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In my house there was a 3-prong outlet for the dryer and when I opened it I saw that there is 4 wires and the ground and neutral are on the same terminal. Can I change the outlet to a 4 prong? The hot wires and neutral are 10 gauge, but the ground is 12.

Is this OK for the dryer?

  • Probably the neutral is connected in the panel, but you might want to verify. If you don't want to remove the front of the panel to verify connection of the neutral, you could just verify 120 V between each hot and the neutral. Alternatively using the meter in resistance mode verify near zero ohms between neutral and gnd. But do not connect the meter in resistance mode to a hot . – Jim Stewart Aug 16 '18 at 15:46
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First, separate neutral and ground at the receptacle, that should never have been done. Paralleling neutral is not allowed.

Second, go back to the service panel and make sure the neutral is on the neutral bus... And the ground is on the ground bus. Inside a main panel ("service equipment" as NEC describes it in RME's post above) don't be surprised if they use the same bar for neutral and ground. That is wrong to do in a subpanel.

Now install the new receptacle in the normal way. Hats off to the last guy for fitting the right cable.

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The answer to your question is found in NEC Article 250.142 Frames of Ranges of Clothes Dryers. I have taken the time to scan that section from the NEC Handbook which is the NEC with further explanations and examples. enter image description here

enter image description here

As you can see it has quite a bit of detail and the NEC board usually does not address a single appliance circuit as much unless there is a lot of discussion and debate in the community. My advice is to take this knowledge, but use your best judgement.

Stay safe

  • To all: Read carefully. "Grounded conductor" and "grounded circuit conductor" actually mean neutral. "Grounding conductor" etc. means ground. – Harper Aug 16 '18 at 19:03
  • To RME: well done posting this. I never knew. – Harper Aug 16 '18 at 19:07
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As long as you have 3 x 10-gauge wires + ground, you should be OK to put in a 4 prong outlet. The 3 prong outlets were indeed designed to bootleg the ground to the neutral, which was a bad idea. As one website noted

So, why did the NEC make the decision to switch from 3-prong to 4-prong dryer outlets in new homes? Although the old 3-prong outlets were effective at providing power to dryers, they had one major flaw: the ground and neutral wires were grouped together, creating the potential for shock. 3-prong dryer cords contain two ‘hot’ wires along with a third wire that contained both the ground and neutral wire. If a current happened to make its way onto the ground wire, it could travel up to the dryer.

The more recent 4-prong dryer cords feature two hot wires, a neutral wire and a ground wire. This eliminates the possibility for a ground current traveling to the machine, as it features a separate return path for unused power.

The ground wire is always smaller than the hot/neutral because it's not meant to carry a load like the other wires do.

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    Perfect explanation. But should also note that when you change the outlet you also have to remove the ground<->neutral bonding in the dryer. – manassehkatz Aug 16 '18 at 15:00
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    The manual for that dryer will have detailed instructions with a diagram showing how the connection block is to be configured for a 4-wire plug. – Jim Stewart Aug 16 '18 at 15:31
  • Thanks for the responses. I installed the dryer cord like the dryer diagram and the dryer was not working properly so I had an exchange and when sears came to install the new dryer they connected the neutral of the cord and the ground of the cord on the middle joint of the dryer. and they told me I did it wrong on the previous dryer. Is this correct? – Manuel Aug 31 '18 at 17:41
  • I checked the main panel and neutrals and grounds are on the same bus – Manuel Aug 31 '18 at 17:41
  • @Manuel Might want to ask that as a different question – Machavity Aug 31 '18 at 17:42

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