Reverse Polarity Bootleg Ground Testing

[Steve L. Hipps]

3 light testers

3 light testers

I ran into this last week in a home that had reversed polarity and bootleg ground, they had destroyed 2 TV's.
I notified Ideal about the situation and they responded that they were aware of the situation but had no plans to change anything.
My concern is for the home inspectors and the average homeowner that may use these and think that the outlets are correct.

 

[kwired]

Exactly right.... and nothing exists like what you describe.

In fact, what got me going on the 3-light tester problem was that I was thinking about building a 3-light tester using 100-watt light bulbs to load the H, N and G wires a bit (to prevent reading hi-z grounds as good) and then noticed from the schematic they can't identify RPBG outlets. I'm really tuned into bootleg grounds with reverse polarity since I just remodeled the kitchen in my 1926 built house, and a lot of the wiring was sill K&T. I'm removing all the K&T room by room as I re-mod and running new NM wire back to the service panel, which I'll update sometime this fall. But in the meantime, I've found many bootleg grounded outlets in my house, which were most likely installed by "the TV guy" who owned it 30+ years ago. About 20% of these bootleg grounds were reversed polarity, at least one was in the kitchen without a GFCI. Yikes!!!!

I've seen this exact sort of thing in the bars and churches I've played and engineered sound in over the last 40 years or so, but never had to chance to tear any walls open. But now I have examples all over my house for testing, and as I open up the walls for the re-mod get see what was really done. Sort of a test lab in my wife's kitchen, which she was not too happy about during the re-mod, but now that it's done she's very happy with it, especially when I explain the safety aspect.

What would make the most sense for a quick and better 3-light outlet tester would be for a manufacturer to install an NCVT inside a 3-light outlet tester connected to its ground pin. It would capacitively couple to the sides and pick up the ground plane of the person holding the tester. That will give you a 4th light (and beeper) that would indicate when the outlet ground/neutral was hot. As you surmise, nobody is going to run a 4th lead to a known ground, unless they're being paid to do it (as in an electrician).

I'm guessing somebody could build and sell this 4-light outlet tester in the $25 range (or even cheaper) since it's just a $5 neon tester married to a $15 NCVT. I've been studying Outlet Testers and Ground Loop Impedance Testers from every manufacturer I can find, and have never seen anything like it, but a 4-light outlet tester that references ground via a NCVT is something a sound tech or musician could be taught to use (I think).

Any thoughts or feedback on this?

Actually if one were to make a tester with a 4th lead that connects to a known ground it would be easy to make it detect bootleg grounds from the neutral also. If you load the neutral with a test load there should be voltage drop between neutral and ground if they are separate conductors. Now the shorter the distance to where the neutral/ground bond occurs the harder it becomes to measure the drop as it will be less.

 

[jmsokol]

Actually if one were to make a tester with a 4th lead that connects to a known ground it would be easy to make it detect bootleg grounds from the neutral also. If you load the neutral with a test load there should be voltage drop between neutral and ground if they are separate conductors. Now the shorter the distance to where the neutral/ground bond occurs the harder it becomes to measure the drop as it will be less.

That's exactly how testers like the INSP-3, SureTest, and CT-70 work. They fire a little current down the ground and neutral legs and will blink at you if there's too low impedance between the G and N contacts. However, none of these $200 to $300 testers can tell the difference between a CPBG (Correct Polarity Bootleg Ground) and a RPBG (Reverse Polarity Bootleg Ground). I have all three of those testers on my bench, and tried them out on my RPBG test rig. They will notify you there's a bootleg ground, but not that the ground/neutral is hot. They need a 4th lead or built-in NCVT in order to reference earth.

Pretty interesting, isn't it?

 

[kwired]

That's exactly how testers like the INSP-3, SureTest, and CT-70 work. They fire a little current down the ground and neutral legs and will blink at you if there's too low impedance between the G and N contacts. However, none of these $200 to $300 testers can tell the difference between a CPBG (Correct Polarity Bootleg Ground) and a RPBG (Reverse Polarity Bootleg Ground). I have all three of those testers on my bench, and tried them out on my RPBG test rig. They will tell you it's a bootleg ground, but not that the ground/neutral is hot. They need a 4-th lead (or built-in NCVT) to reference earth.

Pretty interesting, isn't it?

Interesting - I guess so, new information - no. It has been known for a long time these will not tell you if the bootleg is on the hot conductor. People that are not electrical professionals just don't know any better, same with unusual circumstances with a non contact tester.

