Room Stat Wiring for New Replacement Thermostat Ask questions and find answers to many subjects relating to electrics and electrical work

[falconer2406]

Hi All, A problem with my heating lends me to believe that I need to replace my old analogue room stat. I have had a new digital stat for some time haven't got round to installing it. The wiring for the new stat seems easy enough but I would be grateful if I could check with you guys please. My current stat has four wires, Red, Yellow, Blue and earth. they work as follows Red constant live, Yellow switched live (becomes live when I turn up the stat) Blue is I assume neutral as it doesn't show live at all at any time.
The new stat requires live to COM so I assume that's the constant live red? and then neutral to NC I assume that's the blue? it doesn't indicate that a third wire is required but does have an additional wiring terminal marked up as NO is that where the yellow switched live goes please?
In summary Red constant live to COM Blue neutral to NC and Yellow switched live to NO.
Appreciate any help and feedback guys, many thanks

[ericmark]

NO

The old thermostat had a heater which reduced the "slewing range" as it is called with new digital models and this needed a neutral.

Many new types use batteries to power the device and neutral is simply not used. Just put it is some connector block in case at a future date you use one that is not battery powered.

Connecting neutral to N/O, N/C, or Com will destroy the thermostat.

[falconer2406]

Many thanks Eric my new one does have batteries. So for clarification red permanent live to COM and yellow switched to NC blue to terminal block and away we go?

[falconer2406]

Many thanks Eric my new one does have batteries. So for clarification red permanent live to COM and yellow switched to NC blue to terminal block and away we go?

[ericmark]

Yes blue wire is now not used just make it safe. I often just double over and tape I double over so copper can't poke through tape.