Duct Shapes

[hopeful100]

Hi

1) Why we prefer that duct shapes should be square?

2) Whats the difference between circular shaped ducts and square shaped ducts , i mean where we will prefer circular shape and where we will prefer square shape ducts?

[fearlessfurnace]

square shapes fit over ceilings and match up with square equipment better. they are easier to hook different sizes together. round would be more efficient in every way if it would fit.

[flange]

Rectangular shaped ducts have a way of being easy to layout and install as opposed to round or oval. As noted, above ceiling is a consideration on any project, especially larger commercial jobs requiring lots of airflow. Every trade knows that there will be a duct somewhere that they have to miss with their pipe, wire whatever.

In commercial real estate, area of the occupied space is treated like gold, so ceiling heights, mechanical room sizes etc all come in to play in calculations of rent, utilities etc in terms of price per square foot.

[AlmondEyes]

Round duct is a pain in the butt if it gets squooshed a bit at the shop, on the truck, or hanging around the job site before it gets installed. Rectangular duct is stronger.

[doubleduece]

I ditto everthing except
Rectangular duct is stronger.

Double wall spiral duct is pretty stout also.

[AlmondEyes]

I never installed double wall spiral, so I'm ignorant about it...

Round duct is also easier to take apart to clean or replace than rectangular would be, such as from an oil burner, especially for a typical home owner to do themself.

[jm2fly]

Nice Striper Duece! Is that picture recent?

[ACFIXR]

Square duct has less resistance to airflow, is cheaper to make, and more economical to install.

[gevans]

Square is easier to custom fab in the shop.
Rectangular is low profile
The shape matches the air handlers
Both look more expensive than round

Round provides the least friction loss
You can fit more on the truck
It's generic, and you can buy it in bulk
It's fast
It is available to any hack without a shop and therefore sometimes has a bad name.

[Lash]

Square duct has less resistance to airflow, is cheaper to make, and more economical to install.

I strongly disagree with everything said here...lol.


IMO...
Spiral is by far easier to install than sqaure as well as having less resistance to airflow when using full radius elbows. It can also be installed at least 2x faster. And with the use of gasketed fittings, it will also seal tighter than most square duct. Our shop can whip out the spiral like you wouldn't believe. Square duct is used because of the endless possiblities of changing dimensions while maintaining a required area, especially with space limitations. Round is somewhat limited in that area.

[Octopus]

I strongly disagree with everything said here...lol.


IMO...
Spiral is by far easier to install than sqaure as well as having less resistance to airflow when using full radius elbows. It can also be installed at least 2x faster. And with the use of gasketed fittings, it will also seal tighter than most square duct. Our shop can whip out the spiral like you wouldn't believe. Square duct is used because of the endless possiblities of changing dimensions while maintaining a required area, especially with space limitations. Round is somewhat limited in that area.

You got that friggen right!

[zzonko]

I strongly disagree with everything said here...lol.


IMO...
Spiral is by far easier to install than sqaure as well as having less resistance to airflow when using full radius elbows. It can also be installed at least 2x faster. And with the use of gasketed fittings, it will also seal tighter than most square duct. Our shop can whip out the spiral like you wouldn't believe. Square duct is used because of the endless possiblities of changing dimensions while maintaining a required area, especially with space limitations. Round is somewhat limited in that area.

Our shop can do spiral faster than any cheeser shop:LOL:

Also take into account the aspect ratio which is ideally less than 3:1 or 24 x 8, w/h=A.R.

[ACFIXR]

I strongly disagree with everything said here...lol.


IMO...
Spiral is by far easier to install than sqaure as well as having less resistance to airflow when using full radius elbows. It can also be installed at least 2x faster. And with the use of gasketed fittings, it will also seal tighter than most square duct. Our shop can whip out the spiral like you wouldn't believe. Square duct is used because of the endless possiblities of changing dimensions while maintaining a required area, especially with space limitations. Round is somewhat limited in that area.

I agree with you on the spiral.........also have found that a round duct can waste more space than a square duct but that the square duct can carry a higher volume or the same air at a lower velocity within the same dimensions. For example a 14" diameter duct verses a 14" square duct.

:grin2:

[zzonko]

I agree with you on the spiral.........also have found that a round duct can waste more space than a square duct but that the square duct can carry a higher volume or the same air at a lower velocity within the same dimensions. For example a 14" diameter duct verses a 14" square duct.

:grin2:

14" round = 154 square inches


14" square= 196 square inches

(aspect ratio 1:1)

[fearlessfurnace]

14" round = 154 square inches


14" square= 196 square inches

(aspect ratio 1:1)

but if the metal for the 14" square was made into round
248 square inches

almost 18" pipe

14" hole----
thats why god made sawsalls!!!!!!!!

[ACFIXR]

thats why god made sawsalls!!!!!!!! :cool:

The use of sawzall's by some in our trade ought to be outlawed. The cutting of stud's in bearing walls has bumped many contractor's to the top of the idiot list.Hell back in the 80's & 90's the largest contractor in the SW used to use chainsaws! :eek2:

[fearlessfurnace]

chainsaw, chainsaw, chainsaw

YYYYEEEEESSSSSSSSSS!!!!!!!!!!!!!!