Is 1/2" PVC conduit sized properly for three #10 THHN wires ?

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  • Is this conduit schedule 40 or schedule 80? – ThreePhaseEel Sep 12 at 1:26

Yeah, that's legal.

If it's a particularly complex pull, larger pipe size can help. It can also help with the fact that you can easily put 4 circuits in a conduit (if it meets the fill rules).

Now, since you mentioned this is a dryer and you are running hot/neutral/ground... If it's a gas dryer you are on the right track.

If it's an electric dryer, we must deep-dive into the arcana of dangerous and obsolete dryer connections. Old 3-prong dryers used no ground, and worse, they attached the chassis of the dryer to neutral. This has the potential of being dangerous in several ways. As such they have been outlawed for 30 years. And even when they were legal, it was NEVER legal to use /2+gnd (black white bare) to connect them - though it was done shamefully often.

Since you are doing a new cable run, you MUST bring it up to current Code. This isn't far out of your way; you just need to use 4 wires in the conduit instead of 3. The 2 hot wires can be the same color - but neutral must be white, and ground must be green or bare.

I for one recommend using stranded wire, because it's a lot easier to pull.

By the way, if you use EMT metal conduit, the conduit is the ground - one less wire.

And yes, you will need to convert the dryer socket and cord to NEMA 14-30.

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  • Did you mean 4 conductors? There is no limit to the number of “circuits” except by wire fill volume. – Ed Beal Sep 11 at 20:02
  • @EdBeal Nope, 4 circuits max because OP is using #10 for a typically 22A load. If OP went to 5 circuits, the #10 wire would only be good to 20A, and could not support the load. – Harper - Reinstate Monica Sep 11 at 20:56
  • Can the neutral and ground be taped white and green? – JACK Sep 11 at 21:04
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    @JACK not at #10. At #6 and larger (smaller gauge numbers) (I believe that's the size it starts at) you can do that, but #8 and #10 you have to use the correct colored wire (white or gray for neutral, green or bare for ground) for them. – Ecnerwal Sep 11 at 22:05
  • I don't understand the down vote. – JACK Sep 12 at 0:00

You can pull up to 4 #10's in 1/2" conduit. If you give us some more info we might be able to help you further.

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  • Thanks... I'm eliminating the existing 30A aluminum wire to the dryer in the garage, about 8 feet from the panel. I picked up 1/2" pvc and a few sweeps, #10 THHN black, neutral and ground. The existing dryer cord is a 3 prong which Id like to keep or should i pull another hot and spend on a new cord and receptacle? Thanks for the wisdom – Peter F Sep 11 at 19:52
  • Table c.10 in annex c would be the code ref please pull both hot’s neutral and a ground to be code compliant. No more than 4 90 degree turns between pull points. – Ed Beal Sep 11 at 20:00
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    Those three prong plugs are considered dangerous, there's no ground. If your redoing the feed, run the four wires and install a NEMA 14-30 outlet and get a 4 prong plug and cord. – JACK Sep 11 at 20:03
  • Thanks and will do. – Peter F Sep 11 at 20:14
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    You will have to change the wiring inside your dryer for a 4-prong cord, but that's typically laid out on the back of the dryer itself - if not, look it up for your model of dryer. There will be a jumper that is connecting the case to neutral now, and it will (typically) move to a "storage" position when you make a 4 wire connection with a ground wire as well as the neutral wire. – Ecnerwal Sep 11 at 22:08

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