Changing over from Danfoss to Tado
I have a Worcester green star AR 24i boiler, CH and HW with a hot water tank upstairs
My current Danfoss system is a CP715 Si controller in utility room and a wired RMT 230 thermostat in the hallway.
I purchased the V3+ wireless starter kit
I disconnected the wired Danfoss thermostat in the hall way.
I then removed the Danfoss controller in the Utility room and wired in the Tado controller as per attached picture, set up internet, wireless thermostat etc, followed the instructions by the letter.
Hot water worked fine but the heating didn’t come on, the app on my phone showed the heating was on but obviously no signal had been sent to the boiler to come on, I put the tado thermostat temp up and also tried boosting heating but boiler didn’t react,
I’ve rewired back in my Danfoss system and everything working as it should again.
Tado telling me I have the correct system supplied by them but should I have had the wired thermostat or what was my mistake. I’m not an electrician by the way
Best Answer
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Do you have access to a mains testing screw driver?
Some notes.
1. According to Danfoss instructions, when there is a call for heat coming from the thermostat, it bridges Pin 1 to Pin 3 on the thermostat. When it needs to cool down it bridges pin 1 to pin 2 instead.
2. This is the wiring for your controller:https://assets.danfoss.com/documents/latest/27090/AN000086407426en-GB0101.pdf. According to this, Pin 4 goes live when heating is requested. Pin 3 goes live when hot water is requested. On the basis of this and your drawing the controller is wired in correctly.
3. Please try this. Leave the danfoss thermostat in place and replace the controller with the tado one. Force heating on, at the tado controller, then turn up the danfoss stat. It should fire the boiler. If that happens it means that the boiler gets is CH call for heat from the thermostat, not the controller.
4. Is that doesn't happen please come back here. If it does - is there a wiring centre between the controller and the boiler? I suspect it takes the live feed from the controller and then allows the thermostat to actually decide whether heat should be called. Could you document the wiring centre? The solution is in there.1
Answers
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Thank you very much for that very informative reply, I haven’t followed your instructions yet encase I blow a fuse in the boiler and left with no heating (North East Scotland) I have fuses on order (none in the boiler spares cover) So all the below information is gathered using the old Danfoss system
I have attached two photos of the JB between controller and boiler and a photo of the wired thermostat
I have gathered this additional information as there are two sets of cables with the same colour cores going into the central JB as the wiring in the wired thermostat (grey, brown, black, earth) the earth has been cut back and is not used in the Danfoss wired thermostat
First cable- Grey into terminal 3, Brown into terminal 5, this has a link into terminal 6, black into the central horizontal terminals, earth into central horizontal terminals
Second cable- Grey into terminal 10, Brown into terminal 9, black and Earth same as above
With the heating system on standby, nothing being asked for and using a meter:
Terminal 3 = 0, T5 = 240, T6 = 240
Terminal 10 = 0, T9 = 0
With heating system on and wired thermostat set at 30 degrees
Terminal 3 = 0, T5 = 240, T6 = 240
Terminal 10 = 240, T9 = 240
With the heating system on and wired thermostat set at 5 degrees (thermostat controlling on/off of boiler, house currently around 17 degrees)
Terminal 3 = 0, T5 = 240, T6 = 240
Terminal 10 = 0, T9 = 240
Thanks again for your assistance
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@davsmith. Going through those photos.
A) Terms 1, 2, 13, 14, 15, 16 have been dropped into the lower chocolate strip.
B) The call for central heating heat comes onto term 9.
C) The wires that go to Terms 9 and 10 come from the programmer.
D) The wires that go to Terms 3, 5 come from your thermostat. I believe the black wire is neutral.
E) Have just found another wiring diagram on the Internet. It now seems that, for the photographed Danfoss thermostat, *pin 2* calls for heat not pin 3. Please check with your multimeter that when set to 30, that both pin 1 and pin 2 go live in the thermostat. I also believe that pin 4 is neutral.
F) If this is correct, then try this.
1. Disconnect term 3 at the wiring centre and insulate it. Disconnect the brown wire that goes into term 5 and insulate it too.
2) Fit a wired link between term 3 and term 5 yourself. This should bypass your Danfoss thermostat forcing a permanent call for heat - and then pin 9 should read 240volts. If that's wrong reverse the wiring back to original and come back.
3) If this holds, you can now fit the tado controller, it should call for heat by itself and your tado wireless stat should stop it calling for heat if you dial it down.
Does this make sense?0 -
followed your instructions, the danfoss thermostat is still in position
I have no power to the Tado controller but when I reverse what you said in your last message I have power at the Tado controller
Also pin 9 was reading zero
I do appreciate your help with this
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Point E in your message pin 1 and pin 2 went live 240v
I have the Tado controller working and the Danfoss thermostat set at 30 degrees, the Tado app I have the heating set at 22 degrees so I will see if the Tado app switches off the boiler at 22 degrees or if it continues to climb towards the 30 degrees or see what happens
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Tado controller is controlling the on/off times for both hot water and central heating , hot water side working fine, heating side temperature is being controlled by the Danfoss thermostat.
If I disconnect the Danfoss thermostat the wireless Tado thermostat does not take over and the boiler does not get the signal to come on
I totally agree with you that something needs to be done in that central wired junction box or should I have had a Tado wired thermostat, Tado said no, although are still unable to tell me what needs to be done
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will be out of country with my work for next two weeks, hopefully I can reconvene with a possible solution when I get back
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