There are some technical requirements
conductor < 20% of gutter area
must derate in nonmetallic gutters
Cu busbar i density <1000A/sq in
sounds temperature related?
perhaps they looked at temp rise and determined a max fill
gutter area will always be 5 times conductor area
some relationship of gutter area, conductor area and current to limit temp rise?
#12 20 A x 30 = 600 A ( or 25 A per ckt?)
Cu Area = 0.154 sq in
gutter area = 0.77 sq in
P loss = 612 W/LF
Gutter vol per LF - cond area = 7.39 cu in
Gutter surface area per LF = 42.1 sq in (assuming sq gutter)
W/cu in = 82.8
W/sq in = 14.5
#3 100 A x 30 = 3000 A
Cu Area = 1.239 sq in
gutter area = 6.195 sq in
P loss per = 2160 W/LF
Gutter vol per LF - cond area = 59.47 cu in / LF
Gutter surface area per LF = 119.5 sq in
W/cu in = 36.3
W/sq in = 18
if a relationship exists I can't see it
someone needs to do it for a dozen cond sizes on excel and plot
maybe calc temp rise of the volume?
