While most of the AR community may find this topic boring,
too technical,
unrelated to what AR is all about,
downright dangerous,
and/or "over-the-top,"----I want to do it anyway. It is primarily for all the Inspectors in the AR community. This is not one of those, "go-out-and-buy-some-test-equipment-and-try-this-at-home-type-blogs."
It has to do with un-grounded wiring in homes.
Sometimes homes have grounded-type wires run throughout the home, but the ground wire is either not connected to the devices (receptacles, switches, light fixtures etc), or the wire just simply isn't used---or even possibly disconnected somewhere. Homes wired in the early 60's often have this condition. This was when they first started manufacturing house wiring that included a ground wire, but there was no requirement to actually "use" the wire.
We will often see these ground wires just run back out through the back of the boxes where they are either twisted together and wire-nutted together, or they are merely cut off. Sometimes they were attached to the metal boxes sometimes they were not. We might see these boxes in unfinished basements or other partially finished areas of the home. Here are a couple of examples.
This becomes a problem for the inspector because it is difficult to check for reversed polarity of two-prong receptacles when the home has been wired this way. Both slots will read hot. In fact the entire area around the receptacle within 6"-8" of the receptacle might read "hot" with a voltage tester----we call this "Phantom Voltage" or "Induced Voltage." (I have written a couple of other blogs on this topic which might be of interest to those of you that have read this far in this one.)
This Phantom Voltage is high enough to set off a 90-volt "tick-tracer" (voltage indicator). The voltage will actually be the same as whatever the voltage of the circuit is. Because it is an induced voltage there is no actual amperage present so shocks are not an issue. For the inspector, "CONFUSION" is the issue, because of how all this induced current prevents testing of the device for polarity.
The following pictures demonstrate how the many parts of the receptacle and the surrounding wall test as "hot" with the voltage indicator.
Note that in the next picture, on the left, even the metal screw that holds the cover plate in place reads as "hot." Simply touching the metal screw with one's finger is enough to "cancel" the Phantom voltage allowing the inspector to use the tester normally to check for proper polarity of the receptacle.
Charles Buell
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Charlie - I know you said inspectors only but I was sucked in. YOU ARE very thourough - and I appreciate the knowledge you share here on AR! Maybe this guy should read up!
Carol, did Steve Smith send you that picture of himself from his radio days?
Pretty interesting information Charles. If a person were to put their tongue to that screw would they feel anything like you do when you put it to a 9volt battery?
Sean Allen
Bee,
You are a wimp. I like to play with 240 volts and above in outside settings while standing in the rain. Anyone seen the dryer? Darn, big problem with keeping it on the back porch is someone might shoplift it.
I did as you said. I didn't read it. But I'll bet it was a good blog! Electricity is more complex than Excel so I didn't go there.
Sean, unless it is actually "hot"---you would feel nothing----it would make a good picture though:)
Steve, you sure put your finger in funny places.
Barbara, you can't fool me:)
Well, you know I HAD to read this post after the instructions said not to do so. But it's OK, because I am a very grounded person...
Margaret, These kinds of titles always get people to disobey:)----that is what they are for!
Charlie,
You basically fooled these good folks into breaking the rules. Nice guy.
Phantom voltages can drive you nuts Charles... It is really interesting how just grounding can get rid of it. That is the main reason that I really hate the old 2 wire convention...
Charles, You are brave to put your finger on the outlet cover screw. Have you ever had your hair redone like the guy in Carols picture because the outlet was in fact hot?
Michael, with this little trick it sure gets a little less frustrating:)
James, some part of me would have to be touching something grounded when I touched the screw to get a shock----otherwise there is no danger from touching it even if it was actually hot. It would actually be quite difficult. One time I found a receptacle next to the bathroom sink that someone had hooked the hot wire to the green screw and the cover plate screw was indeed hot. The proximity of the cover plate screw and the metal faucet and plumbing made it a life threatening situation.
Charles another good post. I'm glad you have a digital camera handy to show us your work. You must get a new post out of every inspection. Thanks again...
Charles - Just goes to show how well people follow instructions. Out of 13 answers you had 3 inspectors. Good post.
Last spring I had a tic testor that decided it would indicate everything BUT hots. Interesting way to do things. If it didn't light and tic-tic-tic it was hot (well not all the time). Obviously, bought new.
Charlie B,
I agree with your comments above. In the years I have known you nobody has ever referred to you as well grounded.
Paul, it is pretty rare to do an inspection and not come away with some idea for a blog.
Jack, I kind of figured with the title that that would happen.
Steve, thanks for the compliment:)
No problem Charlie. I just wish you were not a squirrel hater.
Charles- I almost didn't read this one b/c I was scarred that you would zap me for intruding (not being an inspector and all) any way I like what you said to Paul, and would like to add: "It is pretty rare to do ANYTHING anymore and not come away with some idea for a blog.
Think I am going to write about reading comments- no wait, write about crashing private peer groups- no wait--write about ....... ah be good cheryl (not an inspector but a fan of their group)willis
Steve, we have shared many a grilled squirrel together----how can you call be a squirrel hater?
Cheryl, consider yourself "zapped"---and keep coming back:)