Digi Room Thermostat

[Doug99]

I am replacing a manual rotary room stat with a battery operated digi stat and am seeking advice on its wiring. My existing Ferolli combi boiler has three wires running to the manual stat. Earth and 2 red. I have checked that with the boiler on 'heating' I have 6v dc across the 2 reds. There is no 240v ac.

The new digi stat has terminals marked NO / COM / CON which do not read across to the old stat. The earth lead is fitted because of the old metal back plate and can be ignored for the plastic digi stat, however, I am not sure which connections to make for the reds. Obviously one of the red wires will connect to COM, but which other terminal do I use for the second red - NO or CON??

I do not have a boiler manual for reference.

 

[Lectrician]

You need the stat manual - not the boilers!

You need clean contacts (which you have, as it is battery operated).

You are correct, one is com, it will not which red you put to this terminal.

The other red would make sense on NO (normall open). Try it and see.

If the boiler fires when you set the tempat 30deg, but not at 0deg, try the other terminal!