It's probably not physically possible and definitely a code violation. You
also have to consider that when you pull multiple conductors through a
conduit, you must derate the capacity of the conductors as well
Looks good to me.
40% fill for 3/4" pipe is 0.2100 sq in.
3 #10 THHN = 0.0552 sq in.
3 #8 THHN = 0.1119 sq in.
Throw in a bare
#10 equip ground = 0.008 sq in.
TOTAL = 0.1751 sq in. (less than allowable fill)
Apply the de-rating factor from Note 8:
#10 THHN 40 Amp X 80% = 32 Amps, so 30 Amp protection is suitable.
#8 THHN 55 Amp X 80% = 44 Amps, so 40 Amp protection is suitable.
It depends on what the insulation is! It is the cross sectional area
that matters, as you are not supposed to exceed 40% of the conduit's
If all these wires have T90 Nylon insulation, then their cross section
area is only 31.8% of the conduit's. If they are TW75, then they are 39.6%,
so they would also fit. If they are RWU75 EP, then they are 63.8% of the
I have a "conduit calculator" available for free at http://daxack.ca that
comes with cross-section data for a number of different types of wire.
"Never ascribe to malice what can equally be explained by incompetence."
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