peter wrote:
I have several rooms in my house that I don't have to use, so I close them
off and shut off the heater registers in those rooms to save energy.
However, this causes the remaining registers to become very windy and noisy.
I believe the reduction in air flow also increases the furnace output
temperature and therefore increases heat loss while the air is traveling in
the heating ducts in the crawlspace. Also air is lost due to leakages in the
heating ducts -- my crawlspace is warmer than outside by at least 10
degrees.

Is it generally possible to lower the heat output of a furnace? This is what
I have (replaced last year):

http://216.122.22.11/FetchDocument.a...3-559b84978136

I see three burners inside. I can either pull out one of the burner, or use
the shut-off valve to reduce the gas supply. I imagine removing one burner
would be more efficient since the remaining two burners will operate at
their designed setting.

But I'm not so sure the blower speed can be change. I don't mind rewiring
anything if I know it can be done.

You could change pulleys on blower/motor, but it'd probably be simpler
to identify
the registers that are, in effect, whistles and replace them. Assuming
that you're not
trying to force too much flow through them- too much fan/too few
register sq-ft.

Like, if your system had x registers with, say 20 ft/sec flow through
them, and you
now have x/3 of the same registers, you'd have wind tunnels. You don't
want to
radically reduce the discharge area, and maybe want to consult with
local experts.

One thing that might help right now, is to lower the fan-switch setting
on the
furnace, so the fan comes on at lower temp. (And shuts off at lower
temp also.) This
will reduce temp of ducting, obviously, and boost efficiency of unit.

Some registers I've seen tend to whistle when almost closed. You may
want to
open some up a bit. Or replace with quieter.

J