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So you've decided to add some new electrical wiring around the house and you've decided to use conduit. The pressing question comes up and you're not sure what the answer is. Just how many wires are allowable in conduit anyway? Can I just stuff the conduit full by pulling until my face turns blue? Maybe I should hook the end of the fish tape to my pickup to force them in? You know the old saying...If it doesn't fit, force it!

Well as much as I'd like to have the videos of these feeble attempts, that is certainly not the proper method for pulling wire in conduit and it certainly is not allowable by the National Electrical Code. This article gives some very good examples of different conduit types and some common sized conduits used in home wiring. The table provided details common electrical wire fill for different sized conduit. Do you know how many wires are allowed?

Comments

September 17, 2010 at 5:45 pm
(1) Mat Loory says:

Its interesting that such question doesn’t get a simple answer. Most do it your self projects involve going to the hardware store and buying parts. I had to run three 12 guage 3 wire unsheathed cable into my backyard. I ended up using a 1″ PVC conduit, it had two bends in the run at 1″ and 15 ft. I used a bottle of lube mostly by lubing up the opening and dragging the wire thru it. I peeled back the wire 5 inches and attached only the center wire to the fish tape. I clipped off the others to make the end connection pointed. I placed all three wires together and taped in a stack arrangement. I stretched the wire out on the ground and bound bunch of wire together every 4 feet together. I hand fed the wire into the opening at the end which was most convient to pull from. It was a tug but it came thru with minimal resistance. I added two additional turns at the end of the PVC after pulling the wire thru.

So how many cables go thru a 1″ conduit? Three 12-3 cables. And yes, one person can pull cable.

November 17, 2010 at 4:24 am
(2) Isaiah Fairhurst says:

According to the NEC 2008, annex C, the number of conductors allowed in a piece of conduit are calculated depending on wire size and type and conduit size and type. As an example, for outdoor conduit runs, your conduit should be either Schedule 80 PVC or rigid metallic conduit. You also can only fill the conduits 40% full as this helps to allow heat disippation caused by current running through the wires.

These fills don’t take into account the insulation if you’re using a cable of 12-3 or 12-2, etc…

1″ EMT – 26 12AWG THHN conductors
1″ ENT – 23 12AWG THHN conductors
1″ FMC – 24 12AWG THHN conductors
1″ IMC – 29 12AWG THHN conductors
1″ LFNC-A & LFNC-B – 25 12AWG THHN conductors
1″ LFMC – 26 12AWG THHN conductors
1″ RMC – 26 12AWG THHN conductors
1″ Schedule 80 – 20 12AWG THHN conductors
1″ Schedule 40 – 25 12AWG THHN conductors

I make no assumptions and assume no liability as to the validity and accuracy of this information.

October 6, 2012 at 2:35 am
(3) Steve B says:

It’s not until one day you cut open a conduit stuffed with wires and find some, melted together, do you ask why, and realize there was a heat build up, and that’s why you are not allowed to over-fill a conduit.

May 12, 2013 at 9:06 am
(4) Mr.G says:

Can I run a #6/3 in a 3/4″ pvc for 8 ft run or do I need 1″ pvc for more space inside for hot tub usinf 38-43 amperes.

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