Sound guys that are part of a 'big band' may have electrical knowledge. The little bands and DJ's are the ones that not only perform but are also the sound technicians, equipment set up and, everything else and may know very little electrical.

 

[jmsokol]

Why I started this thread...

Why I started this thread...

I ran into this last week in a home that had reversed polarity and bootleg ground, they had destroyed 2 TV's.
I notified Ideal about the situation and they responded that they were aware of the situation but had no plans to change anything.
My concern is for the home inspectors and the average homeowner that may use these and think that the outlets are correct.

This scenario is EXACTLY why I started this thread. I've already contacted Amprobe, Extech and Ideal telling them their fancy Ground Loop Impedance Testers can't detect an RPBG, and have had limited positive feedback. Check out http://www.youtube.com/noshockzone where I have demo videos of the INSP-3 (Amprobe) and SureTest (Ideal) failing to find RPBG. I'll do a video on the CT-70 (Extech) next week.

They are certainly a step up from my antique (and still very cool) Woodhead GLIT since they also find bootleg/false grounds. But don't identify hot neutral/ground wiring.

Please forward this thread to your contacts at Amprobe, Ideal and Extech. Maybe it will make a difference.

 

[kwired]

I ran into this last week in a home that had reversed polarity and bootleg ground, they had destroyed 2 TV's.
I notified Ideal about the situation and they responded that they were aware of the situation but had no plans to change anything.
My concern is for the home inspectors and the average homeowner that may use these and think that the outlets are correct.

That does happen. Can also happen with a multimeter if you don't know what to check. There is no real way to detect bootlegged ground by only testing the pins of the receptacle - you need a known ground as a reference to test to for even beginning to perform this test, then would come loading the circuit to verify there is a potential between neutral and ground. Ideal is not the only one that makes these devices and not the only one that is aware of this possibility. I would not be suprised if there is some literature that comes with these testers to indicate that there may still be unique situations like what is described here - they do this to help lower any liability they may end up having, or CYA.

 

[jmsokol]

Interesting - I guess so, new information - no.

Perhaps field EE's understand this and possibly good inspectors/electricians, but I talked to the tech departments at Amprobe and Extech a few months ago about this RPBG issue, and it was news to them at the time. Maybe they all forgot???

But certainly your average DIY guy who buys a $5 outlet tester at a big box store doesn't have a clue....

 

[K8MHZ]

This is probably one of the best threads I have ever seen here.

Thanks Mike!

Welcome to our forum.

I hope you stick around. We need people that understand test equipment and can explain it like you do.

Very well done!

 

[jmsokol]

This is probably one of the best threads I have ever seen here.

Thanks Mike!

Welcome to our forum.

I hope you stick around. We need people that understand test equipment and can explain it like you do.

Very well done!

Thanks very much...

 

[K8MHZ]

Sound guys that are part of a 'big band' may have electrical knowledge. The little bands and DJ's are the ones that not only perform but are also the sound technicians, equipment set up and, everything else and may know very little electrical.

Absolutely not. All they do, and this is the same for the 'electrician' is plug stuff in. I was an electrician working out of the local IATSE hall in the early 80's. All I was allowed to do was plug stuff in and on occasion fix the ends of extension cords. We did big shows like Cheap Trick, Guns n Roses and, hold on to your hat, Sesame Street. We needed an electrician to bring in a transformer on one show and connect it. The local IBEW hall was called and they referred an IBEW union electrician to come out. I got to help, but 'real' electrical stuff done on larger stages is done by local electrical contractors, not the roadies.

 

[K8MHZ]

I just did an actual test and found that hot / neutral reversed with open ground only shows 'open ground'.

The ONLY way the testers will properly indicate a hot / neutral reversal is if there are three wires and the ground wire is in the proper place.

So....what happens when we push the GFCI test button?

Test 1 - Hot / neutral reversed, no ground. Tester shows only 'no ground'. Pushing the GFCI button indicates 'hot / neutral rev.

Test 2 - Correct polarity, no ground. Tester shows 'no ground. So far so good, but pushing the GFCI button still indicates 'hot / neutral rev.' when they are not.

 

[jmsokol]

I just did an actual test and found that hot / neutral reversed with open ground only shows 'open ground'.

The ONLY way the testers will properly indicate a hot / neutral reversal is if there are three wires and the ground wire is in the proper place.

So....what happens when we push the GFCI test button?

Test 1 - Hot / neutral reversed, no ground. Tester shows only 'no ground'. Pushing the GFCI button indicates 'hot / neutral rev.

