Google Nest Installation Advice

[nestnoob]

Hi All,

Looking for some advice regarding the compatibility of a Google Nest to replace existing Drayton timer and stat. I know the Nest is compatible with my S Plan system generally but cannot see how I would wire the new stat into the T1 and T2 ports on the Heatlink (which is a 12v connection?). Stat in hall, timer in kitchen with boiler, everything else 2 stories up in airing cupboard (motorised valves, pump, cyl stat, control centre etc). A heating engineer friend said I'd either have to run a new cable somehow or use it completely wirelessly detached from the wall. I'd rather plumb it in so i can get rid of the ugly existing stat and know i wouldn't lost the new stat.

I've attached some photos, unfortunately the wiring centre looks a complete snake's breakfast and not easy to see where the wires run, I'm sure this could be tidied up. I'm planning on getting someone into to do it but want to know whether it's a non starter and worth going with the Drayton equivalent which I believe is just plug and play with my system.

Cheers

 

[CBW]

To do what you’re asking, you’d need to install the heat link where the wiring center is, and use the wires that go to existing thermostat, and alter the wiring needed for the heat link and zone valves there.

 

[nestnoob]

Ah ok, this was at the back of my mind. Wireless signal is dreadful on my 2nd floor so has no chance of the stat in the hall communicating with the heatlink.

Would the timer then be disconnected and made redundant or would it have to be included in the equation but effectively set to permanently on for both hot water and central heating?

 

[ianmcd]

The T1 and T2 are 12v power supply from the hub to the nest thermostat to save you using the USB cable to supply power to the thermostat, they dont switch anything whatsoever, if wifi connection is a problem using T1 and T2 will help

 

[stem]

There are two versions of Google Nest. Nest-e and 3rd Generation. The installation is different for both, Nest-e simply replaces the existing room thermostat and the programmer is retained and set to have the CH permanently 'on' as you describe (but not the HW). On the other hand 3rd generation replaces the programmer, and the old thermostat is removed.

Your posts are a bit confusing, some things you refer to in your posts apply to both versions. Which version are you considering?

 

[nestnoob]

Sorry should have said, considering the 3rd gen so can use it to set hot water schedule and central heating. I have looked at the nest e and it's still in the mix but would still need to use both systems for hot water. With all the faff it might be, I may leave well alone or go with the Drayton wiser which will directly replace the existing timer switch but would have to leave the ugly Drayton stat on the wall albeit disconnected

 

[CBW]

Would the timer then be disconnected and made redundant or would it have to be included in the equation but effectively set to permanently on for both hot water and central heating?

You should be able to disconnect it permanently, but obviously need the wires at the other end wiring into the heat link

 

[nestnoob]

To disconnect I assume the elec would terminate all the lives together, neutrals together and earth's etc, replace with blanking plate and then the same the other end while putting some new cable to the same terminals in the wiring centre but to the heat link instead?

 

[stem]

When it comes to the wiring, the Drayton programmer and the Nest are both just two simple switches one is simply exchanged for the other.

The Drayton programmer connections are.....

.....so, all of the existing wires are transferred from the Drayton to the terminals at the Heat link that have exactly the same function as shown below.

So in your case:

1. CONNECT THE HEAT LINK

Wires in Drayton N, L, E.....> Nest N, L, E

Brown Wire in Drayton 3 (HW on)....> Nest 6 (HW Call for heat)

Black Wire in Drayton 4 (CH on)....> Nest 3 (CH Call for heat)

Then both Nest 'Common' terminals 2 & 5 should be linked to Nest L terminal

2. CONNECT THE NEST THERMOSTAT
If you wish to power the Nest thermostat from the Heat link then T1 and T2 at the Heat link are connected to T1 & T2 at the Nest thermostat, or alternatively use a separate plug in power supply for the thermostat.

3. DECOMMISSION THE ORIGINAL THERMOSTAT
The old thermostat should be decommissioned to stop it interfering with the Nest. The easiest way for DIY, if you don't mind leaving the old stat in place, is to move the black wire from terminal 3 of the thermostat and put it in the L terminal with the brown wire. This way there's no need to touch any of the wiring at the wiring centre.

If you do want to remove the old thermostat, it involves tracing the thermostat cable back to its origin at the wiring centre. [In your case it looks fairly easy as the wires are labelled] When the origin is found, note where the brown and black wires are connected. The cable can now be disconnected and removed completely a wire inserted between the two terminals where the brown and black wires have been removed from completes the circuit.

Whether the old thermostat cable, once disconnected, can be used to connect the Nest thermostat to the Heat link T1 & T2 will depend on how the original installer wired it in. It's unusual for it to be located close to where the Heat link is.

The black cable going to the motorised valve is not secured properly it should be fixed under one of the cable clamps at the bottom of the wiring centre, something like this:

As it stands only the thin copper connections are holding yours in place, it could easily get snagged, pulled out of the terminals and expose live wires.

 

[ianmcd]

There are two versions of Google Nest. Nest-e and 3rd Generation.

nest E doesnt have T1 & T2 it is battery powered

 

[nestnoob]

Many thanks, I'll probably leave alone, it seems far too complex and my system is sensitive enough as it is without further complexity. I will take care of the motorised valve cable though, I had it replaced 12 months ago and looks like bad practice, the original cable went through the back of the centre, through the wall and out at the valve. I may try and feed this back through

 

[stem]

nest E doesnt have T1 & T2 it is battery powered

I know, I saw that, and suspected that would most likely be the case but the OP also spoke of leaving the programmer in place which is Nest-e, and not Nest 3rd Gen. It's not unknown for an OP to have just picked up the terms from the internet, without realising which Nest it referred to.

Just thought it sensible to check [having been caught out before] hence my comment about mixed messages.

Your posts are a bit confusing, some things you refer to in your posts apply to both versions. Which version are you considering?

 

[ianmcd]

I know, I saw that, and suspected that would most likely be the case but the OP also spoke of leaving the programmer in place which is Nest-e, and not Nest 3rd Gen. It's not unknown for an OP to have just picked up the terms from the internet, without realising which Nest it referred to.

Just thought it sensible to check [having been caught out before] hence my comment about mixed messages.

Sorry mate , I knew you would know, it was a general comment for the OP and others reading the post thinking of doing similar, totally agree about the mixed messages, so many try to sound smart by quoting stuff from other posts , that have nothing to do with their set up

 

[Radiator woes 34]

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[nestnoob]

I wonder if someone could advise how the pump is connected to the boiler in this setup. The pump has an overrun facility but doesn't look like it's directly connected to the pump in the wiring centre. Could it be junctioned through the programmer?