GFCI Open Ground and Water

[ozofprev]

Rick,

First, if you think you might be dumb as a pile of rocks, then you're not.

It sounds like you have a handy dandy, but not a super handy dandy. A good analyzer will indicate bootleg grounds. If you are using one of those little traffic light testers, they don't always tell the truth.

Originally posted by zeb

I may be dumb as a pile of rocks,,but if on a 2 wire system and a ground fault outlet and I stick my handy dandy tester in it and I see the center light come on (ungrounded??) I then press my super handy dandy tester button and nothing happens, then the outlet is not working proper for gfci??? My question is will a tester trip a GFCI on a 2 wire system. Jim I know that that this is small stuff for you along with many others,however I may have been sleeping during this part.

[Jim Katen]

Originally posted by zeb

I may be dumb as a pile of rocks.

Consider this: At an inspection yesterday, I spent 35 minutes explaining this very question to an electrical engineer/homebuyer. He was unable to grasp the concept until I drew a diagram. He wasn't as dumb as a pile of rocks.

but if on a 2 wire system and a ground fault outlet and I stick my handy dandy tester in it and I see the center light come on (ungrounded??) I then press my super handy dandy tester button and nothing happens, then the outlet is not working proper for gfci???

No. What's happening is that your tester is unable to create a ground fault at that receptacle. Your tester "tests" GFCIs by shunting some power to the ground pin. On a conventionally wired receptacle, this creates a ground fault and "tests" the GFCI. If there's no grounding wire connected to the grounding slot on the receptacle, the shunting will do nothing -- there'll be no ground fault. (Interestingly, it will energize all of the grounded portions of the receptacle. So if you push that button and let your knuckle touch the coverplate screw, it'll bite you - presuming you're grounded, of course.)

My question is will a tester trip a GFCI on a 2 wire system. . . .

The hand held testers won't trip a GFCI on a 2-wire system. The GFCI's integral test button will. It doesn't test the circuit by shunting to ground, instead it shunts a small amount of power around its sensing coil. If the coil's working, this causes the GFCI to trip. No ground is necessary.

- Jim Katen, Oregon

[ozofprev]

Hmmm, you da man Katen!

My thinking was that the handheld would trip the 2-wire through - in this case - the bootleg ground Zeb mentioned.

I'll have to draw a picture for myself wrt this.

[chicago]

Let me get this straight Jim.

I can play a practicle joke and make my own crazy joy buzzer with a three hole recepticle that lacks EGC run a wire from the recepicle box to my victim then press my test button on the handy dandy traffic light tester for a barrel of laughs?

[Jim Katen]

Originally posted by ozofprev

Hmmm, you da man Katen!

My thinking was that the handheld would trip the 2-wire through - in this case - the bootleg ground Zeb mentioned.

I'll have to draw a picture for myself wrt this.

Where did he mention a bootleg ground?

- Jim Katen, Oregon

[Jim Katen]

Originally posted by chicago

Let me get this straight Jim.

I can play a practicle joke and make my own crazy joy buzzer with a three hole recepticle that lacks EGC run a wire from the recepicle box to my victim then press my test button on the handy dandy traffic light tester for a barrel of laughs?

Yep, you're all set for next April 1st.

You can make a similar toy by wrapping a small piece of wire around the 3-light tester's ground pin and wrapping the rest of the wire around the body of the tester. Hand them out for free to realtors. They love a good practical joke.

- Jim Katen, Oregon

[ozofprev]

Jim,

He wrote that the center light came on, and he parenthetically stated that this surprised him. Sounds like a false ground to me.

With no bootleg, obviously no trip. But if the neutral conductor is connected to both the neutral and ground terminals at the GFCI, the handheld will trip the GFCI.

Originally posted by Jim Katen

Where did he mention a bootleg ground?

- Jim Katen, Oregon

[Jim Katen]

He wrote that the center light came on, and he parenthetically stated that this surprised him. Sounds like a false ground to me.

On my three-lighter tester, if the center light comes on, it means that the receptacle is ungrounded. (GB tester.)

With no bootleg, obviously no trip. But if the neutral conductor is connected to both the neutral and ground terminals at the GFCI, the handheld will trip the GFCI.

With the newer GFCIs, yes. With older ones, they may or they may not.

- Jim Katen, Oregon

[ozofprev]

Jeez, I haven't used my little tester in so long, I forgot what those lights mean. I just dug it out of the bag, and you're right of course.

I understand all of this now, except why the older GFCI's may or may not trip with a false ground.

I like my Ideal analyzer - three green is good! Reminds me of landing gear indicator lights. "Three green" is part of every landing checklist (well, not water landings).

[Jim Katen]

Originally posted by ozofprev

. . . I understand all of this now, except why the older GFCI's may or may not trip with a false ground. . .

That's an excellent question. The reason is . . .

. . .

. . .

. . .

I have no friggin' idea.

Years ago, I'd occasionally come across an old GFCI that wouldn't trip with my 3-light tester but it would test fine with it's on-board button. My tester was showing that the receptacle was properly wired. When I took the sucker apart, however, I found that it's ground was bootlegged.

From this I presume that bootleg grounds are invisible to the older GFCI circuits.

I don't know why, though. It's a good question for Earl Roberts.

- Jim Katen, Oregon