-Bus (and back again). It definitely worked with e-Bus, but did not appear to be operating efficiently, so I switched back to relay mode again.

woolcer

Thats odd, I ran the installation process again and searched for your boiler and it came back saying that it wasn't supported in the step by step process.

Screenshot 2021-12-30 at 10.32.58 (002).png

eezytiger

What they are saying is that the expect you to *replace an existing timer/thermostat* with the Tado Smart Wired Thermostat, using the existing wiring.

That means there should be no need to open the boiler and start changing wiring inside the boiler.

So, yes, they don't instruct you to wire the Tado to the boiler. That wiring is already in place. You just need to switch the existing wiring between the two thermostats. In my case I switched my Drayton timer and used the two existing wires without touching the boiler at all - at least using like for like relay switching.

To convert from relay to e-Bus and back again did need the internal boiler wiring to be changed each time.

woolcer

Thanks,

To be honest, is trhere any need for a Smart thermostat? Couldnt you run the whole thing through the individual smart radiator valves? Ive got 9 smart valves on 10 radiators, they can all call for how water individuallyt cant they? Why do we need the smart radiator?

woolcer

Why do we need the smart radiator thermostat? I meant.

eezytiger

Something must be there to turn the boiler on when needed and off when it isn't. The smart thermostat is the magic that connects between the valves and the boiler so that they communicate this need.

If you use a non smart thermostat to control the boiler then the valves on the rads can open and close to a timed schedule, but they can't ask the boiler for heat and tell it to shut down when none is needed. You need something else to control the boiler on/off.

You can use your original timer/thermostat, but it loses the smart sophistication of heating exactly when needed in each room. Sure, the radiator valves are real clever, but you're still left with a non smart boiler that only works when the room with that dumb thermostat wants heat. The rest of the house can only get heat when the master thermostat also wants heat.