On Wed, 25 May 2005 01:21:43 +0100, Fergie
wrote:

"Dave Liquorice" wrote:

On Tue, 24 May 2005 22:54:19 +0100, Fergie wrote:

A leak inside a room sealed appliance would not generate a gas
smell inside the house, but outside at the flue terminal.

Could you explain for the thickies just how this is possible?

A "room sealed appliance" is just that, it is sealed from the room.
Nothing on the inside can get into the room, air comes in and exhaust
goes out through the balanced flue. SO the only place you'd smell a
gas leak in the appliance is outside at the flue.

Hmm, so room sealed appliance is a different concept to room sealed
flue then?


No. The flue is part of the means to make a room sealed appliance,
well, room sealed. It consists either of some concentric or side by
side system of pipes or ducts which are used to feed in the combustion
air as well as to feed out the combustion products.

On older RS boilers, this is usually done by natural draught, whereas
newer ones normally have a fan and can consequently have a smaller
flue.

The other aspect is that the case of the boiler is sealed inside the
house so that no air can enter or anything escape. Better designs
are arranged, when the fan is running, to have slightly negative
pressure relative to atmosphere in the case so that if there is a
slightly imperfect case seal, there will be a net inflow of air rather
than possible escape of fumes.

Condensing boilers need a means on the case of the boiler to provide
an outlet for the condensate. This is achieved by having a small
water trap.



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