Test 2 - Correct polarity, no ground. Tester shows 'no ground. So far so good, but pushing the GFCI button still indicates 'hot / neutral rev.' when they are not.

Yup, without a Ground for reference a 3-light tester can't know if the Hot and Neutral are reversed. Swapped Hot/Neutral polarity isn't really that big a deal (although against code and should be repaired immediately) since all modern appliances and electronics use power transformers to isolate the chassis from the "Neutral" line. But on the days of AC/DC radios, there were no power transformers and the incoming Neutral wire was tied directly to the chassis. A swapped hot/neutral would electrify the chassis at full line voltage and amperage. Yikes!!!!

I think those little 3-light "ice-cube" testers are close to worthless for real troubleshooting and testing.

 

[kwired]

Sound guys that are part of a 'big band' may have electrical knowledge. The little bands and DJ's are the ones that not only perform but are also the sound technicians, equipment set up and, everything else and may know very little electrical.

Absolutely not. All they do, and this is the same for the 'electrician' is plug stuff in. I was an electrician working out of the local IATSE hall in the early 80's. All I was allowed to do was plug stuff in and on occasion fix the ends of extension cords. We did big shows like Cheap Trick, Guns n Roses and, hold on to your hat, Sesame Street. We needed an electrician to bring in a transformer on one show and connect it. The local IBEW hall was called and they referred an IBEW union electrician to come out. I got to help, but 'real' electrical stuff done on larger stages is done by local electrical contractors, not the roadies.

I didn't say they are electricians, but fair enough, most of these people that connect things for temporary events may call themselves electricians but they are just gurus that know how to plug things in and do a little swapping and resetting until it all works out. I hate providing temporary power for anyone that wants more than just a few 15 or 20 amp 120 volt receptacles. 99% of the time they want a 50 amp 125/250 3 wire receptacle (3 wire range receptacle) If I put it on GFCI like it generally is supposed to be if temporary they will trip GFCI. I will even put 4 wire receptacle in for them and they will try to make an adapter for 4 to 3 wire - still trips GFCI. You can't explain to them why what they have is wrong. They don't want to hear it. They just tell you they have been using what they have for years never a problem. It is not going to be a problem on my temporary wiring either - use the right thing or get someone else to hook it up wrong for you.

You ever have Sesame Street open show before Guns and Roses?:lol:

I think those little 3-light "ice-cube" testers are close to worthless for real troubleshooting and testing.

Like any other test instrument, you have to know what its limitations are.

I can't believe some engineers and other experienced people couldn't figure out that they will not indicate equipment ground bootlegged from hot conductor will not be indicated. The thing has no reference to "true ground" to know any better, all it knows is the relationships between the three pins, if it reads correct voltage range between the right places that is all it was designed to indicate. You can come to same conclusions with a multimeter if you never measure to a "true ground".

 

[K8MHZ]

The scary part is that these things are sold by the thousands to home owners that don't have a clue and see no reason not to trust them.

 

[jmsokol]

I can't believe some engineers and other experienced people couldn't figure out that they will not indicate equipment ground bootlegged from hot conductor will not be indicated.

And yet, they dont!!! If you want to see something really interesting on ProSound Web in the sound tech forum, take a look at this thread: http://forums.prosoundweb.com/index.php/topic,137760.0.html

My engineering buddy at Whirlwind alerted me to it when someone posted that a 3-light tester would indicate an outlet was wired properly. This was after it caused an interconnecting XLR cable between two pieces of gear to turn red-hot and melt down. I jumped right into the middle of the thread and showed them the limitation of 3-light testers and dangers of Reverse Polarity Bootleg Grounds. Now, these are not a bunch of kids, but professional sound technicians doing gigs in clubs and bars. Now if you're an A-List act (or possibly Sesame Street ) you'll get a licensed electrician to provide power on cam-locks which is "almost" always correct. But your own stage crew will distro it from there using something like I have pictured below.

However, there must be 100 club/bar gigs for every single A-List gig out there, perhaps even more like a 1,000:1 ratio. I do know there are 400,000 churches in the United States (nearly every one with a PA system and most with some sort of music), and at least that many bars (I use the ratio of one bar per church since the Musician's Union can't even give me a number), plus who knows how many hotels with club bands and conference rooms that have A/V hookups. That's a lot of sound systems hooked up every week and weekend by musicians and sound technicians who know next to nothing about electricity. There has to be millions of musicians plugging into unknown power sources every week. Yikes!!! And most of them are not concerned at all about getting shocked when they play. They think it's all part of the gig. (No kidding)

So next time one of you step up to a karaoke mic, check first to make sure it's wireless. I don't trust hard-wired mics in clubs...

