Duct Hanger Load and Count
The weight each duct hanger carries at a chosen spacing and the count a run needs: load = per-foot weight x spacing; count = ceil(run / spacing) + 1. A duct at 5.5 lb/ft on 8 ft centers puts 44 lb on each hanger, and a 40 ft run takes 6 hangers; a heavier lined duct at 9 lb/ft on 10 ft centers is 90 lb/hanger over 5 hangers - wider spacing means fewer hangers but more load on each. SMACNA sets the max spacing (~8-10 ft rectangular); large duct goes on a trapeze.
Formula and source
load_per_hanger_lb = duct_lb_per_ft x spacing_ft; count = ceil(run_ft / spacing_ft) + 1; utilization = load_per_hanger_lb / hanger_swl_lb.
Duct-hanger load / count identity by name (tributary weight per hanger; count from run and spacing); first-principles statics.
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