Nest with ESi

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littlecharva

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Hi,

I wired up my Nest (3rd gen) fine in my old house a few years ago, but have just moved into a new build and the heating system is WAY more complicated than the last one! We have a boiler in the garage, hot water cylinder in a cupboard upstairs, programmer in the utility room and two zones with a thermostat each upstairs and down.

I've opened most things up and it seems like the most logical place to wire the Heatlinks (I'm gonna buy a second Nest for the other zone) is in a box on the cylinder which has the following in:

IMG_3337.jpg


Am I on the right track so far?

If so, there is a block there for Room Stat 1 and Room Stat 2 with junctions for:

L E N L/1 N N/O

With wires going into L, E, N and N/O. I assume these wires run off to each of the thermostats - right so far?

So would it be a case of pulling out the L, N and N/O and then wiring the Heatlink L and N into the L and N junctions and the 3 into the N/O? What about the 2 in the Heatlink, would I wire that into the N also? Would it matter which N junction I wire it into?

Assuming I'm on the right track so far, I could then take the L and N I previously pulled out, and wire them into the T1 and T2 of the Heatlink and then wire the other ends into the Nest?

Is it possible it's that straight forward?
 
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It's a while since I've seen one of these, but I seem to remember the wiring for the room stats to be as below:

Room Stat 1 - (L1) (N) (N/O) and in a similar vein, Room Stat 2 - (L1) (N) (N/O)

The white lines on the edge of the PCB separate the terminal functions and I believe the L E N you refer to will be outside of the room stat separation line. If that's the case, then I would disconnect the existing thermostat cable(s) and, assuming that you have already connected the 230V mains supply and earth to provide mains power to the Heat link, then:

Then esi Room Stat terminal (N/O) goes to to Heat link (3) 'Heating call for heat'

Heat link (2) 'Heating Common' is connected to the Heat link (L)

One of the Heat links can also be used to control the hot water heating using terminals (5) and (6) if I see your photo correctly and from memory of the terminal layout, there appears to be a grey wire in the esi Programmer 'HW On' terminal? if so, that wire goes to Nest (6) 'Hot water call for heat' and Heat link 'Hot Water Common' (5) is linked to the Heat link (L & 2)

Looking at the wiring as much of it as I can see, I believe the programmer may only be controlling the hot water on/off times and the existing room thermostats are of the programmable type. Is that correct?

Once the existing room thermostat cable(s) have been disconnected completely from the existing wiring, you may use two of their cores to connect the Heat link T1 & T2 to the Nest thermostat T1 & T2
 
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Hi Stem, thanks for your response - much appreciated.

No, the thermostats aren't programmable, and the programmer should be controlling both heating and hot water. Although I haven't changed the programmer from "always on", so can't confirm if it actually works like that. It's a brand-new house, so I wouldn't be surprised if they'd f**cked that up too! :)

I'm happy to leave the programmer controlling the hot water, as I'll probably leave that set to "always on" too.

Here are a couple of other photos:

IMG_3338.jpg
IMG_3340.jpg


So there are wires coming out of L E N on the section marked PUMP (next to STAT1) and MAIN (next to STAT2), but only one wire connected to each STAT in N/O. I assume the stats have just had their live and neutral wired to the wrong bits?

So should I wire the Heatlink as follows?

L > L/1
N > N
2 > L/1
3 > N/O
 
My assumption about the programmer was made because it appears that there is only one wire connected to the programmer terminals at the esi [Grey wire in HW On?] all of the other programmer terminals look empty and if that is the case L/1 will never be made live, and explains why it isn't connected to anything now because it's a dead terminal.

Therefore you would be better to connect it as I described originally. A separate 230V mains supply via the same 3A fused spur as everything else to provide the Heat link with a permanent power supply, and only the N/O of the esi wiring centre Room Stat terminals connected to Heat link (3) Heating Call for Heat.

If you wish to test L/1 and N with a multimeter and find that they do provide a permanent mains supply then you could do as you describe. But I would be surprised if this was the case.
 
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