 

[kwired]

The scary part is that these things are sold by the thousands to home owners that don't have a clue and see no reason not to trust them.

I am even more afraid of anyone that trusts non contact testers. Non contact testers work best for identifying open/missing equipment grounding conductors, doesn't mean they will necessarily catch every one but are an easy way to find this problem. It is easy test, turn light switch on and hold tester near metal surfaces of luminaire that are supposed to be grounded. If the thing beeps or squawks like it does for voltage indication - the part you are holding it close to is not grounded. 99% of the time it will be right when it does this. Had one only once that said no ground yet we could not find why it indicated that because we made sure it was grounded and it still didn't change its mind.

I don't trust non contact at all for verifying no voltage before working on something, even when testing a known working source first they still can mislead you.

 

[jmsokol]

I don't trust non contact at all for verifying no voltage before working on something, even when testing a known working source first they still can mislead you.

I'm not advocating the use of NCVT's to confirm the power is off before you work on wiring, only to use them as a quick check for electrified mics, guitars, appliances and RPBG's.

Also, if you get a NCVT near a double-insulated appliance that doesn't require a ground plug, they'll usually squawk since there's typically 60 volts on the appliance you'll soon be picking up in your hands. That's due to capacitive and inductive coupling internally. But since by definition a double-insulated appliance "can't" source enough current for you to feel, let alone get electrocuted, they're deemed safe and can be UL approved. I still get a little worried standing on the wet ground with my non-grounded/double-insulated circular saw... but I suppose it's better than using a old "needs a ground" saw with a cheater plug on the extension cord.

Nope, a high quality meter is still your best friend. That's my final test before I reach into a presumably "dead" panel.

 

[K8MHZ]

I am even more afraid of anyone that trusts non contact testers. Non contact testers work best for identifying open/missing equipment grounding conductors, doesn't mean they will necessarily catch every one but are an easy way to find this problem. It is easy test, turn light switch on and hold tester near metal surfaces of luminaire that are supposed to be grounded. If the thing beeps or squawks like it does for voltage indication - the part you are holding it close to is not grounded. 99% of the time it will be right when it does this. Had one only once that said no ground yet we could not find why it indicated that because we made sure it was grounded and it still didn't change its mind.

I don't trust non contact at all for verifying no voltage before working on something, even when testing a known working source first they still can mislead you.

All NCVTs are not created equal. The first ones I used sucked. It was a few years before I tried another and it was totally different.

Buy a Greenlee GT-11 and play with it for a while. I think they are the best, and the most discerning.

I just tested a 2 wire circuit with an adaptor connected to a three wire extension cord and the GT-11 had no problem indicating the hot and not the others. I have had NCVTs that would indicate on all conductors, or none. Even when one was hot. I think the last one I had that did that was a GB. So far, the GT-11 has never missed a hot.

Then comes the TR receptacles that require all prongs to go in to access the terminals. It's hard to read a hot when you can't get passed the door.....:rant:

But, our friend the cube tester can get in there!

 

[K8MHZ]

I still get a little worried standing on the wet ground with my non-grounded/double-insulated circular saw... but I suppose it's better than using a old "needs a ground" saw with a cheater plug on the extension cord.

I know just what you mean and am glad for in line GFCI protection.

 

[jmsokol]

All NCVTs are not created equal. The first ones I used sucked. It was a few years before I tried another and it was totally different.

Buy a Greenlee GT-11 and play with it for a while. I think they are the best, and the most discerning.

I just tested a 2 wire circuit with an adaptor connected to a three wire extension cord and the GT-11 had no problem indicating the hot and not the others. I have had NCVTs that would indicate on all conductors, or none. Even when one was hot. I think the last one I had that did that was a GB. So far, the GT-11 has never missed a hot.

Then comes the TR receptacles that require all prongs to go in to access the terminals. It's hard to read a hot when you can't get passed the door.....:rant:

But, our friend the cube tester can get in there!

Here's a video of me testing an outlet for polarity and hot ground using a Fluke 1AC-A1-II which is rated for 90 to 1,000 volts. Fluke's low-voltage version is too sensitive to differentiate between the hot, neutral and ground contacts on a receptacle, and will beep anywhere near a live outlet.

http://www.youtube.com/watch?v=jF3Ntoa8ab8&feature=plcp

I didn't make this video for the trades, but rather for the RV owner who plugs their trailer or coach into a new and unknown receptacles at campgrounds every time they go camping.