New Thermostat wiring options?

nintenjo

nintenjo

nintenjo

Soldato
Joined
29 Nov 2002
Posts
2,672
Location
Midlands. UK
our thermostat (one that controls the boiler) is very old and I’m pretty sure very inaccurate. It’s a manual Honeywell dial type with 1 wire in and 1 wire out.

I’d like a smart thermostat that I can use HomeKit to control. But as I understand I need more wires to connect one (signal wires which I have but also main power) however I had planned to power it use a small spur from nearby wall outlet to the location.

But when I spoke to an electrician he refused to do this and said it’s not safe due to a possible ‘voltage differential’. Instead he said the only option is to run a new wire from the boiler directly (but since it’s around multiple corners / rooms it would be impossible to chase if through the wall and instead would be visible on the interior wall). I would not want that visible wire and chasing it behind all the walls does indeed sound difficult.

But my initial proposal still stands, as I have seen other folk on forums do as I planned and use a source from an outlet to power there thermostat.. so what is the voltage differential risk he talked about and is it not safe to do?? Conflicting advise.

As I understand the power voltage and signal voltage would not be the same since they would be separated by the thermostats electrics?

Anyone help clarify?
 
nintenjo said:
so what is the voltage differential risk he talked about and is it not safe to do?? Conflicting advise.
Click to expand...
yes don't know what he means - parents had a wireless dt92e honeywell installed , replacing manual,
it needed a mains supply adjacent to boiler, but pump+boiler has one adjacent anyway,
it just communicates via same 2 wires with boiler heatwax on heat off.

they can now put the wireless thermostat at a more central appropriate place in the living room.

they don't need a smart thermostat controllable via a phone, and/or controlling TRV's.
 
nintenjo said:
our thermostat (one that controls the boiler) is very old and I’m pretty sure very inaccurate. It’s a manual Honeywell dial type with 1 wire in and 1 wire out.

I’d like a smart thermostat that I can use HomeKit to control. But as I understand I need more wires to connect one (signal wires which I have but also main power) however I had planned to power it use a small spur from nearby wall outlet to the location.

But when I spoke to an electrician he refused to do this and said it’s not safe due to a possible ‘voltage differential’. Instead he said the only option is to run a new wire from the boiler directly (but since it’s around multiple corners / rooms it would be impossible to chase if through the wall and instead would be visible on the interior wall). I would not want that visible wire and chasing it behind all the walls does indeed sound difficult.

But my initial proposal still stands, as I have seen other folk on forums do as I planned and use a source from an outlet to power there thermostat.. so what is the voltage differential risk he talked about and is it not safe to do?? Conflicting advise.

As I understand the power voltage and signal voltage would not be the same since they would be separated by the thermostats electrics?

Anyone help clarify?
Click to expand...
Voltage won't be an issue, the boiler and what ever spur you are on about are on the same single phase supply, it becomes an issue with three phase.

It's not dangerous as such, but to isolate your thermostat properly you would need to isolate the spur and the boiler, so it would need marking up..

What thermostat are you looking at installing? Do they not do a wireless version? Then you would just install a receiver at the boiler and have the stat where ever you want.
 
Thanks for info, to help here is a bit more context:

So my boiler is in my kitchen, and my thermostat is currently in my hallway (not ideal since every time the front door opens the temp drops and heating responds). There is a socket about 10-20cm from the thermostat in the hall which i had planned to use as my spur but was concerned abou the voltage differential discussing above. I have no models / makes of thermostat planned but a hub + remote thermostat i can put in my living room would be better since i dont care much about the temperature in my hall. Suggestions welcomed.

My current thermostat is wired like this (if it helps):

Dropbox

www.dropbox.com www.dropbox.com
 
Last edited:
I'd forget about the wiring to the hall.

I'd look at something like the Hive thermostat as the actual stat is battery powered and you can place that anywhere you want (the batteries last ages)

Then the receiver for that would be installed right next to the boiler, it would run off of the boiler supply and is easy to install. Then the "hub" just goes next to your router or where ever you have network.

This allows you to run everything from the single circuit and the freedom to have the stat where you prefer, then just remove the old stat and patch the wall.
 
You must log in or register to reply here.
Back
Top Bottom