2003-01-25 In addition, a copper wire is run from the fuse box neutral post to the water pipe inside the house. At least here in Cleveland it is. Some years ago, the neighbour next door experienced the very thing you spoke of. The neighbour lady called me over to have me check to see why her appliances and lights were acting funny. I discovered the line was not balanced. The voltage from one side to neutral was low and the other side to neutral was high.
I pulled the main fuse out to prevent damage to her appliances. I discovered that the ground wire connecting the neutral tap of the fuse box to the water pipe was missing. I had some 10 ga wire and a spare water pipe ground terminal at home. I connected the wire from the cold water pipe to the neutral tap. I plugged the fuses back in and checked the voltages and the balance had been restored. I was surprised the ground wire had been missing, but there was nothing that could have been done since it was that way for over 30 years. I told her to call the power company to see why the neutral was lost from the pole to the house. It turned out that the incoming neutral line had broke. In our neighbourhood, the neutral line is not insulated and the two insulated hot lines are wrapped around the neutral line (braided). Somehow, from who knows what, the wire just broke. The power company just spliced the neutral line back together. And everything was fine again. But, this made me think. With the ground wire missing from the water pipe to the neutral bar, she knew right away there was a problem. If the wire had been there, she may have never known that her neutral line was open coming from the pole. Relying on the water pipe to balance the load may cause a situation you mentioned with the cows. If the voltage drop from the water pipe to the transformer centre tap was a few volts above true ground, someone could possibly experience a shock when they touched the water pipe near the point where the ground tap is mounted. I wonder which is better to be grounded to the water pipe or not. Sounds like a no win situation. John > An earth ground is established at the output (the winding's center tap) > of the transformer supplying the secondary crib and also at each house > receiving service. An extremely hazardous but fortunately rare occurance > can arise, called a "floating neutral". If the connection to earth is > lost, the house's "ground bus" actually floats between the two hot > phases. If one phase is more heavily loaded than the other phase, the > voltage on the heavily loaded phase drops while the voltage on the > lightly loaded phase rises. I have observed this twice, once in > Connecticut and once in South Carolina. In each case, I could typically > measure 70 V on one side and 165 V on the other! The two voltages I > mention observing still total to 235 V, but they differ because the > neutral has floated away from ground potential. When this happens, one's > attention is called to the matter because some of the lights in the > house shine more brilliantly than ever and others glow very dimly. Or, > the starting of a large load causes even more momentary dimming than > normal in the lights on that load's phase while the lights on the other > phase brighten momentarily. If it is not noticed, it can eventually lead > to damage of appliances or even a house fire. > > Because the ground (earth) connections at homes may or may not be very > effective (they get worse in times of drought), power companies often > run a neutral wire to each house to ensure that the secondary > transformer ground potential is the same as the house ground potential. > This practice was first started when automatic milking machines came > into wide use. Some farmers complained that their cows would not give > milk at times when the machines were used and sometimes the cows even > shied away from them. The "power" companies investigated and found that > there could typically be a quarter volt difference (sometimes as much as > a volt) in potential between the ground rod at the barn and the one at > the pole on which the secondary transformer was mounted. In effect, a > ground loop current was created in which the cows' teats were part of > the circuit. No wonder the cows shied away! > > Jim > > -- > James R. Frysinger > Lifetime Certified Advanced Metrication Specialist > Senior Member, IEEE > > http://www.cofc.edu/~frysingj > [EMAIL PROTECTED] > [EMAIL PROTECTED] > > Office: > Physics Lab Manager, Lecturer > Dept. of Physics and Astronomy > University/College of Charleston > 66 George Street > Charleston, SC 29424 > 843.953.7644 (phone) > 843.953.4824 (FAX) > > Home: > 10 Captiva Row > Charleston, SC 29407 > 843.225.0805 >
