Surefire test for a working ground in/of 3-prong outlets?

I was reading that not all 3-prong outlets have a working ground - nothing sinister, just previous owner home repair that didn't bother to insure grounding integrity. This house was built in 1940 so I'd like a way to test all the outlets.
Thanks, mikey
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mikey wrote:

Hi, Little plug in tester from RS? Tony
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mikey wrote:

Surefire way - make sure the power is off to the outlet in question, remove the wall plate, and then remove the outlet and inspect the wiring.
I've got a 1949 house that used two conductor, rubber coated romex like stuff, so most of the outlets are still two prong. The grounded three prong outlets in the house are grounded by 1) new romex with a true ground wire inside, 2) flexible conduit (bx?) where they had a 220V outlet put in for a big A/C in the living room, then converted back to a 110V outlet, and 3) two prong outlets converted to three prong when an electrician ran a dedicated ground wire to the outlets.
Perhaps an electrician can offer a better suggestion?
Bob
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You're going to have to visually inspect. A plug-in tester reading a positive result is only confirming it's ability to pass current from the line to the ground pin. A tester like that can be "tricked" if there's a connection between the ground pin and the neutral, and I've seen it done on an outdoor outlet for a small pond pump.
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A light bulb, in a socket that is wired between hot and ground.
Make sure the bulb lights to full bright. Using a 60-100 watt bulb will check that the ground connection is good enough to flow some real current.
The little handy testers only use a neon lamp, which doesn't draw enough current to test the ground wire, making it a quick and dirty test.
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Wow guys, What a great group. Thank you so much. And what a great starting point.
One question to John if I may: What exactly does visually inspect entail? I replaced a light switch in this new home and noticed that the copper grounding wire was attached as it should be, but with closer inspection, the other end of the wire was attached to nothing. mikey
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040716 0218 - mikey posted:

Now that's a bummer. It would be in your best interest now to examine all of the outlets and see just how the grounding was installed. If the ground wires in receptacle outlets are just touching the box as you had noted in the switch, this would make the box hot if there was a short in an appliance plugged into it if the box was not properly grounded. The circuit interrupter would not open the circuit, a very dangerous condition. Of course, the lightbulb tester recommended would detect this condition.
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Hi again, Just on the chance that someone gets this far in this thread, I want them to know that I don't trust my knowledge and skills enough to continue on my own.
I contacted an electrician that a neighbor of mine knows is good. I think I'll sleep better at night knowing that what's needed was done right.
Thanks again for your help, mikey
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John Hines ( snipped-for-privacy@newsguy.com) said...

This test is ideal for checking the itegrity of the connection to the ground pin (a flakey connection can show as good on a handy tester but will not make a 60-100 watt bulb glow to steady full brightness).
HOWEVER, a visual inspection should also be done to ensure the ground pin is not simply wired directly to the neutral at the outlet or somewhere other than the service panel. If this was done, the above test will show a good ground when in fact it is not.
--
Calvin Henry-Cotnam
"Never ascribe to malice what can equally be explained by incompetence."
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