pulling wire thru steel conduit

[mistral9999]

Is it possible/code to pull three #10 and three #8 wires thru a 3/4" steel conduit?

Thanks, Matt

[RBM]

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

[Nexus7]

If you have no turns, you could probably get 6 #10 through, but I don't think it'll do you much good.

[Speedy Jim]

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. (250-95 table)

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.

Jim

[Nexus7]

Electrically looks OK, but how's he going to get all that around the bends?

[Bob]

[Calvin Henry-Cotnam]

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 area.

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 conduit's fill.

I have a "conduit calculator" available for free at

that comes with cross-section data for a number of different types of wire.

[RicodJour]

Good link. Thanks!

R