Nest Heat Link wiring - pump always on

[jackthom]

When they are to be used in place of a wireless connection, the T1 and T2 connections are meant to be connected to the corresponding heatlink connectors which supply 12V to the nest.

Was mains 230V still connected to those wires?

 

[OliMortimer]

When they are to be used in place of a wireless connection, the T1 and T2 connections are meant to be connected to the corresponding heatlink connectors which supply 12V to the nest.

Was mains 230V still connected to those wires?

I had everything switched off whilst wiring the Nest in, but it didn't go bang when I switched it back on...I assumed (a dangerous thing) that the existing thermostat was at a lower voltage. I'll check tonight to see what voltage it's at, as I'm surprised I didn't melt the Nest thermostat...

 

[OliMortimer]

So am I right in saying that it should be;

* Disconnect cables from CH ON and R/S ON to the old thermostat
* Reconnect these cables to the Heat Link T1 and T2
* Remove current thermostat and replace with the Nest thermostat - will now powered from the Heat Link
* Disconnect R/S ON to CH Valve
* Reconnect CH Valve to Heat Link 'call-for-heat'
* Connect Heat Link L and N to L and N

 

[jackthom]

So am I right in saying that it should be;

* Disconnect cables from CH ON and R/S ON to the old thermostat
* Reconnect these cables to the Heat Link T1 and T2
* Remove current thermostat and replace with the Nest thermostat - will now powered from the Heat Link
* Disconnect R/S ON to CH Valve
* Reconnect CH Valve to Heat Link 'call-for-heat'
* Connect Heat Link L and N to L and N

Yes that looks good. Don't forget the short wire link inside the heatlink from Live to Common.

You can leave the CH valve wire in it's current position as long as the only thing left connected to it is the heatlink 'call for heat'.

 

[OliMortimer]

Thanks for all your help. I really appreciate it.

I'll alter the diagram with the Nest added, just to confirm that everything looks ok, before I tackle it again...

 

[SilentDancer]

You'll need a programmer to time your hot water otherwise you'll waste money heating your cylinder 24/7 and it doesn't comply with building regulations. Nest is only suitable for combi boilers.

 

[OliMortimer]

Ok, so altered the diagram to include the Nest Thermostat and Nest Heat Link.

* R/S ON is no longer connected to anything
* CH ON is only connected to the programmer now, so guess this means CH doesn't need to be on at all on the programmer?
* Heat Link runs off L and N on the main junctions
* Heat Link call-for-heat runs into the CH Valve

Does this look ok?

Final Nest Wiring (Not Labelled)

• OliMortimer
• 4 Dec 2014
• 1

High res before: https://www.dropbox.com/s/xsrtdj7g8pblnd4/Heating Wiring GUESS 2.png?dl=0
High res with Nest: https://www.dropbox.com/s/i0m6ptpbz4njn1r/Heating Wiring GUESS NEST.png?dl=0

 

[OliMortimer]

You'll need a programmer to time your hot water otherwise you'll waste money heating your cylinder 24/7 and it doesn't comply with building regulations. Nest is only suitable for combi boilers.

Yeah the current programmer will stay on to control the HW.

 

[mikeyd]

I replied to a similar topic in the electrical forum here //www.diynot.com/forums/electr...mostat-to-potterton-condensing-boiler.419868/
I didn't realise that the OP of that thread had cross-posted here //www.diynot.com/forums/plumbing/nest-thermostat-integration-to-potterton-heater.419866/

OliMortimer,
The nest is just a thermostat replacement. I think you now realise you didn't need to worry about rewiring the boiler. The Heatlink replaces the thermostat and the nest connects to it and turns the heating on and off just like a thermostat but it also knows what time it is. (So you must set the programmer to heating on constant)

Where are you going to put the remote unit? It has a built in PIR, light sensor etc. I haven't installed the one I have under the tree but you need to think about where it will best work.

 

[OliMortimer]

I replied to a similar topic in the electrical forum here //www.diynot.com/forums/electr...mostat-to-potterton-condensing-boiler.419868/
I didn't realise that the OP of that thread had cross-posted here //www.diynot.com/forums/plumbing/nest-thermostat-integration-to-potterton-heater.419866/

OliMortimer,
The nest is just a thermostat replacement. I think you now realise you didn't need to worry about rewiring the boiler. The Heatlink replaces the thermostat and the nest connects to it and turns the heating on and off just like a thermostat but it also knows what time it is. (So you must set the programmer to heating on constant)

Where are you going to put the remote unit? It has a built in PIR, light sensor etc. I haven't installed the one I have under the tree but you need to think about where it will best work.

Unfortunately our thermostat only has two cables connected to it - L and N. Seems that power is only running through L and N when there's no call-for-heat - if you put the thermostat temp up above what it is currently, there's no longer power running through it.

I'm putting the Nest thermostat in place of the current thermostat, so looking to wire the Heat Link into the airing cupboard when the junction box is.

Could someone confirm that the before and after now look ok to proceed please?

Original Wiring

• OliMortimer
• 4 Dec 2014
• 1

Final Nest Wiring (Not Labelled)

• OliMortimer
• 4 Dec 2014
• 1

 

[jackthom]

The diagram looks OK but as the nest connections don't have labels this is just to confirm...

In the Heatlink, 'Live'; 'Neutral'; Short link from 'Live' to 'Common'; 'Call For Heat' to the wiring centre CH valve (wire that was in R/S ON). Also heatlink T1 & T2 go to corresponding terminals in the Nest thermostat.

 

[OliMortimer]

The diagram looks OK but as the nest connections don't have labels this is just to confirm...

In the Heatlink, 'Live'; 'Neutral'; Short link from 'Live' to 'Common'; 'Call For Heat' to the wiring centre CH valve (wire that was in R/S ON). Also heatlink T1 & T2 go to corresponding terminals in the Nest thermostat.

Excellent thanks! I'll upload a new image with the Heat Link connections labelled, for anyone looking in future.

 

[OliMortimer]

Forgot to update this with the labelled diagram:

Final Nest Wiring

• OliMortimer
• 14 May 2015
• 1