I was hoping to go and buy a Nest thermostat tomorrow to fit to our heating system (system boiler, Y Plan setup). We don't currently have a room stat.
I understand the wiring in the junction box in our airing cupboard and how the system works.
The Heat Link box that comes with the Nest is wired into the junction box and communicates with the stat wirelessly. The room stat is powered by either a USB plug adaptor or can be wired into the heat link using its 12v DC terminals.
Currently, the heating common and call for heat terminals in the junction box are connected with a small jumper cable, meaning there is a constant call for heat when the programmer switches on the heating. I plan to remove this and reuse it to connect the live and common terminals in the heat link, bypassing the programmers heating circuit entirely (the Nest will handle heating exclusively, the old programmer will just do water). I need to connect the Heat Links permanent live and neutral to the same in the junction box. Finally I need to connect the call to heat terminals. I haven't decided whether to hard wire the stat to the 12v connection or not yet, depends on where we want too place it.
My questions are:
* What cable can I use to connect the live/neutral/call for heat terminals? I guess 3 core + earth or 4 core flex might be suitable, but I only need about 30cm of cable. Maplins are the only local shop who sells cable by the metre and they don't sell either of these. Could I use twin + earth and use sleeving to identify the earth as a switch live? Probably not good practice I know but it wouldn't be the only misused earth cable in the JB (cylinder stat uses earth sleeved wire for the water satisfied link). Or would I be better getting a length of two core cable and using two runs?
* Whatever cable I can use, what rating should it have? Can I use flex? 1.5 or 2.5mm? It's all one the load side of the FCU feeding the JB of course.
* If I do run some cable for the 12v DC link to the stat, what cable should I use for this? I only need two cores.
As an alternative to getting some pre cut cable, I need to do a bit of rewiring in the under stairs cupboard. There's a badly fixed double socket spur which I plan to replace with an FCU so I can run a spur of that to a better located (and secured) plug socket and also a new light and switch. If I can use the same cable for this and the stat wiring then I might just buy 10m from the local shed and be done with it. Maybe 1.5mm T+E?
Thanks.
I understand the wiring in the junction box in our airing cupboard and how the system works.
The Heat Link box that comes with the Nest is wired into the junction box and communicates with the stat wirelessly. The room stat is powered by either a USB plug adaptor or can be wired into the heat link using its 12v DC terminals.
Currently, the heating common and call for heat terminals in the junction box are connected with a small jumper cable, meaning there is a constant call for heat when the programmer switches on the heating. I plan to remove this and reuse it to connect the live and common terminals in the heat link, bypassing the programmers heating circuit entirely (the Nest will handle heating exclusively, the old programmer will just do water). I need to connect the Heat Links permanent live and neutral to the same in the junction box. Finally I need to connect the call to heat terminals. I haven't decided whether to hard wire the stat to the 12v connection or not yet, depends on where we want too place it.
My questions are:
* What cable can I use to connect the live/neutral/call for heat terminals? I guess 3 core + earth or 4 core flex might be suitable, but I only need about 30cm of cable. Maplins are the only local shop who sells cable by the metre and they don't sell either of these. Could I use twin + earth and use sleeving to identify the earth as a switch live? Probably not good practice I know but it wouldn't be the only misused earth cable in the JB (cylinder stat uses earth sleeved wire for the water satisfied link). Or would I be better getting a length of two core cable and using two runs?
* Whatever cable I can use, what rating should it have? Can I use flex? 1.5 or 2.5mm? It's all one the load side of the FCU feeding the JB of course.
* If I do run some cable for the 12v DC link to the stat, what cable should I use for this? I only need two cores.
As an alternative to getting some pre cut cable, I need to do a bit of rewiring in the under stairs cupboard. There's a badly fixed double socket spur which I plan to replace with an FCU so I can run a spur of that to a better located (and secured) plug socket and also a new light and switch. If I can use the same cable for this and the stat wiring then I might just buy 10m from the local shed and be done with it. Maybe 1.5mm T+E?
Thanks.
