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We moved to a new place where the dryer connection is 3-prong instead of 4-prong. The dryer was originally 4-prong, so we bought a 3-prong cord and installed it. It works fine, except I am not entirely sure if I installed the ground wire correctly.

Originally, there was a green wire on the cord itself, and that was connected to the screw on the top of the first picture. This is, I assume, used to ground the case and prevent shocks when touching the exterior of the dryer.

Now with the 3-pronged plug, there is no ground wire on the cord. So where does the existing green wire in the case go? Do I leave it where it originally was like in the first picture or do I connect it to the central terminal like in the second picture?

enter image description here

enter image description here

There's no bonding strap running from the case to any terminal. I can't tell where the green wire is connected to.

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4 Answers 4

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DO NOT connect the ground wire to the grounded (neutral) conductor, as this could lead to current flowing through the body of the dryer (and potentially through you).

The installation guide for the dryer will have wiring instructions for both 3, and 4 wire configurations. Check the manufacturers documentation for proper wiring, but I would say the first image is likely correct.

enter image description here

Instructions from random Maytag Installation Instructions (PDF)

3 Wire Cord

3-Wire Instructions

4 Wire Cord

4-Wire Instructions

Update:

After doing some research, and looking at dryer wiring diagrams. It turns out that the green/yellow wire is not a ground wire, it is a neutral to case bonding wire. When this wire is not in use (in a 4-wire installation for example), it is simply connected to the neutral terminal and is unused.

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  • Well, in his second image he's connecting the ground-wire to the neutral-wire, not the body of the dryer to the neutral. So (unless there's a loose wire that would actually require the safety of the ground) that will likely just trip the GFCI when he tries to turn the dryer on.
    – BlueRaja - Danny Pflughoeft
    Aug 9, 2013 at 17:12
  • @BlueRaja-DannyPflughoeft Maybe. I'm assuming the green/yellow wire in the image is connected to some internal components of the dryer. So by connecting it to the grounded (neutral) conductor, you're providing an alternative path to ground through anybody that touches the dryer (or whatever internal parts are bonded to this green/yellow wire. This assumption may be wrong.
    – Tester101
    Aug 9, 2013 at 19:48
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    It turns out we were both wrong, and your update is correct - the green-yellow wire is not a grounding wire, it's actually connected to the neutral. This allows the dryer to be grounded even when you don't have a dedicated ground wire. This is, surprisingly, allowed by the NEC. (also, I now know that most dryer's don't have GFCI's, because dryer-GFCI's are insanely expensive)
    – BlueRaja - Danny Pflughoeft
    Sep 11, 2013 at 22:55
  • @BlueRaja-DannyPflughoeft That's what I said.
    – Tester101
    Sep 12, 2013 at 12:07
  • At the end up the update, the answer says "it is simply connected to the neutral terminal and is unused." I believe that it is used. Because the neutral is (hopefully) grounded, this effectively grounds the case of the dryer.
    – Pigrew
    Nov 11, 2014 at 19:26
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Dryers with three-prongs are grounded using the neutral wire, when hooked up correctly (see @Tester101's answer for info on how to do that).

Normally grounding a device via the neutral wire is not allowed. However, the NEC specifically makes an exception for ovens and dryers:

250.140 Frames of Ranges and Clothes Dryers.
[...]
Exception: For existing branch-circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, the frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be permitted to be connected to the grounded circuit conductor if all the fol- lowing conditions are met.

  1. The supply circuit is 120/240-volt, single-phase, 3-wire; or 208Y/120-volt derived from a 3-phase, 4-wire, wye- connected system.
  2. The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum.
  3. The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE service-entrance cable and the branch circuit originates at the service equipment.
  4. Grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment.

It's important to note that this means on many (all?) dryers, the green grounding-wire should not be connected to the grounding screw when using a 4-prong wire, only with a 3-prong wire! So, make sure to find and follow the directions for your dryer when installing a new cord!

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  • Your final paragraph does not seem to match the quoted NEC text, nor the instructions shown for the dryer above. You write to never attach the 4-prong green grounding wire to the grounding screw, but I read the info to say that when a true ground is available in a 4 wire supply cable, only it should be connected to the equipment ground screw and the green/yellow bonding wire moved to the neutral terminal to separate neutral from ground; otherwise for a 3 wire cable w/out true ground the green/yellow bonding wire is attached to the equipment ground terminal.
    – simpleuser
    Jun 23, 2019 at 21:29
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There is a single phase that is split into two legs that goes into your house, known as "split phase". Each leg is 120VAC with 180 degree (directly out of phase) phase shift from the other leg. Some dryers and cook tops require only 240VAC to operate. In such cases, the "neutral" wire acts the same as the earth GND in a single 120V leg, which means this wire does not carry current when the circuit is operating normally. That's why the neutral and earth GND can be connected for such 240V outlets in your home (120V outlets should have separate Neutral and GND wires).

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  • This advice is location-specific. In the USA, we have split phase, with 180 degrees between the lines. Other countries provide 2 (of three) phases with 120 between them. In this sort of area having 120 V supplies, there would be 208 V between the two phases.
    – Pigrew
    Nov 11, 2014 at 19:18
  • FYI in the old days no ground was required on 220. The reason was 120 volts that is 180 degrees out of phase = 0 volts. There was an implied ground between the two wires. Not sure when the code changed but today the ground is there for protection.
    – John Peters
    Dec 30, 2014 at 22:09
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The Service panel is bonded... Ground to Neutral bar...On 3 wire 220 volt circuits. The ground is bonded to the Neutral connection as shown in the 3 wire diagram on the dryer..This still gives a path to ground. If a short should happen back to the source. The source being the transformer feeding the service entrance.

In a 4 wire.. The ground from the supply cord is screwed to the grounding screw..This protects the dryer from becoming energized..

Be advised.. I have seen this screwed up on Coffee makers. The heating element goes out. And the coffee maker becomes energized. Yet does not trip the over current protection ie Breaker....

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