On Wed, 14 Jan 2004 23:12:44 +0000 (UTC), "Michael Chare"
wrote:

"Anthony James" wrote in message
...
Christian McArdle wrote:

Are there any pitfalls I haven't thought of?
Secondly, ensure that you have a cylinder thermostat. It sounds like you
have an S plan system. If no cylinder stat is present, you need to insert it
in series between the programmer "HW On" output and the hot water zone valve
motor live (normally brown) wire.

Right. NOw you've lost me. Where can i find out what an 's' plan
system is? Why do i need a cylinder stat if i dont have one at the moment?

If you dont have a cylinder stat at the moment, my guess is that you have
gravity H/W. i.e. Your pump only drives the Central Heating.

If you would care to read previous posts you would note that;

a) there are 2 zone valves already installed, so that puts gravity out
of the question.

b) there is a cylinder stat etc... (see a))

In this case you will always generate H/W when the C/H is on,

Typically the boiler is supplied with power whenever the time switch is on. The
boiler starts whenever the water temperature falls below a certain point. The
room thermostat controls the pump, i.e. the room thermostat supplies power to
the pump whenever the room temp falls below a certain point.

If you just replace the room stat with a programmable one, you will have to
leave the boiler on all the time and therefore generate hot water all the time.

You could avoid this by either:

a) Fitting a Danfoss Randall TP9 Programmer/Room thermostat to replace both
your current programmer and room thermostat. Possibly very easy to install as
you may well be able to use existing wiring. Less than £60 from plumbworld. The
TP 9 allows six room temp changes and two on periods per day for H/W. Can be set
to use a different program at weekends.

Already sorted that I think, wireless would guarantee no wiring would
be needed in addition to the stat.

b) Fitting a H/W tank stat and zone valve with micro switch (Honeywell C plan).
Requires plumbing work.
Arguable a better solution but you need to be careful plumbing wise to be sure
that you boiler wont mind having is ability to circulate water naturally
restricted.

c) Using and additional relay to supply power to the boiler when the pump is on.

Option a) can be upgraded to option b). Nothing would be wasted.

If it were me who asked the original question I would ignore all of
this as irrelevant or incorrect.


SJW
A.C.S. Ltd.