I am replacing my sunvic 2259 thermostat with a sunvic 4101, but can't
make sence of the wiring.

The 2259 has 3 connections and the earth connected to a metal back
plate, while the 4101 has connections COM, DEM, SAT, and N. I can't
figure out which wire to stick where.

I have read an earlier post on there where the poster had 3 wires -
red, black and unsheathed. But i have 4 wires, blue, red, yellow and
unsheathed.

All help gratefully recieved...running out of 3 amp fuses now lol.

Thanks in advance.

Matt.