shocking bath tub fixtures - literally

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hj

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neutral

In this case the neutral had failed, and the "ground wire" was the metal casing from a piece of BX the builder had laying around. It was steel so it rusted away and the hot water line, including the heater became the neutral. When the union was disconnected all the power in the house became 240 volts and anything on an unbalanced circuit, which is usually everything, that was turned on burned out. Working in Chicago with all the DIY landlord repairs, you quickly learned NEVER to separate pipes with your hands. You hit them with a hammer or wrench and watched for sparks.
 

Brother

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In the Seattle area, a plumber cut a water main to a home on a repipe in the crawl space, and since it had been the ground, he then became the ground.
It killed him.


Terry, do you have a link to this article, or other info that i could read on this??
 

Billy_Bob

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FYI - I searched google.com for the words...

plumber electrocuted

...and it seems this has happened quite a bit.
 

Ladiesman271

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Actually the water main wasn't the ground, but the grounded conductor, aka neutral, current does not seek the ground (earth) it seeks source in which it arrived, (transformer at street) the earth plays no role in an electrical system, other than we try to protect our system from higher voltages and lighting strikes. thats the only reason why we drive ground rods, Hope that helps.



That is not what it says in my 1996 NEC handbook!
 

hj

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ground

the earth plays no role in an electrical system, other than we try to protect our system from higher voltages and lighting strikes. thats the only reason why we drive ground rods,

Interesting. Back in the dark ages the neutral WAS called the ground. But if the ground is only for higher voltages and lightning, I guess MILLIONS of dollars are being wasted putting ground terminals on appliances and wiring ground circuits inside houses when they are protected from lightning and higher voltages. In fact if it were just a lightning thing, the ground circuit inside the house would deliver the lightning strike to, and through, the house. In those days, the plumbing systems were all metallic, and it was part of the grounding system. Then as plastic became more prevalent, those houses had a lable in the power panel, "NON METALLIC WATER SUPPLY", and a ground rod, or two, was installed. Finally, rather than guess at what kind of material was being used, and since DIY repairs with plastic could interrupt the path, all houses were attached to a ground rod.
 
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JWelectric

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Hj

What so many calls the neutral today is the grounded conductor. We also have a grounding conductor and well as a grounding electrode conductor. Boy this electrical stuff sure has a lot of grounding going on doesn’t it?

The grounded neutral conductor or what is called the neutral conductor (ARTICLE 200 Use and Identification of Grounded Conductors) is connected to earth at the utility transformer as well as at the service point at the building being served.

The sole purpose of connecting this conductor to earth is;
250.4 General Requirements for Grounding and Bonding.
The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.
(A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

Using Ohm’s law one can see that a ground rod that complies with 250.56 won’t open a 15 amp breaker.
120 volts divided by 25 ohms equals 4.8 amps

But should the primary of the transformer short to the secondary of the transformer it will open the overcurrent device at the transformer primary which in most cases will be less than 20 amps.
At my house the primary is supplied by 13,000 volts but some are supplied by 7200 volts. Using ohms law it is easy to see that the overcurrent device for the primary will open in the event of a short
7200 divided by 25 ohms equals 288 amps

As has already been pointed out the grounding electrode plays no role in the function of an electrical system.
What causes the fuses and breakers to operate in the premises wiring is the bonding of the equipment grounding conductors to the grounded neutral conductor at the service. This gives a low impedance path back to the source to allow the overcurrent device in the premises wiring to operate.

250.4(A) (5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.
 

Furd

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HJ, you may be an excellent plumber and pipefitter but you are not an electrician or an electrical engineer.

It doe not matter WHAT something might have been called by the average person in the dark ages, what matters is the TRUTH! The truth is that there was NO ELECTRICITY in homes during the dark ages. Now if you were trying to be cute and meant during the early days of electricity in homes, businesses and industry then you are STILL wrong. In the early days BOTH conductors were independent of a connection to the earth and BOTH conductors were often fused. Eventually it was determined that connecting one conductor to the earth could limit the voltage induced upon wiring due to lightning strikes.

The EQUIPMENT GROUNDING system installed today has NO RELEVANCE to the groundED conductor of the electrical distribution system OTHER THAN to provide for a low impedance path from a so-called "hot" conductor back to the SOURCE of the electrical energy and in the process cause a (relatively) high current to flow on the "hot" conductor, through the overcurrent protective device (fuse or circuit breaker) and that OCPD will then open the circuit. The EQUIPMENT GROUNDING conductor does not do its job because it is connected to the earth, in fact it would likely NOT do its job if connected only to the earth. The EQUIPMENT GROUNDING conductor is connected to the groundED conductor of the electrical supply system, the so-called "neutral" conductor, AT THE SOURCE OF THE ELECTRICAL ENERGY, i.e. at the service entrance to a structure. The equipment grounding conductor and its function is NOT predicated on the presence or absence of metallic water piping, ground rod or the electrical service anywhere being connected to the earth. Having the electrical service connected to the earth AND also having other items that may be in contact with the earth such as metallic water, sewer and yes, even gas piping, along with any steel used in the building ENHANCES the safety of the entire electrical system by providing a low impedance return circuit to interrupt the flow of electricity during a fault condition.
 

