Two houses were affected after a tree trimming company made a small mistake. One where a man was electrocuted while in the shower, and another where the cable box went up in smoke.

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What really drives us crazy is when we are able to determine beyond a doubt that the reason for a problem is improper grounding of the rack, and the custom installer thinks we are just blowing smoke. Eventually we are able to persuade them to try grounding the rack, and the problem goes away like magic. I am just amazed how many installers don't learn some of the fundamentals of electricity and electronics.

By the way, if you are reading this, then you are probably not one of the installers that doesn't get grounding.

In that case, you might want to require your own trainers to talk about this, even if only briefly. I went to a JAP training session last month and they never mentioned it, which makes a dangerous assumption.

For that matter, I think all of the manufacturers should mention this because, as you wrote, not enough installers know the importance. However, I think you might also make the point to company owners and managers- they're the ones who send people to be trained, or not. It's in everyone's best interest that this be done properly, but there's not enough dialog about it.

There hasn't been a proper grounding thread in a while. Always eager to learn more about grounding, and to hear others' perceptions.

I'll mention I that guy in the shower was shocked because the house was grounded.

Your word "think" did not appear. Please stick around long enough to read your own posts! What you wrote doesn't make sense until the Quote window is open.

By the way, I must be one who doesn't understand grounding, and/or the TV article does not present the situation properly.

A power line hit the ground. The ground must not be bone dry; that's normal, so at that place you can measure a voltage actually in the ground, decreasing with distance from the wire... unless there's a pipe nearby. That pipe will have a lower resistance than the soil, so will act as a conduit (good term!) for the raised voltage, taking it into the house.

The guy who got a shock touched a pipe, probably connected to one that passed near the wire on the ground -- and BECAUSE HIS DRAIN WAS GROUNDED, he got a shock.

A cable grounding rod, located near where the wire went down, would similarly be at a potential above ground, and could feed current into the cable system to... wait for it... it's about to be here... a properly grounded cable box, which would then fry.

Neurorad is real close, I think. I'll bet the guy got a shock because his water pipe was at a voltage above normal ground, and the shock was from his pipe through him to the drain... often a metal pipe, but not connected to ground where the water pipe is connected. Actually, the guy would not have gotten a shock if his water pipe had been connected to his drain pipe system -- and who does that?

From the video:


First, there is zero reason for him to mention galvanized pipe. Copper pipe would have probably delivered a heftier shock. The rest of what he says does not support either the guy's shock or the cable box fire.

After that, the article says several homes were without power, but not once was proper or improper grounding, or checking for good grounds, mentioned.

This fire and this shock happened because things were grounded and because shit happens.

This is probably the most ignorant response I have ever heard. Amperage is looking for a return to ground or earth as some call it. Always takes the path of least resistance. Improperly grounded systems will perpetuate your tales of shock.

Things cannot be grounded properly if shit happens.

You may not be as informed as you think you are. And you don't give a shot at explaining why the guy in the shower got a shock.

You have made zero reasonable statement until you explain what happened in technical detail.


Absolutely. And that is why A GROUND caused this situation!

(I'm going to say "dirt" below where when I don't mean the generic electrical term "ground.")

Dirt has a much higher resistance than pipe. If a live wire hits the dirt, the dirt at that point is raised to the voltage of the downed wire. The voltage of the dirt decreases as you travel away from the point of contact. A pipe that goes through this area will make a situation analogous to an analog volume control. The downed wire is the hot side of the VC. The ground side of the VC is some distance away where the dirt is at the same potential as the dirt two blocks away: GROUND. The pipe is like the wiper of the VC, in contact with the dirt when the dirt is at some voltage higher than zero but, because of the voltage gradient in the dirt, it's at some voltage lower than the downed wire. But still possibly fatal.

So the output wire of our volume control, which is the pipe, goes into the house. Sure, it goes through dirt on the way to the house, which drains off some of the energy, but the dirt has much higher resistance than the pipe, so the pipe still is at a higher potential than the dirt... and when it enters the house, it is not at ground potential. It's hot at some level.

Now the guy is in the shower. There's a drain. He steps on it. It's connected to drain pipes, which go to ground separately from the water pipes. Chances are nearly nil that the drain and supply have zero ohms between them, so there's a voltage difference. He touches the faucet, which is connected to the cold water pipe. Thus, shock.

Note that if the drain had not been grounded, or had been bonded to the cold water pipe, there would not have been any shock.


That is completely true. That's not what happened here. The guy could only have gotten a shock in the shower if he touched something grounded and something hot at the same time. The pipe was hot and the drain was ground.

Now stop saying I'm being ignorant and explain the details of this your way. I think you don't have a sensible explanation but I'll agree with you if you do. This is not name calling, it's science.

This.

A power line hit the ground. The ground must not be bone dry; that's normal, so at that place you can measure a voltage actually in the ground, decreasing with distance from the wire... unless there's a pipe nearby. That pipe will have a lower resistance than the soil, so will act as a conduit (good term!) for the raised voltage, taking it into the house.

The guy who got a shock touched a pipe, probably connected to one that passed near the wire on the ground -- and BECAUSE HIS DRAIN WAS GROUNDED, he got a shock.

[Link: en.wikipedia.org].

I would look at an open neutral before I made that broad statement. I didn't mean to chuck insults Ernie :). Just an EE trying to be rational. Sorry I got you wound up.

Yes, I improperly omitted the word 'think':

I'll mention I that guy in the shower was shocked because the house was grounded think.

That guy was probably shocked because the house was properly grounded to a cold water pipe.

And probably had galvanized pipes for the drain. Thus why he had a shocking experience in the shower. Still points to an improper ground, as the drain pipes should have been grounded with the cold/hot water pipes as well.

If the drain pipes were PVC or ABS or whatever they use now a days, the cold/hot water pipes that became electrically hot, wouldn't have affected him at all. Unless the water acted as the "ground". But even on a first floor house, that pipe has to go down a foot or two, to which point there won't be a continuos stream of water to reach the ground.

KOT

Wow... I don't want to wade in too deep here,.. but need to point out at least one thing that is important to know...

NEC requires earth ground to be bonded to all pipes, wires, etc., at the point of entry to a building. There would be a ground strap bonding the water, sewer, gas, electric, etc. Everything must be bonded together to avoid the scenarios described in a few posts here.

There was very likely a problem in the home to begin with.

If water and sewer were not bonded together (along with the power) it would make for a VERY dangerous situation, regardless of downed lines.

My house had a ground problem and something else wrong and I would get shocked in the shower all the time. My whole setup got fried to. It took the electrician almost a month to figure out the problem and fix everything. He replaced all the switches and plugs near the shower, swapped the breakers to gfis'. I had to take a bath with a bucket so I wouldn't shock my self.

He ran a new ground wire for the breaker panel and when he was tying it into the ground round it turned out to be a piece of rebar only about a foot deep. He replaced it with a like a six foot ground rod. It turned out that the main wires from the Utility pole got loose inside the meter box and was shorting out against the box but since the ground wasnt good it passed about 60 volts thru everything hooked up to ground.

Reminds me a bit of the Mythbusters episode where they wanted to test if a lightning strike could actually shock/kill someone talking on the telephone.

All depends when the house was built though. The house that used galvanized pipes was probably built before a time that NEC required all pipes to be bonded.

I know that my drain pipes aren't bonded. Mainly because their all ABS, can't really bond plastic.

I do recall from my electrical school, 2010, that a hot tub's drain has to be bonded. So that tells me that the hot tub's drain pipes, by nature of this code, are made of metal of sorts.

KOT