What does this instruction on my thermostat back plate mean?

[therafox]

Hey all, I'm currently trying to better understand how the Emmeti CS-11 thermostat in my room works. I removed the back plate and found the wiring looks like this:

I'm a bit confused with the instruction on terminal 3 - what does "link terminals 1 to 3 for 230VAC live output" mean? They are currently linked together in my setup.

Does this determine whether the output is NO or NC?

 

[RF Lighting]

The switching of your thermostat happens across terminals 3&4. What ever voltage you connect into terminal 3 will be outputted by terminal 4 when the stat is calling for heat. It is normal to have a 230V output on a standard heating system.

 

[EFLImpudence]

It might have been better to say "Link terminal 1 to 3" or "Link terminals 1 and 3".

Lucky it's not "Link terminals 1 2 3".

 

[therafox]

Ah, got it! So if 1 and 3 aren't linked, it simply doesn't work? I guess the reason is if the output needs to be on a different voltage, then I'd need that voltage to link into 3?

 

[ericmark]

Yes some boilers are 230 volt (low voltage) and one can use link, and some are 24 volt (extra low voltage) in which case no link, and some are variable voltage 0 - 40. And some have all three and you can select which to use.

Most motorised valves are 230 volt, there were some 24 volt, but mostly now gone. But the micro switch in two port valves can be 24 volt when the motor is 230 volt, but three port no option but 230 volt.

The same with thermostats, some are 230 volt only, some are what is called volt free, which is what yours is so you can select if 24 volt or 230 volt, and some are 0 - 40 volt.

Just to make it more complex some thermostats use both, so the 230 volt works a motorised valve and the 0 - 40 volt works the boiler.