New room thermostat but it's not 'clicking'

[Dr oberts]

I'm wanting to switch my analog room thermostat for something a bit less yellow...

Based on how the current one is wired (pic attached) I assumed it was a 3-Wire Installation one I needed and went for this one:
https://www.screwfix.com/p/drayton-rts1 ... _container

However, when installed it doesn't 'click' to notify the temp, so doesn't turn the heating off at any point as the house heats up.

For ref: I wired 1 (old thermostat) to L (new), 2 to N, 3 to 3/Call

Hope that makes sense. Is there anything I'm obviously doing wrong and can be fixed? Or have I picked the completely wrong new thermostat in the first place?!

Any help/advice much appreciated

[ericmark]

The black wire is neutral, it is not needed, the thermostat will work without it, however with it connected it will reduce the hysteresis.

There is nothing to identify the two red wires, one is feed in, and one is feed out, if the wrong way around the hysteresis reduction will not work as it should, but thermostat will still work.

If the black neutral wire it put in wrong place it can cause damage. So if not sure, don't connect.

So old black should go to N and other two to L and 3, So 2 = N, 1 = L and 3 = 3.

Personally I would use Flomasta 22199SX Wired Digital Programmable Room Thermostat (6259G) screwfix number, it is two wire so black not used, just the two reds, and it does not matter which way around, and it also has a programmable function.

Even with nothing connected the new thermostat should click,