OT: voltage on my ground rod

Bruce's answer was right on the money. It's not that unusual a problem, it is sometimes noticed by people with barefeet touching a water spigot, or in a shower where there is a slight difference in potential between the plumbing and the shower floor. The cause is usually related to voltage drop on the neutral, either on your side of the pole or on the distribution system.

Or in one case that almost threw me, a "neutral" out to the wellhead that really was a ground bonded to the box at a splice box in mid-run

- and open towards the main. Which was never a problem while the only neutral load out at the wellhead was the occasional power tool - the well pump was 240V, it didn't care a whit about the neutral.

But when they tried hooking up an outbuilding with constant 120V loads to the well line, suddenly people in the shower started noticing it...

No neutral, so it was going to 'ground', the wellhead was bonded, and was coming back on the cold water main after making three laps of the route. I was getting 6 to 10V AC between the closest shower faucets to the water heater and the floor drain. And when you turned off the well power, it went away...

Remember, folks: Just because you see a white green or bare wire in the box does NOT necessarily mean it's hooked up properly all the way as a neutral or ground. ESPECIALLY in rural areas like ranches and (ahem) summer camps where many DIY'ers have had a hand in the system.

In fact, up till the early 1960's, green was legally used as a hot conductor color - and I've gone out on a few calls where Mr. Handyman tied a hard short on a green circuit thinking it was the ground wire.

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Way before that there wuz "Ground Telegraph" in use. I remember reading how they would span rivers with it by sticking two rods into the ground (spaced a fair distance apart?) on each side of the river, applying a dc telegraph signal across the pair on one side and a sensitive receiving relay on the other.

Third pix down on left column here shows one:

Also, stuff on "earth batteries" makes inteesting related reading...

Jeff

I agree with everything you say, and given the right moisture conditions you CAN feel very low DC potentials. I recall, but don't want to repeat the experiment, getting a littl piece of some kind of foil candy wrapper in my mouth by accident and when it made contact with a mercury amalgam filling I felt quite a mini-zap from it inside my mouth.

And, don't let anyone con you into licking the terminals of a 9 volt "transistor radio" battery either, you can "feel" that REAL well.

I recall hearing that some people had dental appliances which, when certain parts touched each other, would create rectifying junctions and turn their mouths into "crystal sets". They could "hear" strong AM stations through the audio voltages impressed on their aural nerve system. I have no idea whether those claims were true or bullplop.

Jeff

This has nothing to do with ground(s) but is interesting phenomena that can be confirmed by any old "open wire" lineman. If you stand underneath a large multi-crossarm telephone lead you can hear a faint sound from hash generated by the inductive cross-talk of all the overhead circuits. Minute magnetic effects among all the wires is the cause. On a much larger scale, the conductors of large power systems where they come into close proximity must be rigidly anchored in place to keep them apart. This is also true with respect to the conductors in large motors and generators.

I had exactly this issue several years back at my parents house. I had

6 VAC to ground from the faucet in the basement. It gave a slight tingle in bare feet. Checked the bonding in the service panel, grounding rod etc., everything seemed okay. Next I went to the ground conductor on the pole in the front yard and got about 8 volts AC, so I started checking the grounds on each pole down the street and got higher readings of up to almost 20 volts as I approached the substation at the corner of our street. For a ground reference I was using a 3' rod stuck in the earth 15 feet away from the pole grounds. I think our electric company had a grounding issue at the substation. This was a fairly sizable substation - I don't know how big , but the transformers were bigger than the 4000KVA transformers we have at work for our ovens. Since I was using a relativly low resistance ground connection as my reference I don't think this was radiated or stray power I was seeing. The power poles in question had 33KV distribution lines on top, and lower voltage lines that the pole pots were tied into below that. Our electric company, PECO, said we had no problem at the time. I should note two other things our local PECO people did. This same location also had a sizable number of homes on an underground service as well. For some reason the neutral on the underground feed failed. Peco was called and to my surprize they ran a temporary neutral from the pole, accross two lawns, down the curb on the street and into the underground vault. This line remained for several years! Amazingly no one cut it with a mower or their car, as they could of be fried! Just a year ago I had to put in a sewer line to sell the property. PA one call marked the underground 4300 volt underground lines. Well guess what? PECO's info to PA one call was incorrect - there were two lines, not one, about a 4 feet apart - but only one was marked, the abandoned one. The live unmarked one was soon found by the backhoe operator - with a loud bang and flash! PECO was very appologetic when they arrived on the scene to repair the cable, but the operator could have been killed.

