On Tue, 03 May 2011 13:33:49 +0000, mick wrote:

In your case, using an outside stat, you *may* have problems. Not
necessarily, because all heating systems vary. It will depend on your
heating load, the response speed of the heating loop, hysteresis of the
system etc. etc.

---8---

Try it. A single external stat is cheap enough and could still be used
if you later decide to try a return main stat. If you want to try a
"summer/ winter" select then just switch off the lag boiler.

Yup, that's my thinking. Start simple, if that's not good enough then's
time for plan B. They're only down the road from me and nice enough
folks, I think they'd understand if it takes a bit of iteration to sort
out what they already know is a weird system.

Only snag I see with my plan A is I should probably arrange to only fire
one boiler when there's only HW demand even when it's cold outside
otherwise I'm pretty much guaranteed cycling. But that's probably not
straightforward electrically. Dammit, now it's getting complicated again!


--
John Stumbles -- http://yaph.co.uk

An atheist is a person with no invisible means of support