On Thu, 21 Oct 2004 18:27:12 +0100, Brownie wrote:

Hi,

I'd just like some help with rewiring a new programmable thermostat. I
think I know what to do but just wnat to be sure if possible.

Presently I have a standard Honeywell (T40) T6360B - the large dial
electro-mechanical type. I am getting a Horstmann Centaur 7, that has been
recommended in the group before. Apparently it's quite common for
installers to use standard 3 core flex to wire up the original thermostat
and these electronic replacements only need two wires. Presently the
Honeywell is:
No wires to Earth terminal, 'the Earth wire' to terminal 2, the Neutral wire
to terminal 3 and the Live wire to terminal 1.

Any idea which goes to which terminal on the Horstmann? I'm led to believe
'the Neutral wire' now on terminal 2 is redundant and the 'Heat Call' wire
(Earth on the flex presently) is likely to be required along with Live
currently on terminal 1?

Hope somebody can make sense of that?

Currently the three wires you have are live from CH timer, neutral and
switched live to the zone valve (or boiler directly sometimes).

Whatever the earth wire is begin used for should be disconnected both ends
and ideally reconnected to earth at the far end. There is a spare "no
connection" terminal in the CentaurStat 7 (#4 IIRC) which can be used to
park the earth at the thermostat end.

The remaining two wires go into terminals 1 and 2 on the centaurstat and
are connected CH timed live and the switched live at the other end.

The wire connected to neutral (whichever it is) is no longer required at
all.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html