On 28 July, 09:06, "Dave Liquorice"
wrote:
On Wed, 28 Jul 2010 07:26:19 +0100, Grimly Curmudgeon wrote:
You don't need two of anything. Just the one would do,

I can't get me 'ed around the requirement for four and then dragging
the HW circuit into the equation. I guess there could be a second
loop from the wood burner to a coil in the HW cylinder...

As for spring valves I doubt very much that gravity would have enough
'umph to open them. A biased open(*) flap valve that closes when the
pump for the oil boiler tries to cause flow through the woodburner
loop might work.

But still doesn't avoid the problem of no flow through the
woodburner. At least with only one valve the woddburner boiler would
still be open but could still boil, Maybe adding another vent
vertically close to the woodburner with a whistle on the end... B-)

(*) By orientating it so gravity makes it open.

--
Cheers
Dave.

Our woodburner in a similar set up has a motorised valve and pump on
the pipe that links the woodburner's boiler to the main heating loop
and these are controlled by a thermostat on the flow pipe by the
burner. For safety reasons that are two radiators that are directly
linked to the woodburner to dissipate any excess heat.

Jonathan