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Patrick Presti
2 Prong to 3 Prong

Hey Guys,

Got a question for you. My recent 1953 cape has many 2 prong outlets. I am looking to switch them over to 3 prong outlets. I checked the metal boxes and they are grounded. When I switched over to a 3 prong outlet, I added a ground wire from the outlet to the back of the box. I flipped on the breaker and the outlet shorted out.

I then decided to remove the ground I added and the breaker/outlet works fine. I even checked the outlet and the 3rd prong is grounded.

Any thoughts would be greatly appreciated.

Thanks,

Pat

HoustonRemodeler
Re: 2 Prong to 3 Prong

Pat,
Since the outlet is grounded to itself, it gets grounded when you screw the outlet to the metal box. No need for the extra ground wire. This is the typical wiring for commercial work with the ground in the metal of the box / wire.

Patrick Presti
Re: 2 Prong to 3 Prong

Thanks for the info. So it is fine the way it is now?

Thanks,

Pat

HoustonRemodeler
Re: 2 Prong to 3 Prong

Yes,
Unless Maurice says differently

Re: 2 Prong to 3 Prong

Pat, if you conected a wire from the box to the green screw on the new 3 prong receptacle and it tripped a breaker you may have what we call a "bootleg ground".

That is when someone with an ungrounded two wire system connects a green jumper wire from what they think is the neutral wire to the box. Then extends the two wire circuit with romex having a ground.

Electrically it now appears that the house has a three wire grounded circuit.

I suspect this is what happened in your case. The "hot" was tied to a metal box and energized it. This is very dangerous especially in a wet location. Say you plug in a toaster in a kitchen and touch it and the sink. You would get a very serious shock.

There are ways to do what you want to do but, finding and removing that "bootleg ground is the first step. Then, there are two options:

1) The best method: Run a green or bare wire (#12) to a good ground, such as a properly grounded panel or cold water pipe, to the circuit you would like to convert to three wire and use conventional 14-2 w/g or 12-2 w/g romex, from there.

2) Install a GFCI receptacle at the first ungrounded box coming from the power panel and attach one of the labels that came with the GFCI that says "ungrounded receptacle" to the cover. Also, attach one to every downstream receptacle cover.

You can now change out the two prong plugs to a three prong plugs dowstream and they will have a much higher level of safety. But, computers etc. will not be fully protected against static and lightning damage, as they should be.

JLMCDANIEL
Re: 2 Prong to 3 Prong

There should be no difference in connecting the ground wire to the box and the connection made ny the mounting screws to the box. If it cased the breaker to trip, you either shorted something out or connected to the wron screw.

Jack

Fencepost
Re: 2 Prong to 3 Prong

Check out this video that discusses bootleg grounds:

https://www.youtube.com/watch?v=iLk-6pvSlWg

Re: 2 Prong to 3 Prong
Fencepost wrote:

Check out this video that discusses bootleg grounds:

https://www.youtube.com/watch?v=iLk-6pvSlWg

Fencepost, good demonstration but saying the bootleg jumper from neutral to ground is OK, but may not be legal everywhere is wrong, dangerous and mis-leading.

Also, the beeper probe is useful for safety reasons but should be used very carefully for trouble-shooting reasons.
Having said that, I never leave home without one.

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