I have a forced air heating system in home, but one of my rooms upstairs is
preaty cold in winter. I tried adjusting dampers in ducts and
closing/opening heat registers, but nothing really works. Now I am
considering installing duct booster fan. There are types that goes inside
duct (inline) and other that goes on top of the register. Anyone had
experience with these things and could recommend which thype to use? Reviews
on google shows that common problems with them are:
2. Not as powerfull as most expected.
I would need something that would be easy to install, quite and powerfull
enough for big room.
Any recommendations would be really appreciated.
I have to wonder is there is a flaw in the system. Blower at proper speed?
Duct sizing proper?
A duct fan still may be the cheapest fix short term, but it may be good to
look at other alternatives too.
I have new Carrier infinity system installed this year. Continous fan is
running all the time and mixes air in the house.
I cannot change blower speed as it is controlled by furnace. It is two stage
furnace, and I did noticed that when furnace is working at higher BTU
output, blower also works louder and there is much more air comming into
that room. But normally, when furnace operates at lower output, you can
bearly feel air comming out of heat register. I am going to read if I can
change blower speed during low output operation, but I do not believe this
is a case.
Duct sizing - even if it is a problem, it would cost too much to tear walls,
floors and ceilings to change that.
Blockage? Maybe. How do I test that? Air is comming in when furnace blower
operates at highest speed. I did try to put in snake (used usually in
plumbing) into register, but could not see anything.
It looks like that this room is too far from furnace, it has at least 3 90
degree angles and that might be a problem.
Any help is appreciated.
Another thing to check for is return air capability. In order for air to
flow into the room from the duct, the same amount of air must flow out of
the room and back to the furnace. Make sure doors are open and cold air
returns are not blocked.
To what degree? Forced hot air heating was retrofitted to this old
house. The return duct (12x24) sits behind my TV stand. Due to the
size of the TV itself the cabinet is 10 inches out from the wall.
Should that be enough?
This is Turtle.
There is no easy fixes in the hvac ducting system problems.
Now my opinion here on Duct fans. Useless and noisey. I know of no customer that
was satisfied with a duct fan as to getting enough air to a room.
The only true fix is to get a hvac company to come redo that duct to get more
air or what you need to go to that room. This is the cure and everything else is
nothing but wishful thinking.
This is Turtle.
You hit on something that was brought up at a rheem school on duct fans. Duct
fans can slow the air down if the Cubic feet per minute is above the cubic feet
per minute of the duct fan. It will act as a block to any air flowing above the
rating of the fan's C.F.M. rating.
if you need 200 CFM for the duct size and you get a fan rated for 150 CFM . the
air flow will only be 150 CFM and block the other 50 CFM that should have flowed
Your point here is a very good one.
I agree with Turtle.
I did try a couple in my home . . yea I knew better, but I tried anyway.
One helped, but did not really resolve the situation. Due to some unique
situations it did not cause any noise or vibration problems and did bring
the room temp to bearable, but not right. The other did cause noise and
offered no noticeable improvement.
Someday I will be doing some serious HVAC works and those two problems
will be addressed properly.
I had a similar problem, but with cooling, not heating. The last run
that goes to an upstairs bedroom is at the end of the duct run. They
used small round ducts to run from the end of the rectangular duct in
the basement to go to the second story bedroom, which is a long way,
as it's a large home. There is no cost effective way to add or
expand the existing duct work.
So, I added one of the squirrel cage booster blowers near the end of
the rectangular duct, just before the round duct branchs that go to
the second story. It's the type that use a cutout in the bottom of
the duct and part of the blower then sits inside. While it's not a
cure all, it has definitely helped a moderate amount. I tried holding
paper over the registers with it on and off and can see a noticeable
difference and it's definitely cooler in the summer, though still not
Since I only had a problem with cooling, I also wired it up to the
furnace blower with a switch, so that I can shut it off in winter, as
I didn't want to pump extra heat where I don't need it.
I'm surprised there aren't more solutions to this problem available.
For example, if they had a blower unit that was rectangular, the size
of the duct, and could replace a cut out section, one would think that
would be a higher performance solution. Of course, we all know the
right answer is it should have been done right to begin with, but it's
too late for that.
A long run with a 3- 90 angles will make flow less than optimum.
Replacing that run and insulating will do alot. I just insulated my
ducts and the 1 cold room is now more even to the others. You may
slightly reduce other vents flow but it can harm the furnace. Proper
ducting is best, a fan may or may not help. How is attic insulation,
that would be an easy way to boost overall efficiency and perhaps help
your cold room the most.
Call the expert and balance the system.
I had to redo some duct work to solve the problem like yours.
My son's upstairs bedroom is farthest from furnace and was always
cold in the winter. Had to call furnace guy. It is OK now.
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