Look for dampers where the ducts begin or attach to the plenum. This is
where I put dampers when I put in some new runs for my basement. The start
collars are predrilled for the dampers already.
If you have exposed ducts in your attic or basement/ crawlspace then look
for crushed or sagging ducts that have come apart at the joint(s).
We don't have an attic or basement and the plenum just goes into
the wall. We have a crawlspace under the stairs and lower landing
but there obvious signs. The house is 50 years old. My next door
neighbour has the identical problem. We've asked people who do
duct cleaning if they can solve the problems but we've come up
This is Turtle.
You don't need a rebot to crawl duct because a good hvac man can size ducts
from the outside and see baffles if you have them from the outside of
ductwork. 90% of the time when a poster here says what you just said. the
ductwork is jusy plainly too small but not being too bold 10% of the time it
might be a problem like stopped up duct or a problem of some kind.
You start is to get a hvac man to run a manual D on your system and see if
it is the right size.
There are no visible ducts as we have no attic or basement in which to
The air roars through in some of the rooms, whilst in others you can barely
feel or hear it. The house is about 50 years old and my next door neighbour
has the same problem, although there are some differences in the layout
of their ducts.
Do you mean "manual diagnostic" ?? Size can't be changed easily.
Then you need an HVAC guy with a tool called the Inspector...its an infrared
TV cam that is used mainly for checking for cracked heat exchangers..
However, if you find one, do not expect the check to be cheap.....about
$150...those units cost an arm..
No..he means a ACCA Manual D duct size calculation....
First you need a room by room manual J, that gives you the total number of
BTU per room, and then, knowing your states code on CFM and Face Velocity,
at return, you need to find out static presure of the system, total, and
then, determine the size of the duct, using the ACCA Ductulator, and Manual
D, making sure you do not exceed velocity as stated by your states local
code, or the International Mechanical Code...
I charge $200 on a retrofit or new install for this...and the reason is, its
time consuming...you need about $300 just in manuals, and the online crap
that is out there is normally wrong.
If you have never done one, but have the books, its almost guaranteed that
your first 10 to 15 will be wrong....we go to class on it yearly...its
changing that much.
this is Turtle.
1) You was speaking of finding baffles , dampers, and other item in the
ducts that is stopping the air. I don't need to see the outside or inside of
the duct to know that it is there. I have equipment and tools that will tell
me it is there along with the Maunul D data. I don't have to see something
to know it is there. this is the reason we get the so called big bucks to do
this type of work.
2) A system of ducts can be too big and cause the same problem like too
small. A lot of people will just live with these problems for thinking it is
too hard to or costly to correct problem like this. I have corrected systems
like this by just installing a push baffle in it to change the air flow and
not change the duct system at all. It can be little as a $4.00 baffle to a
complete rework of the ducting system. It is most of the time be just a few
minor changes to fix them.
3) If you hear roar , whisles, and little or no air out other vents sound
like a OVER sizing problem to me or the ducts are too big and have to be
restricted. Now i can't see it from here but this is what i think. Now if it
is over sizing problem. I can fix them for about $150.00 including all
equipment and labor. I have fix one for my friend with 2 bath towls and a
manual D data. I would restrict air till my flow meter said the air flow was
right out each of the registers.
Sounds reasonable, do you want to do a call in Toronto, Canada? (I guess
you're in Louisiana, from your server address), perhaps you can recommend
someone up here ?
Give me the link (by email if you prefer) to download "Manual D". As to whether
it's 'over my head' or not, is immaterial, as you have no knowledge of my
background. In fact I worked, 10 years ago, at the University of Toronto,
Dept. of Physics, Atmospheric Physics Group on mathematical modeling
of closed-loop wind tunnel systems (wind tunnels that simulated a falling
air particle, and the growth of ice crystals) and may know a lot more than
what you presume.
Just because the data is fed into a computer, doesn't mean its impossible
to understand (not to belittle your knowledge and training).
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