Hi All,
After a fair bit of research, and a weekend spent tracing out my existing plumbing, I thought I'd post an update.
The gravity circuit is near impossible so I can't do it. Basically there's not enough space in the loft around the edges of the room for me to get in and run pipes. Yes I can get in but access is really tight, and at under 10 stones, I'm pretty small. Unless I resort to a midget plumber, or ripping half the house to pieces it's a no-go.
So...
In answer to ericmark - it is possible to run a pumped system, and it does need to be triggered at a certain temperature to make sure the boiler runs efficiently and condensation isn't caused. But there should also be some additional protection. Here's what I think I'm going to do:
Pumped circuit through stove, triggered by temperature sensor behind stove so pump only runs when efficient temperature is reached.
small gravity circuit behind stove with heat exchanger, and dump connected to mains with a 95degree valve (so emergency heat dump on small gravity loop).
I found the details on
www.heatweb.com - I'm probably going to buy one of their cylinders. They show all sorts of options and this is what they suggest if the cylinder can't be gravity fed.
here's a direct link:
http://www.heatweb.com/xcelinstall.pdf
see page 18.
I thought this might be of interest as the document describes all manner of installations and would be of help with any setup not just ones involving their equipment.
I'm just wondering how easily I could hide the small gravity loop behind the stove - the neatest way of getting it all installed. If I boxed in behind the stove is plasterboard heat proof? (i.e. there's a lot of heat back there behind the boiler)...
still researching, and need to get some floors up...