3 prong 30 AMP to 4 prong for dryer

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Old 04-24-19, 09:54 AM
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3 prong 30 AMP to 4 prong for dryer

Need some advice on this. I got a new dryer and it is 4 prong. I believe that going from 3-wire 30 amp to 4-wire means the addition of a ground connection. I believe that bundle of wiring screwed to the box is the ground I will need to connect to. But it looks like its aluminum, which I learned in a house built in the 60's was common, not sure about the rest of the wiring. The 4 prong outlet I will likely use is the Leviton 278-S00 which is AL/CU. I guess I just need to know the best way to connect the ground, should I stick with aluminum and pigtail to that ground lug? The only aluminum wire I see at the hardware stores is for electric fences... not sure if that will work and what gauge I need. Thanks!

 
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Old 04-24-19, 10:44 AM
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Hi, scrap this post, I didn’t realize you had a 4 conductor feed
Geo
 

Last edited by Geochurchi; 04-24-19 at 01:41 PM.
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Old 04-24-19, 12:15 PM
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Since you do have a 4 wire feeder I would switch to a 4 prong outlet. You can go to an electrical supply and get a short single piece of #8 Al XHHW and extend the ground from that ground lug in the box to the ground of the outlet.
 
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Old 04-24-19, 12:15 PM
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In a house of that age, you're lucky to have 4 conductors in the wall, although them being aluminum is not ideal. Since you have 4 conductors, it makes sense to upgrade your receptacle to a 4 prong NEMA 14-30R (like the Leviton product you mentioned).

It's a good idea to change our your high voltage receptacles after a few decades anyway.

The problem with aluminum wiring is twofold. Firstly bare aluminum develops an insulating skin/coating of aluminum oxide when exposed to the air. Secondly, aluminum can heat up and loosen up from the lugs due to thermal expansion. After years and years of use, if the connections aren't tight, there could be some arcing that occurs inside the electric box. The arcing could produce carbon buildup, which makes the connections even worse.

When you are ready to make the connection to the new receptacle, first scrape the aluminum conductors with a stiff wire brush to remove the layer of aluminum oxide. Then clamp them tight and apply an anti-oxidant paste.

After a few days of use, I would turn off the breaker, do a safety check to ensure power is off, and then re-tighten the lugs again.

To answer your main question, how to connect the ground wire:

In your case, since the available aluminum ground wire is pretty short, it may actually be difficult to pigtail it. I would personally try to replace that lug with a two conductor lug. The 2nd wire could be a piece of copper (I think #10 AWG solid copper or stranded equivalent).

https://www.homedepot.com/p/1-0-to-1...B2-5/100172941

 
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Old 04-24-19, 12:20 PM
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Do not put copper wire and aluminum wire touching together, use a two hole lug as show to keep the copper and aluminum separated.
 
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Old 04-24-19, 02:24 PM
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Yeah I was pretty stoked to see a ground wire in that receptacle. But yes not as stoked to see it was aluminum. Good call on the double lug, that seems like the way to go. I had considered swapping for a 3 prong cord, but I figured since I have the ground in the box that the safest and best long term solution would be to go 4 prong outlet. We just bought the house and the inspector said we had a mix of copper and aluminum at the panel, so I am not sure what that looks like outlet wise for the rest of the house, so that is the next step. Hoping the rest is mostly copper or I guess I will be looking at getting some AlumiConn connectors...

Thanks y'all. I will update with any questions.
 
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Old 04-24-19, 02:56 PM
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FYI aluminum is perfectly safe on ranges, dryers and panel feeders as the receptacles and lugs for these devices are rated for use with aluminum and there are no field splices. It is a good idea to use an anti corrosion compound like Noalox when terminating aluminum wire in lugs, but it is not strictly required per code.

Aluminum wiring is really only a hazard when used in residential branch and lighting circuits. While you're checking out the panel, verify if the home inspector was referring only to the large appliance circuits or if there are also aluminum branch circuits in your house.

Instead of the double lug, it would also be acceptable to tap a 10-32 ground screw into the back of the metal junction box, and from that run a short piece of #10 copper to the receptacle. Ground conductors do not need to be directly spliced as long as they are bonded to a metal box.
 
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Old 04-24-19, 04:37 PM
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Like just tapping this into the box... https://www.homedepot.com/p/Ideal-12...392S/202894314
 
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Old 04-25-19, 06:18 AM
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Yes like that, but with #10 copper instead of #12.
 
 

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