shorton2
Mechanical
- Nov 3, 2008
- 43
I am working on an optimized residential duct design usign Manual D equivilant friction method.
All ducts are located in the same space that is being conditioned (basement). I will have some rigid, and some flex ducts.
I would like to keep the friction losses down as much as possible for both sound and to allow a variable speed blower to work as little as possible (lower rpm).
I can of course make the ducts very large, but I do not know the practical limits on the air velocity. I have been advised by some expereinced HVAC people that about 400 fpm is good for residentail design.
I do have one room that is sensitive to duct noise (home theater type room) so I wan tto minimize sound there. But, I don't want the air moving so slow that it casues other issues.
I do understand the main issue may be the velocity at the register and how that affects the register's throw. I can reduce the duct diameter just before the register for this purpose and add the associated P drop.
If the ducts were in unconditioned space, I can see the need to keep the air moving quickly so it does not heat/cool off before it gets to it's target. But since these ducts are colocated, that appears to be either no, or at least less of an issue.
Can anyone offer any advise or reasoning for the minimum velocity in such ducts? Particularly the final supply lines/branches.
All ducts are located in the same space that is being conditioned (basement). I will have some rigid, and some flex ducts.
I would like to keep the friction losses down as much as possible for both sound and to allow a variable speed blower to work as little as possible (lower rpm).
I can of course make the ducts very large, but I do not know the practical limits on the air velocity. I have been advised by some expereinced HVAC people that about 400 fpm is good for residentail design.
I do have one room that is sensitive to duct noise (home theater type room) so I wan tto minimize sound there. But, I don't want the air moving so slow that it casues other issues.
I do understand the main issue may be the velocity at the register and how that affects the register's throw. I can reduce the duct diameter just before the register for this purpose and add the associated P drop.
If the ducts were in unconditioned space, I can see the need to keep the air moving quickly so it does not heat/cool off before it gets to it's target. But since these ducts are colocated, that appears to be either no, or at least less of an issue.
Can anyone offer any advise or reasoning for the minimum velocity in such ducts? Particularly the final supply lines/branches.
