wrote in message
oups.com...
Christian,

Thermostat was most definitely working before.

I have mapped the following to the Sunvic:

1&7 to Sunvic N
6 to Sunvic L
2 to Sunvic CH On
4 to Sunvic HW On

This left the earths (now choc blocked together, Sunvic has no earth
terminal) and the two extra wires which I have now determined are BOTH
live. These were wired in to 3 on the Randall. One of these is now into
the Sunvic CH On, and is giving me heating back, and I don't know what
to do with the other. Connecting it to Sunvic N blows the fuse,
connecting it to Sunvic L runs the heating even when the programmer is
set off.


I'm getting the suspicion that you have lost your way in a "Y-plan" system.
Try going to Honeywells site and looking up Y-plan. You then need to
determine where each cable from the Sunvic position actually go to before
you can proceed to rectify this cock-up