Nest 3rd Generation Thermostat(s) & Logic Combi ESP1 35

[Liffeywater]

Hi Guys

I have a Logic Combi ESP i35 boiler and plan to install my 3rd Generation Nest thermostat(s).

I was told that the boiler was dual zone and has ESI thermostats in the bedroom and living room. I have two 3rd Gen Nest's and two Heat Links that I want to use to replace them.

I have a couple of questions:

I can only see one thermostat in the wiring module - Is it dual zone and if so how do I wire the two Heatlinks so one controls upstairs and the other downstairs?

The existing thermostats - Are they 12V or 240V and can I use the existing wiring to power the Nest control units?

Thank you very much for any help you can offer.

 

[picasso]

You will have 2 x 2 port valves somewhere on your pipework and a wiring centre, the heatlinks are wired in to control the valves rather than the boiler, can you post up some pics of your system ?

 

[Liffeywater]

You will have 2 x 2 port valves somewhere on your pipework and a wiring centre, the heatlinks are wired in to control the valves rather than the boiler, can you post up some pics of your system ?

Thanks Picasso.

I'd noticed this morning that the upstairs radiators were on while the downstairs one's were not. There's a wiring box above the system that I'm mapping out just now, and I'll post that when I have them.

 

[picasso]

There should be a couple of these on the pipework, probably under the boiler...

 

[Liffeywater]

Ok, so here's the inside and underneath of the boiler... I've looked further down from the boiler but can't see any motorised valves?

 

[picasso]

If this is your wiring centre you will have to trace the wiring and change it for a bigger one, there is no way your going to be able to connect up two heatlinks in that space.

 

[muggles]

Ok, so here's the inside and underneath of the boiler... I've looked further down from the boiler but can't see any motorised valves?

View attachment 188021 View attachment 188022

Please put the casing back on your boiler. It's there for your safety and forms the room seal of the appliance. It should only be removed and refitted by Gas Safe Registered engineers capable of carrying out the Regulation 26.9 checks to ensure it remains safe

 

[stem]

I can only see one thermostat in the wiring module - Is it dual zone and if so how do I wire the two Heatlinks so one controls upstairs and the other downstairs?

As has been said, if you have a two zone heating system there will be two room thermostats each controlling a separate motorised valve to control the flow of water to the separate heating zones.

Both motorised valves will then control the boiler via the same single boiler connection, which means that you don't need to remove the boiler casing, because the motorised valves won't change and therefore neither will the wring to the boiler.

The new Nest thermostats will replace the existing ESI thermostats and control the motorised valves instead.

But first, you will need to find where they are located, which will vary from property to property. If it's a new build often they are in an upstairs cupboard. Generally they are side by side, something like this.

The wiring centre is usually located close by typically at the end of the leads from the motorised valves.

 

[Liffeywater]

Ok Picasso, Stem - thank you for the steer, that's really helpful.

These are located above the boiler and to the side of the spaghetti junction that is the wiring centre I posted the pic of above.

I've ordered a larger wiring centre which will arrive in the next day or two.

I take it that it's just a case of powering the two heat links, replace the two thermostat wires from the existing thermostats to T2/3 in the respective Heat Links for upstairs/downstairs and then take the existing 240V wires powering the existing thermostats and move those to take power from the Heat Link 12V source and attach those to the nest controls replacing the existing thermostats?

 

[stem]

That's them, and your description of the work sounds about right.

Each Heat link requires a 230V power supply connected to N & L. This should come via the same 3A fused connection unit that provides power to the whole heating system, so that when it's off the whole system is isolated. You can usually pick the 230V up from the wiring centre where the motorised valves are connected. The blue wire for the motorised valves will be connected to N and if correct convention has been followed, the grey wire to the motorised valves should provide a permanent L. But check with a multimeter first to be sure. [Very occasionally, the orange wire is used for the permanent live instead]

The two switching wires that go to the present thermostats as you correctly figured go to their respective Heat link terminals 2 and 3.

Once the original thermostat wires are disconnected completely, you can then use them to provide the 12v supply to the thermostats by connecting T1 and T2 at the Nest thermostat to the corresponding T1 and T2 terminals at the Heat link. Note: If you do use the Heat links to power the thermostats, an earth connection should also be made to the Heat link earth terminal just to the left of T1

Not sure why you need a larger wiring centre, though. The terminals you need are there already. I assume you have found the wiring centre, the wires disappear through the wall out of sight.

 

[MariusCugir]

Hi guys. Hope you all are doing well! I really need your help. Today I want to install a nest learning 3rd gen. I have this boiler (please see pic) I have read carefully all your conversions but I'm a bit confused. So I only want to install one...please explain me simple you can...where heat link must be connected to...where actually. By the way I have too....2 zones as well. Can anyone show me were I open...which box and what wires pleaseeeee. Thanks

 

[muggles]

Hi guys. Hope you all are doing well! I really need your help. Today I want to install a nest learning 3rd gen. I have this boiler (please see pic) I have read carefully all your conversions but I'm a bit confused. So I only want to install one...please explain me simple you can...where heat link must be connected to...where actually. By the way I have too....2 zones as well. Can anyone show me were I open...which box and what wires pleaseeeee. Thanks

Better to start your own thread rather than hijacking this one. You'll have two zone valves somewhere if you have two zones. You need to find those. You'll need two Nests.