On Jan 7, 2:20*pm, Jules Richardson
wrote:
On Thu, 06 Jan 2011 23:11:44 -0800, harry wrote:
We don't have "furnaces" that need to bring cold air into the house.
It defeats the purpose.

Hmm, the last place I lived at in the UK had gas-fired CH; where do
such heaters typically source their combustion air from, then? I'm
reasonably sure that one took air from outside and then burped it back
into the outside world, just like a typical US forced-air furnace does..
It was, however, mounted on an external wall, so there wasn't a long
pipe run within the house for the combusion air; typical US furnaces
I've seen have been in a more central location within the home.

Air is drawn from the outside directly into the (gas) boiler, so it
doesn't have to enter the room at all. Sometimes it has a co-axial
sytem, ie combustion gases exit the centre pipe and air is drawn in the
annular space between the two pipes. This preheats the air also.
Sometimes there are two separate pipes. The boiler is, if possible,
mounted on an exterior wall but they are available with pipe(s) up to
25m long.

Right.... so how's that any different to a US furnace which may have a
pipe supplying combustion air from the outside world, or be mounted
against an exterior wall and thus draw air directly into the furnace?

I'm just trying to understand: "We don't have furnaces that need to bring
cold air into the house", because it seems to me that the combustion side
of things is the same, so there's no logic in saying (just from that
aspect) *that one is any better than the other - no matter which side of
the Pond you are, the system will draw cold air from outside, and may or
may not do so via a pipe. I hate forced-air systems*, I really do, but
purely on the "bit that gets hot" side of things I'm not sure that a CH
boiler is really any different.

* I can see the benefits if you're in a climate that also needs AC - but
for everywhere else it seems a bulky and inefficient way of getting heat
to where it's needed the most.

(In the early '80s I was in a house in the UK that had forced-air, but
all the others I lived in over there were CH/rads. Current place in the
US is a combination of forced-air and electric baseboard)

cheers

Jules- Hide quoted text -

- Show quoted text -

If you draw (cold) combustion air into the building, it makes that
building colder. Even if it's just the basement, the house is sitting
on a cold room.
The air needs to go straight into the "furnace" not into any part of
the building first.