Wiring salus rt500 help

[AlexS47]

Hi, I what to change my thermostat... the old one was a potterton prt100 st and the new one is a salus rt500.
At the potterton prt100 st I have 3 wires :
Blue is in 4 - N
Red is in 2 - H
Yellow is in 1 - TL

At Salus rt500 I have
L and SL no N.
Can you please tell my what wire goes in L and what wire goes in SL and what I do whit the wire in N.
I mention I have central heating Vaillant ecotec pro24. Thanks

 

[stem]

I suspect that the wiring at your original thermostat is incorrect. Normally the red wire would be used as Live (1) and the Yellow as the switched live (2). So there are two possibilities here, either the original installer has used the the yellow as live, and the red as the switched live, or the wires are transposed. If they are transposed, whilst this would have the effect of causing the existing thermostat to work but be less accurate than it should be, fortunately it doesn't matter with the Salus.

So the red and yellow wires go to Salus (L) and (SL) Normally the Live would go to (L) and the switched Live to (SL) but fortunately it will work the other way around.

The neutral isn't needed so usually it is put in a separate insulated screw terminal and tucked out of the way.