This post is just some thoughts on shocks, stray
voltage and rural homesteds.
A number of the posts sound like the problems are
actually related to the electricity supply to the whole farm. There are
quite a few WI dairy farms that have problems with cows going dry because of
shocks form the milking machine.
Everyone blames the milking machine, and then the
power company. The problems can go on for years. The basic thing is
that AC current from the power company does not have a ground wire. It
comes into the farm as three wires. Between two of them (supposed to be
colored black or red) a volt meter will measure 240 volts. The third wire
is white and is called the neutral. A volt meter will measure 120 volts to
either of the colored wires. If you want 240 V for say a water heater, you
connect the two colored wires. If you want 120 V for lights or a stock
tank heater you connect the white wire to either of the colored
wires.
For safety, the white wire is supposed to be
connected at the power pole (the bare wire that goes down the pole and into the
ground) to a rod going deep enough in the ground to contact enough wet earth
that the resistance between this wire, and a similar rod somewhere else on the
farm, is less than 25 ohms. The original idea was that if one of the hot
wires contacted a metal thing, that was in the wet ground, a fuse would blow and
noone would get a shock.
On many farms, the installation of some or all of
the ground rods are not good. They do not go deep enough, they are
corroded, a tractor broke the wire attached to them 20 years ago etc. Add
to this the fact that there are many barns wired with steel conduit or BX cable
still in operation. Over the years the ammonia fumes have corroded
the steel and what used to be solidly connected to a ground rod, now would
measure thousands of ohms resistance. This means that a safety ground
(green or bare wire) hooked to a tank heater can exhibit enough voltage to give
a shock EVEN IF THE HEATER IS PERFECT.
Fixing the problem is not hard, the hard part is
figuring out where the problem actually is. It is compounded by the human
reaction of power companies who find it much easier to blame their customer than
to spend lots of money tracing the fault. In the power companies defence,
most problems probably are not their fault, just some of them.
If I had a tank that seemed to be hot I would first
check the resistance between the round pin on the plug and the other pins, with
a good ohm meter. It should be several million ohms. If it is, then
you have to get help and start working to eliminate the problem Please
note: If you do not have a good volt ohm meter hire an electrician.
Touching things to see if the shock has gone away is not a safe way to find
electrical problems. . The problem can easily escalate from a mild
shock on the stock tank, to a fatal jolt from touching some other metal object
on or around the farm.
Ed
Ed & Wendy Hauser 2994 Mittower
Road Victor, MT 59875
