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I have a 3 prong 240v outlet for a dryer that reads 240v across both legs and 120 across the ground. When I turn the dryer on and have the multi meter to the ground and a hot leg it shows 120 but if I switch it to the b leg and ground it shows 40 then climbs up slowly to 120. The ground is new and goes to a new ground rod outside as well. I verified it isn't the dryer by plugging it into a different 240v outlet and it works fine.

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    Are you sure that it is ground and not neutral? Dryers usually require neutral and in olden times use only two hots and a neutral, but no ground. If it is using neutral, the plug/receptacle should have three slots. if using ground the plug/receptacle should have two slots and a round/D shape hole/prong.
    – crip659
    Commented Apr 19, 2023 at 22:44
  • If you are in the USA/Canada, that's not ground - it's a NEMA 10-30 outlet with no ground wire that has been banned for more than a quarter-century. Replace it and the cord to your dryer with the 4-prong flavor, NEMA 14-30, properly wired, which will take some work if you just connected the NEMA 10-30 Neutral to an outside grounding rod...
    – Ecnerwal
    Commented Apr 19, 2023 at 22:54

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Wow, so many things wrong with this setup.

The crux is that you are confused about the role of the 3rd pin on a 3-prong dryer. The third pin is NOT ground. It is neutral. You don't have a ground on a 3-prong dryer connection, and that's even more dangerous than it sounds!

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So right off the bat, the 3-prong socket was outlawed in 1996. You must use the modern, grounded NEMA 14-30. The dryer plug can easily be changed to 14-30 and the dryer's manual (search online) shows the procedure for doing that.

It has never been legal to connect that socket using "/2+ground" cable. The only cable that was ever legal for this socket was "/3 no ground" or "SEU", though /3+ground is legal of course except the socket isn't.

If you don't have neutral here, you cannot use an American electric dryer.

I'm not sure why you didn't run neutral, but if you were under the impression that 3rd pin was ground, that would explain it.

American electric dryers need 120V for everything except the heating element. Most likely that's because gas dryers use all the same components (except for the heating element obviously) and those are 120V. It can't work without neutral.

Now I suppose you could "hack the dryer" to use an autotransformer to supply its internal 120V loads. That's how manufacturers sell American dryers in the Philippines, where they don't have neutral at all. At that point you could use /2+ground cable feeding a NEMA 6-30 outlet (hot-hot-ground). Ground the dryer chassis and carefully isolate your created neutral from ground or chassis.

You cannot create ground with a ground rod alone.

You also need a ground wire back to the main panel.

That's because the ground is made of dirt, and dirt is a poor conductor - that's why we bother to mine copper instead of just wrapping dirt in THHN insulation and calling it good. The ground needs to be able to flow enough current to trip the breaker in the case of a short - and dirt just can't do that. The ground rod is there to protect equipment from static electricity and lightning, and to help somewhat with voltage gradients across the land.

If a ground wire back to the supplying panel is simply impossible, things can be done with GFCI to remove some of the danger.

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  • My apologies, my knowledge of wiring is very basic and still learning as I go. I had a electrician come out and he came to the conclusion that the ground was bad so he drove a 12 ft ground rod in the ground and wired that to the top pin so I thought that was how it was supposed to be done. Currently all the plug has is the 2 hot wires and then the ground wire. There is a bare wire in the receptacle not hooked up, but I'm not sure if it is a neutral or a ground
    – Brian
    Commented Apr 20, 2023 at 11:51
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    Don't let that electrician do any more work on your house.
    – KMJ
    Commented Apr 20, 2023 at 16:06
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    @Brian your "electrician" is dead wrong and is not an electrician at all. To be an electrician you need a license from the state that requires 5 years of apprentice work and passing an exam typically. Also installing a 3-prong dryer outlet has been illegal for almost 30 years. We'd have to see a picture of the bare wire to see whether it gives you any options. Or alternately, the writing on the outside of the cable, or its color - is it orange or yellow? Commented Apr 20, 2023 at 19:29

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