"Stormin Mormon" wrote in message
. ..
Most likely, two wires is how it was designed. Third wire could be
anything,
but probably a common.

It's possible the thermostat isn't the problem. I'll copy in the alt hvac
group, they field this question often.

Christopher A. Young
Learn more about Jesus
www.lds.org
.

"Daren Friday" wrote in message
news
Hi
We have a Potterton Suprema boiler, a Potterton EP3002 wall timer and a
Wickes wall thermostat.

The heating switches on OK according to the timer schedule but fails to
switch off when it reaches the right room temp set on the thermostat so
we just get hotter.

I had to have a new thermostat for some reason but I seem to remember
there being 3 wires into the stat but there appears to be only 2.

Is that right? And would the missing wire be the one to turn off the
heat?

The stat should only need 2 wires if its got batteries in it. The pictures
are of such small size and poor quality, I can't tell much else.
Its possible that you have been having this problem since you put the new
stat in.... most likely because the anticipator setting isn't correct, or
the temperature delta isn't set correctly, or both.