Chris75

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the earth plays no role in an electrical system, other than we try to protect our system from higher voltages and lighting strikes. thats the only reason why we drive ground rods,

Interesting. Back in the dark ages the neutral WAS called the ground. But if the ground is only for higher voltages and lightning, I guess MILLIONS of dollars are being wasted putting ground terminals on appliances and wiring ground circuits inside houses when they are protected from lightning and higher voltages. In fact if it were just a lightning thing, the ground circuit inside the house would deliver the lightning strike to, and through, the house. In those days, the plumbing systems were all metallic, and it was part of the grounding system. Then as plastic became more prevalent, those houses had a lable in the power panel, "NON METALLIC WATER SUPPLY", and a ground rod, or two, was installed. Finally, rather than guess at what kind of material was being used, and since DIY repairs with plastic could interrupt the path, all houses were attached to a ground rod.

Look, if you dont understand it, then ask, but dont rant on something you just dont understand, I will answer any question you you ask. not trying to be an ass, just trying to educate. as hard as it is... :rolleyes:
 

Ladiesman271

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Here is the quote from my NEC Handbook.

"It is imperative that Code users be familiar with the definitions in Article 100, especially those terms associated with this article (250). Specific words to to be aware of are the "grounded conductor", "equipment grounding conductor," and "grounding electrode conductor."

Grounding can be divided into two areas: system grounding and equipment grounding. They are kept separate from each other except at the point where they receive their source of power, such as at the service equipment or a separately derived system.

Grounding is the intentional connection of a current carrying conductor to ground or something that serves the place of ground. In most instances, this connection is made at the supply source, such as a transformer, and at the main service disconnecting means of the premises utilizing the energy.

There are three basic reasons for grounding:

1. To limit the voltages caused by lightning or by accidental contact of the supply conductors with conductors of higher voltage.

2. To stabilize the voltage under normal operating conditions. This maintains the voltage at one level relative to ground, so that any equipment connected to the system will be subject only to that potential difference.

3. To facilitate the operation of overcurrent devices, such as fuses, circuit breakers, or relays, under ground fault conditions."
 
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Chris75

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Here is the quote from my NEC Handbook.

"It is imperative that Code users be familiar with the definitions in Article 100, especially those terms associated with this article (250). Specific words to to be aware of are the "grounded conductor", "equipment grounding conductor," and "grounding electrode conductor."

Grounding can be divided into two areas: system grounding and equipment grounding. They are kept separate from each other except at the point where they receive their source of power, such as at the service equipment or a separately derived system.

Grounding is the intentional connection of a current carrying conductor to ground or something that serves the place of ground. In most instances, this connection is made at the supply source, such as a transformer, and at the main service disconnecting means of the premises utilizing the energy.

There are three basic reasons for grounding:

1. To limit the voltages caused by lightning or by accidental contact of the supply conductors with conductors of higher voltage.

2. To stabilize the voltage under normal operating conditions. This maintains the voltage at one level relative to ground, so that any equipment connected to the system will be subject only to that potential difference.

3. To facilitate the operation of overcurrent devices, such as fuses, circuit breakers, or relays, under ground fault conditions."



First off, I dislike the handbook, 2ndly, #3 in your post falls under equipment grounding, and not system grounding.
 

Alternety

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I believe that the grounds major practical purpose (not necessarily by code definition) is to prevent voltage from appearing on the enclosure of the power using equipment if there is an internal fault to the enclosure. The ground wire is connected to the neutral at one, and only one, point; the service entrance (and I think remote subpanels). I think it may be such a fault somewhere that was causing the hot bathtub. Thinking about the bathtub, if you are getting current between the water supply and the drain, I would think that there may be an issue of either a neutral touching a pipe or there being more than one earth ground tie in the system. One on the pipe and one on the drain (well we know that is true). The drain is a natural ground. The electrical system is bonded to the pipe. It would be interesting to know what the voltage in the tub is. If there is sufficient resistance between the purposeful ground and the intrinsic ground of the drain pipe there could be sufficient voltage developed for a nice wet body to feel a current flow in the tub. The resistance of your ground can vary from pretty much an insulator to almost a piece of wire. That is one reason that the ground is not really used to carry current in the distribution system. If you all wore a dry suit while showering the problem would be minimized.https://terrylove.com/forums/images/smilies/biggrin.gif

An example of differential ground currents - Many years ago, in a data center far far away, I took over a computer installation. When I would have equipment moved or install new equipment, sometimes the machines would run backwards. After that happened a couple of times I borrowed a scope from the computer service guy and looked at the power. The electricians, who threatened the IBM people with physical harm if they did any more power lines to the panels during initial construction, had no idea what three phase power was. Phase order was random on the connectors. The other thing they were told was not to have more than one earth ground point. They did not get that either. So they provided two. Now we are talking more power than the normal house consumes here, but the principle remains. In the course of fixing the mess (I shut the data center down for a day for rewiring) I picked up the power connector for one of the smaller computers. It was so hot I dropped it. There was a small voltage across the connector plug and socket connector shells. They are grounded. The plug was on one ground and the socket was on the other ground. Hundreds of amps were constantly flowing through the ground components of that circuit driven by the small voltage differential of the grounds.

In terms of lightening protection, the bolt is referenced to earth ground so the ground rod could make a difference. It is most useful when connected to surge suppressors where power, phone, and cable enter the house. At the voltage and amperage levels of a lightening strike the effects can get pretty strange. Think of your house as the other side of an air core transformer with a one turn primary coil passing thousands/millions of amps. A direct strike is not necessary to cause serious damage. I suspect that the plasma in a lightening bolt is in the range of plasma temperatures the physicists are trying to sustain in potential fusion generators.
 
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