On Fri, 29 Apr 2011 11:21:02 +0100 Fred wrote :
I couldn't see any mention of non return valves in the boiler flows,
I'd have thought they'd be essential for single running.

In theory you need them to stop reverse circulation, but the resistance
of the 1.5m 42mm shunt pipe (aka low loss header) is next to nothing
compared with the 22mm pipes back to the other boiler, its internal pump
and its heat exchanger.

--
Tony Bryer, Greentram: 'Software to build on' Melbourne, Australia
www.superbeam.co.uk www.eurobeam.co.uk www.greentram.com