Mike Rocket J. Squirrel Elliott wrote:
On 12/21/2004 10:33 PM George E. Cawthon wrote:
Mike Rocket J. Squirrel Elliott wrote:
On 12/21/2004 6:35 PM HvacTech2 wrote:
Hi Mike, hope you are having a nice day
On 20-Dec-04 At About 09:05:02, Mike Rocket J. Squirrel Elliott
wrote to All
Subject: Turbine in my furnace?
MRJSE From: "Mike Rocket J. Squirrel Elliott"
MRJSE j.michael.elliottAT@REMOVETHEOBVIOUSad elphiaDOT.net
MRJSE So what's the point of the inducer blower? Never had one on
any other
MRJSE natural gas forced-air furnace I've lived with.
To put it simply it increases the efficiency. it allows for more heat
exchamger so you can wring out more heat before it goes up the chimney.
Okay -- it would be interesting to see the difference between
"passive" and inducer-blown heat exchangers.
I'd really like to reduce the noise output of the furnace. The burner
gets its air for combustion though the louved door, which also allows
the sound of the inducer blower to fill the house with its loud
whine. The exhaust from the inducer blower -- the combustion product
-- is vented out of the closet through a 5'' diameter steel pipe
chimney to someplace I have not yet noticed, probably up on the roof.
Clearly I cannot replace the louvered door with a solid door, as it
would seal the closet and provide no place to pull air from for
combustion. I could put on a solid door with a small opening --
probably would not need to be any larger in cross-section than the
exhaust pipe (about 16 square inches), but that would still leave a
path for inducer blower sound to exit the furnace closet.
Something else: since the inducer blower sends exhaust out of the the
house, then replacement air must enter the house through cracks and
other openings. This does not contribute to overall efficiency.
So it might make sense to provide an combustion intake opening to the
furnace closet that comes from the outdoors. Outside air gets sucked
into the closet, through the combustion chamber/heat exchanger, and
blown up the chimney by the inducer blower. As mentioned in another
fork on this thread, the furnace is in a closet which sits on a
concrete slab. It does not share a wall with the outdoors. Since I
don't have direct access to the outdoors from the closet, how about
using a solid door and running something like dryer exhaust tubing
from outside to provide air for combustion?
The closet has a ceiling right? Is the ceiling the floor to an
attic? If so you can get the air for the furnace from the attic,
install a solid door, and even install some sound insulation.
Alas, the furnace closet is on the ground floor of a two-story house.
The furnace chimney does not have a straight-shot up to the roof, but
instead takes a turn as it exits the ceiling of the closet and heads
upwards through some convoluted path I am unable to see. MUADIB's idea
of a coaxial three-wall chimney to both blow and suck through will be
tough to make work in this situation. Far easier would be to cut a hole
in the side of the closet and run an intake through the laundry room
above the washer/dryer to the rear of the house.
I suggest that you find out what manufacturer states is needed for the
air supply (hint--it will be a lot more than the 5" exhaust).
I've been thinking about that. The inducer blower forces combustion
products and heated air up the chimney. This creates negative pressure
in the closet, so air gets sucked in through whatever opening there is
in the closet for fresh air to come in. In my case, the
sound-transparent louvered door. Since the exhaust products are hot, it
seems to me that for every cubic foot of cold air that comes in, a
larger volume of hot stuff goes out, since gases expand when heated
(thus hot air balloons). So the intake could be smaller than the output
-- unless we want as little resistance for the inducer to have to suck
against. That blower may be much better at blowing than sucking.
In fact, you will need two air supplies for the closet--one at the
ceiling and one at the floor. Not a problem, since both can come from
the attic.
Two? Is this counting the house air which is heated and blown throughout
the house through the ducts?
Get the installation manual from the manufacturer of the furnace.
Manuals are good for telling what should be done. But not why. That's
the realm of smart guys that study these things.
Two, yes, and not it doesn't have anything to do with the
air blown throughout the house (that comes from the cold air
returns). The lower one is for the combustion air. The
upper is for ventilation (a safety feature). I believe each
is supposed to be 1 sq inch for each 1000 BTU but not less
than 100 sq inches. Too bad about the concrete slab,
sounds like a PITA. Never lived in a house built on a slab,
glad about that too.
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