Using dryer with rigid duct and 3" outdoor vent
 

The previous owner of my house had put in a 3" dryer outdoor vent. Why
I don't know, perhaps this was the size years ago, but in any event I
thought I would compensate for this by running all rigid duct from my
dryer to the vent. I ran about 8 feet of 4" duct with 2 elbows: one at
the dryer outlet in the back, and one at a 45 where the duct meets
the outdoor vent. Then there is a 4"-3" adapter at the outdoor vent.
Being the fact that I ran all smooth duct, is this enough to
compensate for the 3" opening to the outside, or do I still need to
get a 4" vent?

Using dryer with rigid duct and 3" outdoor vent
 

On Tue, 6 Jan 2009 04:47:13 -0800 (PST), Mikepier
wrote:

The previous owner of my house had put in a 3" dryer outdoor vent. Why
I don't know, perhaps this was the size years ago, but in any event I
thought I would compensate for this by running all rigid duct from my
dryer to the vent. I ran about 8 feet of 4" duct with 2 elbows: one at
the dryer outlet in the back, and one at a 45 where the duct meets
the outdoor vent. Then there is a 4"-3" adapter at the outdoor vent.
Being the fact that I ran all smooth duct, is this enough to
compensate for the 3" opening to the outside, or do I still need to
get a 4" vent?

I don't know the specs for your drier. They vary so what is
OK with one might not be OK with another. I suspect you will be OK
but remember that by providing that 4" vent you will reduce back
pressure and that will mean faster drying, and longer drier fan life.
Over all I would want the 4 Inch vent.

Using dryer with rigid duct and 3" outdoor vent
 

On Jan 6, 7:47*am, Mikepier wrote:
The previous owner of my house had put in a 3" dryer outdoor vent. Why
I don't know, perhaps this was the size years ago, but in any event I
thought I would compensate for this by running all rigid duct from my
dryer to the vent. I ran about 8 feet of 4" duct with 2 elbows: one at
the dryer outlet in the back, and one at a 45 *where the duct meets
the outdoor vent. Then there is a 4"-3" adapter at the outdoor vent.
Being the fact that I ran all smooth duct, is this enough to
compensate for the 3" opening to the outside, or do I still need to
get a 4" vent?

If it will make you sleep more soundly at night, get the bigger vent.
Otherwise quit overanalyzing things and do your laundry.

Using dryer with rigid duct and 3" outdoor vent
 

"Mikepier" wrote in message
...
The previous owner of my house had put in a 3" dryer outdoor vent. Why
I don't know, perhaps this was the size years ago, but in any event I
thought I would compensate for this by running all rigid duct from my
dryer to the vent. I ran about 8 feet of 4" duct with 2 elbows: one at
the dryer outlet in the back, and one at a 45 where the duct meets
the outdoor vent. Then there is a 4"-3" adapter at the outdoor vent.
Being the fact that I ran all smooth duct, is this enough to
compensate for the 3" opening to the outside, or do I still need to
get a 4" vent?



*That little 3" vent is enough to cause resistance in the air flow. Give
the factory a call and see what they say, but I say 4" all the way.

Using dryer with rigid duct and 3" outdoor vent
 

I checked GE online for the specs on my dryer. Although this is not
the exact model of mine (about 8 years old), it is equivelant. On page
2 shows the max duct length chart. Notice how there is a column for 4"
cap and another for 2 1/2" cap. Does this mean since I'm using only 8
feet rigid duct w/2 elbows it should be fine? Or is this chart
misleading.
http://products.geappliances.com/Mar...223gg_r 3.pdf

Using dryer with rigid duct and 3" outdoor vent
 

Mikepier wrote:
I checked GE online for the specs on my dryer. Although this is not
the exact model of mine (about 8 years old), it is equivelant. On page
2 shows the max duct length chart. Notice how there is a column for 4"
cap and another for 2 1/2" cap. Does this mean since I'm using only 8
feet rigid duct w/2 elbows it should be fine? Or is this chart
misleading.
http://products.geappliances.com/Mar...223gg_r 3.pdf

Dunno. I've got thirty feet of 4" PVC ducting (I guess you'd call that
'rigid') with six elbows (2 are 45°) and my dryer does what it's supposed to
do. 'Course the dryer is 15 years old and the ducting has been in place for
only two years (previously it dumped into the attic! Goddamn roofers), so
maybe the whole shebang will deteriorate over time...

