"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Mark Trueman wrote:

"Set Square" wrote in message
...

With your existing setup, all you can really do with a room stat is
switch the pump on and off - so, whenever heating is selected by the
main programmer, the boiler will cycle on its own stat - and the DHW
will continue to get hot(ter) by gravity circulation.

Which i think it does now anyway, we tend to set the boiler to "1"
(its an old baxi back boiler), and let it heat the water as it sees
fit.

If i install the stat, is this no longer going to happen?

A room stat on its own won't fix it - although it will prevent the
radiators
from getting hot when they're not needed.

The problem with having no controls on the DHW temperature is that you
can't
run the hot water and radiators at different temperatures. Ideally, the
water going to the radiators needs to be at about 80 degC - which means
that
the boiler needs to run at this temperature. However, this will result in
the DHW being heated to approaching 80 degC - but it needs to be limited
to
60 degC, otherwise there's a severe risk of scalding. If you run the
boiler
cooler to limit the hot water temperature, the radiators won't get hot
enough.

If you control the gravity hot water flow in the way I suggested in my
previous post (by using a zone valve and cylinder stat) you can have the
best of both worlds - hot radiators without the DHW getting too hot. You
also get the added bonus that it shuts the boiler off when both CH and DWH
demands are satisfied, thus saving energy (and money!).

You have just summed up my problems well. Yes, the water gets too flipping
hot in the winter as we have to turn the temp up on the boiler in order to
get the rads up to a nice temp

So im looking at converting to a c-plan, which doesnt look too hard, once i
get my head round the electrics. I think the way this is wired up currently
is a total botch job so it may take some working out!! Is there an easy way
to wire in the cylinder stat and 2 port valve by just using the connections
available to me in the LP241 controller. This would also make wiring runs a
lot easier. Connecting anything to the pump is definitely out of the
question, as its not easily accessible.

Im pretty competent at electrics and plumbing but havent ever done any ch
wiring before so any tips would be happily received