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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.Just FYI, you should really use an amprobe before you disconnect water mains and such, it could save your life.
It killed him.
Originally Posted by Terry
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.
What size amprobe would be big enuff to clamp around the water main to measure the current??
I had that happen to me
I lost one of my 9 lives a long time ago this way...
the only thing that saved me from being lit up was the
inslulated channel locks I was useing while kneeling in a pool of water working on the main at the water meter
in someones basement ...
when I cut the line all the lights in the house went out....
and it scarred the channel locks...
I jumped backwards very quickly...
Several years ago I worked with a plumber and we did primarily restaurant renovations.
The one thing I can remember that Jack always did when opening the metal pipes of one of these old buildings was use a jumper cable across the place he was opening. Yes the same kind of cables used to boost a car.
It wouldn’t matter where the pipe was to be opened or if power was on to the building or not the cable was used.
Jack was a very smart man!
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.
Terry, do you have a link to this article, or other info that i could read on this??
It was Mark Tullis, City of Bellevue plumbing inspector who told me on the incident. Mark Tullis 425-452-4566Terry, do you have a link to this article, or other info that i could read on this??
FYI - I searched google.com for the words...
plumber electrocuted
...and it seems this has happened quite a bit.
That is not what it says in my 1996 NEC handbook!
So lets hear it... I didnt type it verbatim if thats what your saying.
Why are you still using a 1996 book?
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.
Last edited by hj; 09-05-2008 at 01:16 PM.
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.
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.
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