That's where I am too. As I said, one advantage to being
a little bigger is that you can heat the house up faster.
I can go up about 6 deg an hour. That way if you don't
always come home at the same time, you can have it
set back and recover faster.
have more, but I
Where is that set? Sounds like at the furnace and you
don't have a two stage thermostat? Ideally the thermostat
should make the selection because it knows what the
temp is and where it needs to go.
Well, it must be an odd thermostat, because every one
I've ever seen had it. What about AC? What does it do
with AC on, or haven't you had a day where you could
try it? On heat the blower should move around 900 -1200
cfm. On fan only typical would be maybe 1400. On AC, 1800-2000.
I'm going to assume it is temp, and not air
quoted text -
I don't see how the reputation of the HVAC company is
a factor. The blowers are what the blowers are. It's not
like Rheem is 2000 cfm and Trane is 800. For the same
size furnace they are about the same. And going from say
a 75K furnace to 110K, doesn't change it all that much
either. It is possible that they moved something slightly,
or didn't put screws, hangers back where they should
be. But I assume the noise isn't near the furnace, right?
You should have a pretty good idea if it's temp or air pressure. You
can hear the blower ramp up. If the noise occurs in the first 30 secs
or so, it;s likely air pressure,
because it's going to take longer than that to heat it
up. Also, the bangs I've heard from air pressure occur
both when it starts up and when it shuts off. Does it
bang right when the blower stops?
Lots of good points, trader4. Btw, I'm from around cherry hill. Now,
The time between the first and second stage is set at the dip switches
in the furnace, not the thermostat.
I do have a setting for fan only, but nothing turns on when I set it.
Time to read the manual, I guess.
I didn't start the AC yet, too cold for that.
I assumed a good hvac company would not sell me something if they knew
the ducts couldn't handle it.
No, the noise is not at the furnace, it is at one of the ducts that is
farthest from the furnace, and another that is about half that
distance from the furnace. No noise at the closest ducts. I assume
pressure would get those first.
The first bang is well after the start of the ramp up. And I get
several bangs long after it stops, never immediately after it stops.
Remember too that I was able to get rid of the start up bangs by using
heavy duty tape to hold the duct open so to speak.
Thanks for all your help, btw.
Trader4, I just figured out how to get fan only, and after 5 minutes,
no noise. So I guess that clinches it, it's temp and not noise, and I
can fix it by getting at least the last foot or so of the duct
replaced or strengthened. My confusion on this temp vs pressure issue
started because I have the setting at 71/69, and that seems too low to
cause the duct to expand and make the REALLY POWERFUL BANG. But then,
when I hold my hand to the vent, the air pressure seems pretty low
Thanks for everything. I really hope the home improvement guy gets
this fixed. I'm going nuts from this noise.
But the temp in that duct is swinging from 70 to 110 or so, which
is plenty to cause enough expansion/contraction. If it runs through
any colder areas, it could be even more swing.
It should be easy to fix once you have the wall opened up. It sucks
though that you have to do that. Here's a thought. You might want to
do the opening up part yourself. If you do it, you could open one or
two smaller openings where you think the problem is. If you can
see it, you might be able to figure out how to shove something in
to support it, etc without tearing out a whole wall or ceiling worth
It's the ceiling, not the wall, and I expect the home improvement guy
will just tear out a small strip to reveal the duct. I imagine I just
need a strip of about 1 foot by 3 feet. But we'll see. I'll do
anything to get this fixed. I don't see that the whole ceiling needs
to come down.
I don't know how you're paying the guy, for the job, by
the hour, etc. But for something like this, if you can
do the opening up, fiddling around yourself, you might
save $$ and have a better result. Like I'm thinking the
guy opens up one spot. Then you have to cycle the
heat so you can see if it moves. Maybe you can't
see it that well, did it really move or not, etc. Now
you have to wait for it to cool, cycle it again. Then
maybe open up another spot or bigger spot, etc. And
if you think you have it fixed, I'd want to wait at least
a day or two to make sure before closing it. If you
open it and do the fiddling around, it might be better.
The preferred way is to have a two stage thermostat
that makes the selection. In some cases, it may be too difficult
to do it that way because it takes one more
wire from furnace to thermostat. If an extra wire isn't
there and it's not easy to run, then you use the fallback
mode of letting the furnace do it.
The advantage is the thermostat knows that if it's
60 and we're going to 70, then we want 2nd stage
right away. Conversely, if it's been running for 11
minutes and it's only .5 deg to go, no sense in going
to 2nd stage.
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