modified GFCI

[JR.]

out_test_rpbg.JPG (59.79 KiB) Viewed 13323 times

Here is my first proof of concept outlet tester.

In the picture it is plugged into a dangerously miswired (RPBG) reverse polarity bootleg ground. Reverse polarity is generally harmless but when ground is bootlegged to what should be 0V neutral, but instead gets bootlegged to 120V the ground lug is now 120V too..

Most of the outlets in my house indicate single green for correct polarity open ground, the power to my bench is single yellow (line and neutral swapped),

The intersting thing is that the ubiquitous outlet tester sold in hardware stores will test a RPBG outlet and say it is OK.... . The hardware store tester is UL approved, but that doesn't mean it works, just that it won't catch fire or shock you.

JR

PS: 20+ SMD components that I hand assembled... I'm too old for this sh__

[emrr]

This is a very good thing to proof. Thanks JR.

[mediatechnology]

Very cool!

Maybe you need to combine this analyzer into a gizmo that "rearranges" the outlet to create a safe one.
If it doesn't have enough conductors to create a safe outlet or detects a fault in use it safety disconnects.

[JR.]

Very cool!

Maybe you need to combine this analyzer into a gizmo that "rearranges" the outlet to create a safe one.
If it doesn't have enough conductors to create a safe outlet or detects a fault in use it safety disconnects.

I posted schematics a few pages back of a more complicated smart outlet that combines a GFCI with a relay to completely disconnect power and ground if the wiring or ground current is not right. If course it would be possible to add yet another relay to flip the line/neutral polarity if backwards, but that by itself is not dangerous, Only the reverse polarity "combined with" a bootleg ground is dangerous.

Talking with professionals who routinely deal with squirrely power,,, they felt an automatic smart outlet that tolerates dangerously miswired outlets is the wrong solution. Dangerous outlets need to be taped over and then fixed,,, not used.

I like the relatively KISS tester that actually works...

My GFCI with stinger cap to current limit ground path current is also a rational solution for live sound back line.

JR

[JR.]

I have been ringing out my outlet tester, and discovered a flaw. My crude "ground present" LED was too sensitive. It would indicate a ground connection even when there wasn't one, if appliances with leakage to ground were plugged into that same outlet. (my Kitchenaid mixer leaks enough to the ground to light my ground LED.) Inexplicably my bathroom outlet also gave a false ground present indication.

The easy fix for this is to increase the ground current to swamp out any stray paths, but this could cause a different problem where it could trip a GFCI protected outlet..(if > 5mA gets diverted to ground and does not return to neutral to balance the GFCI it shuts down).

Of course I came up with a circuit solution, that I will not publish yet since I want to license this design to some company. If I keep giving away all the milk, who will buy my cow?

The ground present solution worked fine dealing with the leaky appliances in my kitchen, but the bathroom outlet still showed a ground connection. Today I opened up that outlet and found an inadvertent short between neutral and the metal junction box, causing an accidental bootleg ground. When I fixed that my original outlet tester worked correctly there too.

JR

PS: Maybe i should add fixing that outlet to my entropy thread,,, NAH

[ricardo]

The ground present solution worked fine dealing with the leaky appliances in my kitchen, but the bathroom outlet still showed a ground connection. Today I opened up that outlet and found an inadvertent short between neutral and the metal junction box, causing an accidental bootleg ground. When I fixed that my original outlet tester worked correctly there too.

Which shows the device is working as intended

[JR.]

The ground present solution worked fine dealing with the leaky appliances in my kitchen, but the bathroom outlet still showed a ground connection. Today I opened up that outlet and found an inadvertent short between neutral and the metal junction box, causing an accidental bootleg ground. When I fixed that my original outlet tester worked correctly there too.

Which shows the device is working as intended

Exactly.. It's sad how unreliable the common hardware store outlet tester is...

JR

[mediatechnology]

Today I opened up that outlet and found an inadvertent short between neutral and the metal junction box, causing an accidental bootleg ground. When I fixed that my original outlet tester worked correctly there too.

Wow. Could have just as easily been the hot shorted to the (potentially floating) metal box. Good thing you looked.

I wonder how many times makers of outlet testers have been sued because it tested good and wasn't.
I suspect not often.

[JR.]

Today I opened up that outlet and found an inadvertent short between neutral and the metal junction box, causing an accidental bootleg ground. When I fixed that my original outlet tester worked correctly there too.

Wow. Could have just as easily been the hot shorted to the (potentially floating) metal box. Good thing you looked.

Yes, and i am embarrassed to admit that I wired that outlet, actually I replaced a conventional outlet with a GFCI. The GFCI outlet was almost as wide as the junction box, but in their defense the line and neutral screws are recessed. I was sloppy, but may still buy a larger junction box. (another future project).

I wonder how many times makers of outlet testers have been sued because it tested good and wasn't.
I suspect not often.

I suspect you are correct. The mass market tester (GE) is UL approved, but that only means it won't catch fire. If a DIY electrician uses one and screws up (the cheap tester does not detect RPBG), I am not sure he has much recourse. Bootleg grounds even with correct polarity are not to code, because an open neutral line would then energize the ground through any appliances plugged in.

I would find it very interesting to hear UL in court explain their approval for a tester that clearly doesn't work, but they do not say that it works, only that it won't burn your house down.. I suspect a good lawyer could argue the indirect human safety hazard created by the inadequate tester.

Consumers ASSume the UL approval means more than it does.

JR

[Speedskater]

There are dual GFCI receptacles available with a low form factor. Designed to fit in older outlet boxes.