convert from Nest heat unit

rolandwb

I cannot seem to get tado to work correctly . Following the tado instructions but nest has a single loop from 2 - 5 and an extra wire not mentioned in any of the tado instruction. Have contacted tado by email as advised but as of yet no reply.

Thoughts on how to connect to the tado extension with c/h and hot water? I have tried a like for like without the link and 1 wire that i assume not required. I have had it all paired up pefectly with battery room stats but it seem that the boiler runs all the time.

Cheers

policywonk

Well done. Please close this thread as 'accepted'.

policywonk

What is your boiler's specific model?

Does your house have an S Plan or Y Plan, and if S Plan, how many zones does it have?

rolandwb

s plan independent valves for water and a single heating zone. Boiler is a Ideal logimax S30.

Cheers

policywonk

Your boiler handles Opentherm digital controls. Now Gen 3 of Nest also handled Opentherm, but I see it wasnt wired in. If you want to remain using your boiler in simple on-off switched heating, do the following:

1. Check how the wiring centre near the boiler is wired. Look up the S Plan Central Heating Controls and Zoning - DIYWiki and make sure your wiring centre makes sense.
2. Check whether your Nest controller is wired to match this:

3. Purchase a mains testing screwdriver and see if your Nest station behaves like this:

• Pins L, 2 and 5 are permanently LIVE.
• Pin 3 only goes live when there is a call for central heating (so swing the thermostat up, and does it fire the boiler and does pin 3 go live?
• Ignore Pins 1 and 4. Yours arent wired.
• Pin 6 only goes live when your HW cylinder stat wants heat.

Am particularly troubled. Your PIN 6 has a green/yellow wire handling a HW tank call for heat. Please check that this wire actually goes all the way back to the cylinder and serves as switched live, not earth?

If thats all real, then this is how the change should map to a Tado wireless receiver:

• N to N
• L to L and a bridge is added to CH-COM and HW-COM
• 3 to CH NO
• 6 to HW NO.

It should work. However it isnt safe. There should be a wire going to Earth when the Tado is fitted. It switches mains voltage relays and when these fail there is a risk - which must be removed by a genuine earth wire. It should have been there with the Nest and it was irresponsible to be commissioned, with Earth not fitted.

Let us know how things go.

rolandwb

Thanks the nest thermostat is wire free as will the tado be. whether that makes any difference.

on the tado do you need links are they not internally linked.?

policywonk

Hey mate. The statement 'the nest thermostat is wire free, as will the tado be…'. Am genuinely confused. It cant be wire free.

• What did you mean by stating that?
• Did you remember to use a mains testing screwdriver as recommended in the previous post? What did you find?
• Did you mean to state that there is no voltage registered by a mains testing screwdriver?
• Or do you mean to state that the wiring is Opentherm, which is volt free?

The Tado wireless receiver seems to be the BU model, ie the early version of the V3s used in the UK. Are you trying to move your boiler into Opentherm control mode?

Are you uncomfortable with conducting diagnostics on this wiring? If so, you will need to involve an electrician.

rolandwb

Thanks again I meant that the nest stat is connected by wifi. as will the tado stat be.

There is no opentherm connection made.

I have tested the nest as you mention and all seems fitted as you stated, the terminal 6 green wire is indeed a live switch wire needs a sleeving colour. I will add an addition a single earth loop as the main connection box it is only inches away, for safety as advised.

rolandwb

Thanks for your help bit the bullet and bought upto date receiver worked straight off as described. So will see what happens..

Cheers fella