Using dryer with rigid duct and 3" outdoor vent
 

"Mikepier" wrote in message
...
I checked GE online for the specs on my dryer. Although this is not
the exact model of mine (about 8 years old), it is equivelant. On page
2 shows the max duct length chart. Notice how there is a column for 4"
cap and another for 2 1/2" cap. Does this mean since I'm using only 8
feet rigid duct w/2 elbows it should be fine? Or is this chart
misleading.
http://products.geappliances.com/Mar...223gg_r 3.pdf



*That 2.5" opening is the flap on the vent opening, not the duct diameter.

Using dryer with rigid duct and 3" outdoor vent
 

On Jan 6, 1:46*pm, "John Grabowski" wrote:
*That 2.5" opening is the flap on the vent opening, not the duct diameter..


Seems odd they would make a 4" dryer vent with only a 2.5" flap. What
is the purpose of that?

Using dryer with rigid duct and 3" outdoor vent
 

On Tue, 6 Jan 2009 04:47:13 -0800 (PST), Mikepier
wrote:

The previous owner of my house had put in a 3" dryer outdoor vent. Why
I don't know, perhaps this was the size years ago, but in any event I
thought I would compensate for this by running all rigid duct from my
dryer to the vent. I ran about 8 feet of 4" duct with 2 elbows: one at
the dryer outlet in the back, and one at a 45 where the duct meets
the outdoor vent. Then there is a 4"-3" adapter at the outdoor vent.
Being the fact that I ran all smooth duct, is this enough to
compensate for the 3" opening to the outside, or do I still need to
get a 4" vent?

You'll get better air movement with a 4" vent. I was not aware there
are 3" dryer vents, but I've seen plenty of 6" vents.

Using dryer with rigid duct and 3" outdoor vent
 

"Mikepier" wrote in message
...
On Jan 6, 1:46 pm, "John Grabowski" wrote:
*That 2.5" opening is the flap on the vent opening, not the duct diameter.


Seems odd they would make a 4" dryer vent with only a 2.5" flap. What
is the purpose of that?



*You are looking at it wrong. The flap swings open 2.5". The actual opening
area is much greater. It might be 2.5 inches by 4.25 inches wide.

Using dryer with rigid duct and 3" outdoor vent
 

On Tue, 6 Jan 2009 04:47:13 -0800 (PST), Mikepier
wrote:

The previous owner of my house had put in a 3" dryer outdoor vent. Why
I don't know, perhaps this was the size years ago, but in any event I
thought I would compensate for this by running all rigid duct from my
dryer to the vent. I ran about 8 feet of 4" duct with 2 elbows: one at
the dryer outlet in the back, and one at a 45 where the duct meets
the outdoor vent. Then there is a 4"-3" adapter at the outdoor vent.
Being the fact that I ran all smooth duct, is this enough to
compensate for the 3" opening to the outside, or do I still need to
get a 4" vent?


From a fluidics standpoint, the cross sectional area is proportional
to the airflow. So,

area = Pi*r^2
area (of 3") = 7.06
area (of 4") = 12.5

A 77% more flow in 4" compared to 3".

Reducers, turns, smoothness, length, pipe size, lint buildup all
effect airflow.

Using dryer with rigid duct and 3" outdoor vent
 

Looks like I'll be changing it to a 4" duct soon. It's not that hard,
I just have to make the 3" hole now 4".

Using dryer with rigid duct and 3" outdoor vent
 

On Jan 6, 9:16*pm, Mikepier wrote:
Looks like I'll be changing it to a 4" duct soon. It's not that hard,
I just have to make the 3" hole now 4".

I changed it over the weekend, and it seems dryer performance has
improved.