In an earlier contribution to this discussion,
Roger wrote:


How happy are you with meddling with mains wiring. If you disconnect
the tank thermostat and the problem goes away then you are on the
right track and circumstances should have proved that the timer is
either defective or not controlling the DHW.

Opening up the programmer and looking at the wiring should at least
show whether or not the domestic hot water channel has been wired up.
That might be the more sensible first step (after isolating the
mains). That way you might get an instant answer to the question of
whether the wiring is wrong.

Before the wiring can be checked sensibly, the OP needs to know what it
*should* be like - which in turn depends on the system configuration.

The OP *thinks* that there is only one zone valve - but hasn't yet confirmed
that there *is* only one, and that it has 3 ports.

[The sypmtoms sound to me much more like one of two 2-port valves stuck
open, rather than a 3-port valve problem].

Assuming that it *is* a single 3-port valve, it might be a diverter valve
(W-Plan) or a mid-position valve (Y-Plan) - and the wiring is substantially
different between these two options - and different again for an S-Plan
system with two 2-port valves.

May I suggest that the OP has a look at the Honeywell documents at
http://www.honeywelluk.com/article.aspx?ai=faq [1] in order to work out what
he's actually got, and then reports back here.

[1] ********! Honeywell have changed their site, and the document I wanted
to reference ain't there any more. However, the reference I've given appears
to offer information about S, W and Y plans - once you've registered
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!