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!).
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.