My question is what problems, if any, would be experienced by creating a "drop loop/trap" (similar to a plumbing trap) in a supply duct.
The problem is routing the duct down about 8" under a I Beam and then back up 8" to the original height(just under the joists.)
(a unusual configuration where the I beam is parallel to the joists, not the usual perpindicular)
Would this create a problem and if so what would be the problem and how serious would it be?
Would it be any better to go up and over the I beam (if possible) and then back down under the joists.
Thanks very much....Chris
Sometimes there are no other options but to do what you're describing. There are no serious problems to worry about and no codes that would prevent you from doing it.
The only thing to expect is a reduction in the airflow in that duct. It doesn't matter if you go under or over but I would chose the path of least resistance.