electrical puzzler

 

Today I replaced a 3 pronged outlet because a plug would not stay inserted. When I looked closely, the bottom cracked.

Upon removal, it only had 2 wires. It said 9-91 and cost $0.59 from True Value. Those were the days, the new one was $2.18!

Funny thing is before, a power strip showed it was grounded, as did a tester. After, the same. Could it be the actual electrical box is grounded? maybe they did it in 1991? The house is 1952....

Probably armored or BX cable

Metal boxes attached to armored, or BX, cable—a type of wiring commonly found in old houses—generally are grounded; the cable's flexible metal jacket serves the same purpose as a dedicated ground wire.

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John from PA

box ground

the earth wire is screwed to a screw in the back of the box, there is supposed to be a pigtail from that screw to the earth on the receptacle, but way too many broke over years,
It functions, but a valuable safety feature disappears when removing or replacing the device
without the pictail
when the device is pulled out of the box it is no longer grounded, if there is a wiring fault upstream and pulling the breaker did not disconnect, you're a crispy critter

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If only ..

would

it mean current needs to return through the tiny screw from the AC receptacle, to the metal box? Can that screw handle it? Isn't it still less than ideal? and good point the newer boxes seem to be PVC or whatever the material is...

As mentioned I don't know what I'm accomplishing if anything, but when I installed SharkBites, I put ground clamps on both sides of it, then a 8 gauge wire. I figured the SharkBite has o-rings inside so not really sure if electricity passes through it. I do have a rod driven in the ground to the panel, and then a ground clamp from the circuit panel right to the plumbing literally 4-6" from the end of the hose bib in the rear....

Safety ground vs. neutral

johnnatash4 wrote:

Can that screw handle it?

Are you possibly mixing together the functions of the safety ground versus those of the neutral line?

In normal correctly operating service all of the "grounding" current flows in the neutral line, not the safety ground.

And as to voltage the neutral line only differs from ground because of that return current, so if all is well it should be quite close to ground in voltage. Is it possible that that was what you determined with your tester?

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personal GPS user since 1992

tester

archae86 wrote:
johnnatash4 wrote:

Can that screw handle it?

Are you possibly mixing together the functions of the safety ground versus those of the neutral line?

In normal correctly operating service all of the "grounding" current flows in the neutral line, not the safety ground.

And as to voltage the neutral line only differs from ground because of that return current, so if all is well it should be quite close to ground in voltage. Is it possible that that was what you determined with your tester?

Well, the tester identifies an open ground, such as when a 3 prong receptacle is installed and there's no grounding wire. I'm used to attaching a 3rd wire which I believe is green.

I did not have such a wire to attach yesterday. Yet the tester lights up correct, as does a power strip. I do think I am referring to the safety ground...

Black is hot, white is

Black is hot, white is not(neutral), green is ground.

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Frank DriveSmart55 37.322760, -79.511267

Do modern power strips notice lack of safety ground integrity?

johnnatash4 wrote:

as does a power strip.

Interesting. It has been a long while since I bought a power strip, and none of mine had any means to indicate they were not happy with safety ground. How does this one show it is unhappy when it is?

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personal GPS user since 1992

Modern units have lots of bells & whistles

archae86 wrote:
johnnatash4 wrote:

as does a power strip.

Interesting. It has been a long while since I bought a power strip, and none of mine had any means to indicate they were not happy with safety ground. How does this one show it is unhappy when it is?

Good article at https://www.popularmechanics.com/technology/gadgets/g3062/be.... Many units today have built in GFCI and also wiring fault indicators.

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John from PA

Not a safety ground check, however

John from PA wrote:

Many units today have built in GFCI and also wiring fault indicators.

Very interesting.

But I don't think a single one of those units would report a fault in the safety ground.

GFCI units compare the current in the hot and neutral leg. They should be the same (complementary, actually). If not, they open up the circuit. No involvement of safety ground at all.

If one of these power strips shows "happy" on the ground fault light, it just means you are not sending current supplied by the circuit off to ground by a path other than the neutral line (a very bad thing, to be sure). It implies nothing about the safety ground integrity, unless I'm badly mistaken.

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personal GPS user since 1992

this

archae86 wrote:
johnnatash4 wrote:

as does a power strip.

Interesting. It has been a long while since I bought a power strip, and none of mine had any means to indicate they were not happy with safety ground. How does this one show it is unhappy when it is?

This is the one I use, as it seems to be decent for $11. Has a rating of 1440 joules, although I've read online that nobody has ever successfully filed a claim and gotten anything when equipment damaged. It has 2 green LEDs. One with a check mark indicates the power is on, and the other has an icon of ground. I do in fact have some outlets which a tester shows a ground fault, and when the power strip is plugged into those receptacles, the 2nd LED is not lit....

https://www.apc.com/shop/us/en/products/APC-Essential-SurgeA...

Interesting

johnnatash4 wrote:

I do in fact have some outlets which a tester shows a ground fault, and when the power strip is plugged into those receptacles, the 2nd LED is not lit....

https://www.apc.com/shop/us/en/products/APC-Essential-SurgeArrest-PE76W-7-Outlets-6-Foot-Cord-120V-White/P-PE76W

The APC user manual (short) for that class of strips has this to say about the meaning of the "Ground OK" LED being extinguished:

"The LED extinguishes to indicate that a wiring fault has been detected. Possible wiring faults include a missing ground, a hot neutral polarity reversal, or an overloaded neutral circuit. Discontinue use and have a qualified electrician correct the building wiring."

So, yes, they do say it is something beyond just what a GFCI detects.

Good luck getting your wiring fixed.

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personal GPS user since 1992

That may have been the

That may have been the smartest $2.18 you spent this week, possibly averting an electrical house fire or an electrical shock injury. You might take a look at other 30-year-old outlets you can see on the house.

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"141 could draw faster than he, but Irving was looking for 143..."

power strip safety

Long but valuable read on the hazards of older power strips with built in MOVs. https://forums.qrz.com/index.php?threads/entire-shack-shop-m...

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-Quest, Nuvi 1390T