On Fri, 9 Oct 2020 18:54:21 +0100, Roland Perry wrote:

I'm not 100% sure what wiring the OP has, there is mention of two
wire and two wire plus L and N.

controller /------make-------\
| | | |

N L 1 2 3 4

| | | |

from to to
mains boiler boiler

But the more I look at it, the more I suspect that either 1 or 4 is also
tied to one or other of the N/L mains. Some testing required, because
the documentation is ****.

A lot of programablale stats time switches etc are "volt free" on the
contacts ie. not connected to the devices supply (mains or battery)
internally. The switching bits are mains rated so the actual control
circuit can be low voltage or mains.

I thought there was a standard wiring layout for thermostat back
plates but as with many standards there are so many to choose from...
I sort of side step that issue by bringing every connection from a
stat, switch, motorised valve, etc back to a wiring center and
fitting jumpers as required to create the correct circuit(s), I like
the ACL Lifestyle LWC1.

--
Cheers
Dave.