I have a Goodman 90+ furnace with a 3" PVC output pipe, which ends in
Here's a side view, with W being the wall:
I've always thought that it makes more noise than it should when the
furnace is on. It's sounds like a steam pipe at a factory.
If I were to compare it to anything, I'd say it is 3 - 4 times louder
than my AC compressor.
Is that normal?
Goodman eh? LOL. They do make some noise. I'd say mine is 50 times
louder than my a/c unit. My a/c unit is very very quiet. I'd say
standing right next to the exhaust/intake is about the same as say a
household vacuum at 50 feet.
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I don't think my Goodman is anywhere near as loud as a vacuum, nor
is it as loud as the AC/heat pump. The AC/heat pump (Amana) isn't
that noisy, but the frequency of the noise is different. The
exhaust/intake of the furnace has more high frequency components.
All that said, I have an air induced water heater with an exhaust
about 10' from the furnace intake/exhaust and it is by far more
noisy than the furnace or AC/heat pump and it runs in the summer
when you are outside. Not only is it noisy outside, it is real
noisy in the basement. I hate it. But, the central vac outside
vent beats them all. I probably should put a muffler on it.
Interesting. Does it seem the noise is the vent fan? Or turbulence
noise in the pipe? You possibly could use a larger pipe to reduce the
air speed. High eff furnaces condense at the unit so slowing the vent
gas speed should not matter. If it's fan noise then you'd have to
play around with the fan it's self to reduce the noise.
Well it would be a bit of an experiment and depend on how complicated
your pipe run is. Increasing from 3" to 4" almost doubles the area.
From 7 sq in to 12.5 sq in. 6" pipe (I'm pretty sure there is not
any 5") is 4 times the area of the 3". But pvc pipe is not real cheap
in these sizes so if you have a straight run that is easily accessed
it might be worth the experiment but otherwise I don't know. And keep
in mind it is an experiment.
Mine is noisy, but I had no need to quiet it. Resonances can make
and sharp exit point will make it worse. You can put a muffler on it.
Why vertical T ?
Odd thing people do. Put your hand over the top exit and see if
it improves sound. A muffler is made with a larger pipe, preferably
with a bend, with a lining of fiberglass
around the perimeter then a reduction in pipe size. You want the exit
to be smaller
than the main pipe size. You have TWICE the exit size as your main
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