Ever seen shipboard welding? Pretty impressive to watch the fat cables slap against the steel deck as the welder strikes an arc.

Substation grounding and operator safety is usually taken very seriously. I've got a copy of the IEEE "Green Book" on power grounding and it has a whole chapter on the subject. The big concern is not so much steady state voltage differences, but the behavior during fault conditions.

During a severe fault, the substation "ground mat" might rise as much as 1000-

1500 volts above the nearby earth ground and much effort is put into making sure nobody comes between the two potentials.

All this talk about electrical "tingles" reminded me that amongst my collection of arcania I've got a medical "shock box" from the 19th century, made right here in Red Sox Nation.

Here it is, with a couple of its "application handles" and their lead wires:

Metal content: The lathe in the background is my olde Stark, which spent its salad days doing its thing at the Waltham Watch Company.

The shocker works off a single wet cell copper/zinc battery. It's just a stepup coil with a "trembler" interrupter (Like a buzzer operated by a current coil.)

The stepup coil has a core which is just a bundle of straight pieces of iron wire in a split brass tube which can be slid in and out to regulate the intensity of the "tingle".

I imagine that after o single "treatment" the patient would shout, "I is cured doc! I won't need to come back anymore!"

Here's a (poor) shot of the instructions glued inside the lid:

I cringe whenever I read the list of "application handles" available for it, particularly when I see that they included rectal and vaginal ones.

Jeff

On Sat, 19 Aug 2006 12:46:47 -0400, with neither quill nor qualm, Jeff Wisnia quickly quoth:

Wow, that reminds me of Nana, my grandmother on Mom's side, who had an old TENS unit. It was the size of a double-d flashlight and it had two wire leads with 1.5" x 2.25" leather pads on it. You'd wet the pads and put one on your chest (!) and the other on a sore muscle. When you hit the sore one, it would contract as you moved the pad back and forth. There was a wirewound rheostat in the top which would adjust the current, but it was a single frequency trembler like yours. I asked Mom what had happened to it when Nana died in 1988 but she couldnt' find it. I really wanted that thing. It worked very well; better than my new Brit TENS unit (though the new adhesive pads are a definite improvement over the wet leather jobs.)

That shop is WAAAY too clean, too.

As did Nana's, but they were D-cells.

Eek! One could redo that with lighting ot the side so they didn't have the flash bouncing off it, couldn't one, Jeff? ;)

I understand that nowadays, doctors use much larger anal probes called "endoscopes". The OUCH factor seems not to have changed much over the centuries. Vive le Marquis de Sade!

Jeff, you have something very amazing.

i

One time I had my van parked in a wet field nearly under a small cross country power line. When I touched the van I got a 60 Hz surprise. I checked with my Fluke meter and got 164 VAC between the ground and the van.

Get some flouresent bulbs and hold them up under a high tension line and touch the one end terminals of the bulb.....they will light up.

John

Aw, go on, try it. You get used to the twitching sensation in your tongue, and with a bit of experience can discriminate between a fresh and a so-so battery.

Ned Simmons

I had an old Stark lathe like that one. Big box of collets and some thread chasing things. One of the coolest features was a sort of milling attachment on the left end of the spindle, A small vise and x-y sliding fixture. You mounted the milling cutter in that end with the collets.

Thats how I test them.

Quite true. My first dental bridge, which lasted only a couple days before requiring extensive rework..would do that to me if I was working in a particularl part of town near a local radio station. Unfortunately the station was Mexican format...and having "Sabado Sabado!!!" echoing through my skull during the day (ad for a mexican swap meet on sunday) was a bit too much. Not to mention the Musica..station played traditional Ranchereo music...(think polka 24/7..umpa umpa umpapa umpapa......NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO!)

ahum...the dentist did some grinding and whatnot and it went away.

He knew Id kill him stone dead if he didnt fix it...he said he could see it in my eyes.... umpa umpa umpaumpaumpaumpapa......

Gunner

"I think this is because of your belief in biological Marxism. As a genetic communist you feel that noticing behavioural patterns relating to race would cause a conflict with your belief in biological Marxism." Big Pete, famous Usenet Racist

Jeez Gunner! You live down there and don't know Sabado! Sabado! means Saturday! Satrurday! ? If it was Sunday! Sunday! you would be hearing Domingo! Domingo!. ERS