Thermostat installation help

[aiybn]

Hello guys

I am trying to replace an old analog honeywell thermostat with an ESI programmable single channel (model: ES1247B) thermostat. Upon removing the old one, I can see brown (live) and black wires. The ESI installation guide does not offer a wiring diagram but from some research I found out that brown wire (live) needs to go into 1 (COM) and black wire into 3 (ON).

The thermostat does not power on using this arrangement. Would greatly appreciate if someone can please guide me on this.

For reference, the backplate has five slots: N, L, 1 (COM), 2 (Off) and 3 (On). The esi thermostat has a backup 2032- 3V coin battery.

 

[muggles]

The ESI requires a permanent Live supply, so you need permanent Live to L, Neutral to N, heating common to COM, and switch live out to terminal 3. It won't work with just two cores.

 

[aiybn]

Ah right - the two other wires have been cut short and isolated, which then means they need to be retrieved and extended.

Does the following arrangement look correct to you? The brown (live) goes to L, green-yellow neutral (to be retrieved) goes to N, black goes to 3 and the grey (to be retrieved) to COM.

Thanks

 

[aiybn]

Here's the wiring arrangement from the boiler pcb for reference

 

[trojanhawrs]

Here's the wiring arrangement from the boiler pcb for reference

I don't see your thermostat cable in there. I take it you have a hot water tank and wiring centre?

 

[aiybn]

Nope, i just have a combi boiler and no hot water tank.

 

[trojanhawrs]

Where is the white cable on the top of that picture going?

 

[aiybn]

Here's the box which happens to be in a cavity where the hot water tank must have been in the past. The wire to thermostat goes down from here.

 

[trojanhawrs]

Here's the box which happens to be in a cavity where the hot water tank must have been in the past. The wire to thermostat goes down from here.

Left bottom cable to boiler, right bottom to thermostat correct?
Would you be able to run a new thermostat cable easily enough? Extending it on both sides is going to be crap. I'd go for a 1mm 4-core flex.

 

[aiybn]

Thats seems correct - 5 core cable to the boiler (matches with the boiler pcb) and the right one goes straight down to the thermostat.

On your point on running cable to thermostat, why is that needed? The current thermostat cable already has 4 cores. Its just that two of them have been trimmed - see the very first photo of thermostat backplate showing two long and two very short cables. Wouldn't I be able to get away with extending the two short ones that are trimmed to make them four again?

 

[aiybn]

If you think the above is a workable solution then I'm just left with figuring out which cables goes where in the thermostat.

 

[trojanhawrs]

If you think the above is a workable solution then I'm just left with figuring out which cables goes where in the thermostat.

I don't think it's a workable solution, which is why I suggested running a new cable. If that's unfeasible, my next suggestion would be to buy a wireless thermostat instead, and mount the receiver next to your "wiring centre", again with a new cable - edit : actually in this case you'd likely be able to cut back enough of your existing cable to retrieve the wires.

 

[aiybn]

Got it, thank you very much for your help!

 

[CountryFan]

My advice is not to use the green/yellow (cpc/earth) as a neutral. You have options with the existing wiring.