"John Stumbles" wrote in message
...
On Fri, 06 Jun 2008 20:23:58 +0100, Heliotrope Smith wrote:

"Ed Sirett" wrote in message

That will be a slight over estimate. Pretty much all appliances are
quoted in gross. So 9 and 18 are the figures. Also the combustion air
supply is required to the room containing the compartment. This is
4.5cm2/
kW (from outside air), but the first 7kW are discounted.

Not an estimate, but the figures stated in the regulations.
I did add in my post that the figures are net so of course divide 1.11
if
input is stated gross to give the required size of vents.
You are a little out of date with combustion air supply sizing. This has
been 5cm2 per kW (-7kW) for some time now.

which, funnily enough, gets you to 4.5 cm^2

You're right. Too much red stuff, should have realised ED was talking in old
money.