Duct/trunk routing - 45deg angles?

[CaLevi]

One of the 2 main trunks in our basement wastes a lot of headroom space. I wanted to know if there are any issues with running 45deg angles in main trunk lines.
The stairs are built in the middle of the house, so they routed the trunk line way out to clear the stairs to make a straight path, and I'm wondering if I can re-do it so that it runs straight with a 45deg leg in it that would run parallel to the stair well.

It would look like this :
____/-------- ; as best as keyboard characters can 'draw'.

[second opinion]

One of the 2 main trunks in our basement wastes a lot of headroom space. I wanted to know if there are any issues with running 45deg angles in main trunk lines.
The stairs are built in the middle of the house, so they routed the trunk line way out to clear the stairs to make a straight path, and I'm wondering if I can re-do it so that it runs straight with a 45deg leg in it that would run parallel to the stair well.

It would look like this :
____/-------- ; as best as keyboard characters can 'draw'.

It really should not matter as long as the dimensions remain the same. It will ad a friction loss but without seeing a layout of what you have it would be hard to be precise. Could you post a picture?

[heaterman]

As long as the fittings are constructed properly with radiused throats, the losses will be minimal.

[CaLevi]

Here is a picture :
http://hvac-talk.com/vbb/picture.php?albumid=2622&pictureid=15312

the green arrow is how I wanted to re-route the square ducting.

[second opinion]

Should not be a problem, as stated make sure your duct fittings are made with radius not squared

[dijit]

Also, make sure there are not two angle pieces too close together. There should be a fairly long straight section between the two turns.

[CaLevi]

The main trunks are square ducts, with the branches to the vents being round ducts. I'm not clear on 'radiused throats'/'duct fittings are made with radius not squared'. Can I not make these bends using square transition/angle pieces (assuming they exist)? or is the argument that I need to throw out the square existing and replace the main trunk with round ducts? I was hoping to re-use the square ducting and simply re-route it.

[heaterman]

No, the main rectangular trunk lines are fine. The 45* angles you propose should be radiused (rounded) both the outside curve as well as the inside curve (throat) to facilitate better air flow and less turbulance.