On Mon, 01 Oct 2012 16:24:27 +0200, Martin wrote:

The chap who told me tested it and said it was 85% efficient as at
last week.

Interesting. How did he measure the efficiency?

Normally by measuring the temperature of the flue gases. The cooler they
are the more heat has been taken out of them on passage through the
boiler.

I've been thinking about piping from the flue to the greenhouse to
utilise that wasted 15% of the heat.

Mind you don't gas those in the greenhouse

The plants won't mind the warmth and CO2, might have to keep an eye on
the humidity.

--
Cheers
Dave.