How do those 2 to 3 prong grounding adapters work?

Question

I recently moved to an older rental. Almost all of the outlets are two prong. So I purchased some 3 prong adapters and an outlet tester.

When I just stuck the adapter in, the tester showed the connection as ungrounded. As soon as I screwed the adapter to wall plate with the wall plate screw, the tester showed I had a "correct" (grounded) connection.

In lay terms, how does one little screw accomplish this task?

Is this grounded adapter as good as a regular 3 prong grounded connection?

Answer 1

it doesnt mean squat.
the box is not grounded 90% of the time in an old home if it only has 2 wires going to it. the tester showed open ground and the outlet was wired correct. the outlet has a metal bracket that holds it together, that bracket has contact with the netural side of the outlet. the netural side of wiring is in contact with the ground bar in the panel. (new Panel installs have changed) so the tester showed it was grounded (through the netural) if the outlet was wired in reverse (hot to netural side) the tester would have showed reversed connection and open ground. Sometimes i cheat and put a 3-prong outlet in there and connect a jumper wire from the netural side of the outlet to the ground screw on the outlet. Everyone will say different and how bad that is but its worked for 20yrs for me. its no different than using the adapter. they both give you the asumption that its "grounded"
Now if you have the outlet reversed wired and you try to do the jumper.. it'll spark and blow the breaker-so you need to know forsure which is the netural

Answer 2

You are correct, the screw must be attached to have the possibility to provide ground. Your tester confirms that perhaps the wire gong to the outlet box either has a ground and is wired to the box, or is a metal clad type wire. It can be as good as a 3-Prong if it has the ground wire. I don't believe the metal clad type carries quite the same guarantee. (The cladding isn't copper, and if it is old, it isn't aluminum either. So it is a lesser conductor. The joints/connections would be more subject to corrosion than with copper wire, etc.... Still better than K&T or plain old two-conductor.)

Adapters are a pain. You might be better off shutting off the breaker and opening the box. If the box has a ground wire, install a proper 3-prong outlet in. Home Depot and other hardware stores have wiring guides for the layman at $10 to $15.

Otherwise consult an electrician. You can stage this work. Start by having them do the kitchen and bath so they can put in the ground fault safety outlets where they need to be as well. Then as your budget permits, the living room and so on.

Answer 3

Grounding Adapter

Answer 4

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RE:
How do those 2 to 3 prong grounding adapters work?
I recently moved to an older rental. Almost all of the outlets are two prong. So I purchased some 3 prong adapters and an outlet tester.

When I just stuck the adapter in, the tester showed the connection as ungrounded. As soon as I screwed the adapter to wall plate with the wall plate screw,...

Answer 5

The assumption is that the receptacle box is grounded, when the receptacle is connected to the box the metallic part of the receptacle is connected to ground, so when you connect that little green wire on the adapter using the receptacle cover plate screw it should be grounded. This is only true if the home is wired using a two conductor metal clad cable or M.C. if the wiring system is knob&tube the box is not grounded. If this is the case consult with an electrician.

Answer 6

You didn't mention the appliance you'll bring here. Though you have the 220V/50Hz, I hope it isn't a problem with our 60Hz cycle that may affect your appliance. The 125V adapter without grounding is not a problem here as long as your appliance is not having high amperage e.g. aircons, etc. Grounding is use for safety purposes to redirect the stray current into the earthground and prevent someone to be electricuted. Btw, new electrical installations have provisions for grounding under the Philippine Electrical Code.

Answer 7

the green wire actually uses the nutral wire as the ground. they work the same way as if it were grounded.