A 45-degree rectangular transition chokes the duct because only one side was sloped
If only one panel is sloped and the duct depth shrinks, the fitting becomes a restriction. Keep the internal area consistent or get an approved revised fitting detail.
Do not build an offset that clears the beam by choking the duct throat down smaller than intended.
Check
Measure the duct depth through the narrowest point of the fitting.
Compare the restricted area to the planned duct size.
Check whether both top and bottom planes track the offset cleanly.
Look for noise, high velocity, or pressure drop risk.
Confirm revised fitting geometry before fabrication or install.
Steps
Measure the duct depth through the narrowest point of the fitting.
Compare the restricted area to the planned duct size.
Check whether both top and bottom planes track the offset cleanly.
Look for noise, high velocity, or pressure drop risk.
Confirm revised fitting geometry before fabrication or install.
Say this to your foreman
The 45 offset at [location] clears the beam but pinches the duct depth through the fitting. I think we need a true parallel-plane offset or revised fitting. Do you want this remade before we continue?