Furnace board common connection?

[aubreytrotter]

I've discovered there are three wires (1 unused) between my room thermostat (currently battery powered)and the board on my furnace (Johnson and Starley Hi spec m31). My question; is there a simple way to connect this third wire to the board to use as a common wire so I can use a better thermostat. Any help would be greatly appreciated. Many thanks

 

[Madrab]

If you are talking about giving it permanent power then you just need to hook into the same terminal as the live input on the board as long as the boiler is fed from a 3A protected supply. Though you would really need to take 2 if not 3 all three - Live ,Neutral and poss earth - not just a live to properly power a thermostat.

That being said, and not wanting to sound cheeky but if you actually have to ask how you would take a mains supply from the board, then I would suggest you shouldn't really be playing about with mains power cables. Could cause a lot of damage to you, yours and the boiler.

 

[DP]

Third wire is earth conductor. Stick with battery powered unit Or go wireless.