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Posted by David Bonnell on February 22, 2007, 8:53 am
Hi all,
I've got two (heat exchanger) ducts running along the ceiling next to
a stringer in my basement. I want to move the ducts to the opposite
side of the stringer.
To place them there, the ducts would have to drop about 1' - 2' from
the ceiling to form a "U" around a set of 3' wide stairs. Aside from
the pains of moving ductwork, are there any reasons why this is a bad
idea? Condensation/moisture issues? Mismatched ducting?
Effective length of the ducts will not change by much...adding two 90
degree elbows will increase the length, but the ducts have less
distance to cover if they're on the opposite side of the stringer.
If anyone's interested in why I'd like to move 'em, it's because I'm
finishing my basement and height is an issue. By moving the ducts, I
get them out of my 'finished' area and open up the space a bit more.
Cheers,
Dave
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Posted by hawgeye on February 22, 2007, 10:16 am
"David Bonnell" wrote...
> I've got two (heat exchanger) ducts running along the ceiling next to
> a stringer in my basement. I want to move the ducts to the opposite
> side of the stringer.
>
> To place them there, the ducts would have to drop about 1' - 2' from
> the ceiling to form a "U" around a set of 3' wide stairs. Aside from
> the pains of moving ductwork, are there any reasons why this is a bad
> idea? Condensation/moisture issues? Mismatched ducting?
>
> Effective length of the ducts will not change by much...adding two 90
> degree elbows will increase the length, but the ducts have less
> distance to cover if they're on the opposite side of the stringer.
>
> If anyone's interested in why I'd like to move 'em, it's because I'm
> finishing my basement and height is an issue. By moving the ducts, I
> get them out of my 'finished' area and open up the space a bit more.
No offense Dave, but while I kind of understand what your describing, more
detail or a picture would be nice.
However, going by what you've given, you probably won't have
condensation/moisture problem unless you are moving the ducts to a much
colder area. As for the mismatched ducting, if the ducts are the supply and
return ducts for the same room/area, there shouldn't be a problem there.
Although you will be adding more restrictions to the airflow by adding
elbows to the air path. This may or may not result in a temperature
difference in the room/area of that the ducts are going to, which could
cause the entire system to be unbalanced.
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Posted by David Bonnell on February 22, 2007, 11:48 am
> No offense Dave, but while I kind of understand what your > describing, more
detail or a picture would be nice.
None taken, although I'm not sure I can describe it much better.
Since I can't attach a pic, I'll try some ascii diagrams...although
the chance of it showing up properly on your screen are small.
(You'll need to use a fixed-width font). Also, I'm going to change my
terminology a bit (I'll use 'beam' instead of 'stringer', since
"stringer" also refers to the support for stair treads.
There is a 6x10 beam (3 laminated 2x10s) running perpendicular to my
joists, and this basically splits my basement in half. Here's a top-
down view. The outer box represents my basement walls, and the "B"
vertical line running down the middle is the beam. The right side of
the beam will become the primary finished area. The "x"s mark the
existing path of the duct work.
Naturally, the beam is supporting the joists above it, and the beam
itself is supported by a few steel posts. There is a set of stairs on
the left, and the top of the stairs ("S") ends basically where the
beam is. As shown, my joists are running horizontally.
----------------------------------
| x x x x B x |
| B x |
| B x |
| B x |
| S S S S S S B x |
| S B x |
| S B x |
| S B x |
| S x x x B x |
| B |
----------------------------------
What I would like to do is move the ductwork to the opposite side of
the stringer:
Q
----------------------------------
| x x x x B |
| x B |
| x B |
| x B |
| S S S S S S B |
| S x B |
| S x B |
| S x B |
| S x x x B |
| B |
----------------------------------
P
In the current configuration (ducts on the right side of the beam),
the ducts are hung from the joists and are at the same elevation for
the entire length (i.e. no bends in the ductwork).
For the proposed configuration (second diagram, ducts on the left of
the beam), the stairs obstruct the ideal duct path (i.e. hanging
directly below the joists).
Here's a third, side view of the proposed move. The "J"s correspond
to joists, the ductwork is represented as "x"s. The duct forms a U-
shape to avoid the stairs. P and Q are just reference points seen in
the above diagram.
J J J J J J J J J J
P xxxxxxxx S S xxxxxxxxx Q
x S S S S S x
xxxxxxxxxxxxx
Ensuring I have a 'balanced' system is my biggest concern, as I am the
least familiar with that aspect of the system. I suppose a HVAC
expert is in order.
Cheers,
Dave
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Posted by hawgeye on February 23, 2007, 11:11 am
"David Bonnell" wrote...
>> No offense Dave, but while I kind of understand what your > describing,
>> more detail or a picture would be nice.
>
> None taken, although I'm not sure I can describe it much better.
> Since I can't attach a pic, I'll try some ascii diagrams...although
> the chance of it showing up properly on your screen are small.
> (You'll need to use a fixed-width font). Also, I'm going to change my
> terminology a bit (I'll use 'beam' instead of 'stringer', since
> "stringer" also refers to the support for stair treads.
> Ensuring I have a 'balanced' system is my biggest concern, as I am the
> least familiar with that aspect of the system. I suppose a HVAC
> expert is in order.
Dave, I'm not sure that helped much other than I think the ducts you are
referring to are your main supply and return ducts. That being the case,
then you could unbalance more than just one room or area, you would probably
unbalance everything that is down stream of the staircase that is opposite
of the air-handler unit.
Just out curiosity, where is the air handler unit located?
Having an unbalanced system is not the end of the world and can often be an
easy fix by adjusting a few dampers or adding a booster fan.
Having an HVAC expert wouldn't hurt, but you may discover your plan to move
the ducts may not be worth it as compared to just framing in the duct work
to finish the basement.
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Posted by David Bonnell on February 23, 2007, 2:11 pm
> Dave, I'm not sure that helped much other than I think the ducts you are
> referring to are your main supply and return ducts.
Well, I tried :)
> That being the case,
> then you could unbalance more than just one room or area, you would probably
> unbalance everything that is down stream of the staircase that is opposite
> of the air-handler unit.
> Just out curiosity, where is the air handler unit located?
Yes, these are the main supply and return ducts (they run parallel to
each other). The heat exchanger is located to the left of the beam
(along the wall at the top of the diagram). The supply/return ducts
run up over the beam, through the joists, then make a 90 degree turn
and follow the beam along its length until they eventually make
another 90 degree turn through the joists (back to the left side of
the beam) and proceed to the 1st/2nd floor of the house. It's tough
to show all of that detail in ascii!!
Dangerous thinking:
The length of either supply/return will not change by much (maybe a
foot or two), and the change in length will affect each duct in about
the same manner, so I wouldn't expect an imbalance (but I'm obviously
no expert). The only other concern would be a bit more airflow
resistance because of the addition of two 90 degree elbows.
> Having an unbalanced system is not the end of the world and can often be an
> easy fix by adjusting a few dampers or adding a booster fan.
> Having an HVAC expert wouldn't hurt, but you may discover your plan to move
> the ducts may not be worth it as compared to just framing in the duct work
> to finish the basement.
You may be right, but I'm hopeful that I can move the ductwork. If
not, it's not a dealbreaker, but more of an annoyance. In any case, I
think a residential HVAC expert is in order. While I might be
comfortable moving the ducts by myself, I'm not too comfortable with
potentially screwing up my air quality.
Cheers,
Dave
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