How to Ground a Two-Prong Electrical Outlet | Ask This Old House

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Ask This Old House master electrician Heath Eastman explains the purpose of a ground wire and then grounds an outlet for a homeowner.

Any work that involves working on the electrical panel can be dangerous and should only be done by a licensed professional.

In this scenario, Heath found that none of the surrounding receptacles or their wiring were to code, so he removed and replaced them with a 12-2 NM cable and a single GFCI outlet. These materials can be found at any home center or electrical supply store.

Time: 3-4 hours
Cost: $400
Skill Level: Professional Only

Tools:

Shopping List:

Steps for Replacing Two-Prong Electrical Outlets:
1. Heath starts by explaining the purpose of a ground wire:
a. To complete an electric circuit, power must be sent from the panel, through the hot wire, and back through the neutral wire. Under normal operating circumstances, the electric devices in a home should work without issue.
b. If a device faults, meaning that the current in the circuit strays from the path for a variety of circumstances (water near exposed wires, two wires touching, etc.), that current will go wherever is easiest, which can create a shock hazard.
c. A ground wire is a bare piece of copper that goes into the jacket of wiring with the hot and neutral wires. Due to its extreme conductivity, excess current from a fault will naturally travel on the bare copper and cause the breaker to trip.
d. While the lack of a ground wire won’t prevent an electrical device from working properly, the ground wire is an important safety device that is now part of the electrical code.
2. In most cases, grounding a receptacle means running new wiring with a ground wire in it. Start by cutting power to the main electrical panel.
3. Run the NM cable from the panel to the location of the outlet. This process could result in a wide variety of obstacles, including getting the cable through floors and behind walls, or in this case, running the cable across basement joists and stapling them in place with electrical staples and a hammer. The ease of running the wire will determine the overall cost of the job.
4. Next, wire the receptacle. If an old two-prong receptacle is still in use, that will need to be replaced with either a three-prong receptacle (in living spaces) or a ground fault circuit interrupting receptacle (in bathrooms, kitchens and basements), depending on its location. Wiring will usually require a pair of pliers and a screw driver to secure the wires to the receptacle.
5. Back at the panel, wire the new wiring to a circuit breaker. In this case, Heath used an arc fault breaker and added it to the panel. The hot and neutral wire to the breaker, the neutral pigtails to the neutral bar, and the ground wire ties into the grounding bar. These wires can be secured with a screwdriver.
6. Turn the power back on.

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How to Ground a Two-Prong Electrical Outlet | Ask This Old House
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I’ve heard elsewhere that you’re not supposed to run Romex through conduit; just run the THHN wires instead. Never heard a good explanation of why, though.

bobperlman
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I purchased an older house (1959) with two conductor wiring throughout. Lived in it for a few years but when I installed an outdoor pool requiring additional grounding, I installed a grounding "pad" for the pool. Since I was at it, I did the same thing for the house. I dropped 5 8 ft. copper dowels around the house and took separate ground wire to each of the receptacles. Every receptacle had it's own discrete ground after each receptacle was replaced. I used the existing wiring in the house because too many walls would have to have been torn up. I was now up to code and safe. Then again, this was 30 years ago and I'm certain codes have been updated...but it worked and has worked for an additional 3 decades.

rollingthunder
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that little drill dust collector is nice

TheBeowulf
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This was the right repair done the right way. The cost in the description is low but it's probably an old video.

lloydmills
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BEWARE! Just because you turn off the main breaker does not mean that there "are no energized parts in the panel." The two mains coming in from the meter will still be hot, so you do still have to be careful while working with the cover off.

Thumbsdwn
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I love how Heath and the rest of the TOS crew can take what can sometimes be an overwhelming or confusing topic and simplify it down with practical and relatable demonstrations. If I'm not 100% sure about something, I always turn to TOS first. Would love to buy everyone at TOS a "cold one" for the knowledge and confidence I've acquired from them over the years!

davidhemphill
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Thanks for the simple and spot on explanation. The irony is that it is so simple and you can’t get anyone to state the obvious instead they make it confusing and complicated. Though I’m 63 years old I just completed an electricians course and obviously don’t consider myself an electrician. I know there will be plenty of learning to do and will proceed with caution but just this simple explanation makes a difference. Thanks again.

alfredretana
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This electrician is good. I like him. Fast, efficient, thorough.

BlackSwan
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I actually like the new guy Heath a lot. Clear, concise and seems to know what he's doing

moutrap
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How to Ground a Two-Prong Electrical Outlet: Re-wire the entire circuit.

TENTHIRTYONE
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If you were discouraged by this answer, another way to provide some safety is to add a GFCI outlet or breaker. Not as good as a real ground, but much better than giving up and leaving it as is. Yes, a GFCI will work without a grounding wire.

ryanjcampbell
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Good video, thanks. Note that the dryer is a gas dryer. A washer and a gas dryer can be on the same dedicated 120V 20A circuit. An electric dryer requires a dedicated 240V circuit, typically 30A using 10-gauge 4-wire cable (10-3 with ground), which for residential in the USA color-coded orange.

gregorymark
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That guy didnt know what a ground was and you're trusting him use the mulimeter to tell when the powers off?

Kentboy
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My 1961 on slab home in Thousand Oaks had two prong receptacles. Installed GFI's on two wire fine, in the electrical code

johnrobinson
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Just setup a socket with GFCI so I can get the dehumidifier running in a basement! Not skilled enough/have the equipment to change out the entire line, but I appreciate the video, and that they showed you how to. Might attempt it when I'm a bit more competent. Now on to 50 other things I've gotta do for this place! :D

Sawta
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Buying a house that's from 1944, but in pristine condition (fewer issues than the "new build" I bought in 2017), having to just replace outlets with GFCI. Luckily the major places like laundry, kitchen, and bathrooms were all converted by previous owner. But the rest are 2 prong...and I really don't want to explode my TV.

j.s.
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This should have been titled "if you have a two-pronged outlet replace it"

tenthdimension
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I've never seen the bag and drill before. I learned something new.

dialaprohq
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the title should be "how to install a new electrical outlet" he didn't ground a two-prong outlet, he installed a new one.

Hisham
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Good video. Simple, straight up explanation with correct options. I should show it to some of my customers. It is some of the comments I worry about. Proper grounding is one of the most important safety issues when it comes to electricity. Older and even newer homes have their own unique wiring methods. It could be handyman doing work in the past. When the grounding wire was added to the cables many electricians did not know what to do with it. Keep in mind that if there is no proper grounding conductor present, your surge protectors might not work.

keithb