On Sat, 08 May 2010 09:36:46 +0100, Theo Markettos wrote:

YAPH wrote:

The sensible energy-efficient approach is to replace the inefficient
and potentially-unsafe open-flued boiler with a high-efficiency
room-sealed one.

This isn't practical in this situation, much though it's obviously the
best option.

It will be necessary in due course when the existing unit packs up.

The main thing is to reduce draughts while not interfering with
combustion. Does such an arrangement draw in cold air by convection? So
would, for example, a louvred path be OK because the combustion causes
lower pressure in the room that would suck in fresh air? Or would the
boiler happily churn out CO before it causes a significant pressure
difference?

The important criterion is that the air vent be unobstructed by e.g. fly
grilles. Commercially-available vents for the inside wall generally have
louvres, but that won't do much to help if there's a stiff breeze blowing.
A properly installed appliance should have its air supply arranged so as
*not* to produce an unpleasant draught across living areas, e.g. by being
ducted under the floor to come up beside the appliance (precisely because
it may encourage occupants to block it up) but this is only a
recommendation rather than a requirement of the British Standard and more
honoured in the breach.

I'm a bit puzzled by the units. That means a grille 7cm x 5cm,
presumably? But what's the amount of air input you need to the boiler
(ie in cm^3 per second)?

The free area of ventilation is what's specified in the gas installation
regs. The volume rate is something you (or someone else with a better
recollection of school physics & chemistry than me :-)) can work out.



--
John Stumbles -- http://yaph.co.uk

I've got nothing against racists - I just wouldn't want my daughter to marry one