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Electrical Safety Considerations
Before reading
this topic, you must first understand the basic
electricity-1 topic for best results. This topic will point
out some safety concerns that you need to be aware of. Take some
time and read this topic, it is VERY IMPORTANT. This topic can
not possibly address all safety precautions, and is not intended
to be all inclusive. These are just some of the representative
safety issues.
Hot
Truck Chassis & Death
The 12 volt
battery circuits on a truck will not kill you, so touching active
(hot) truck circuits isn't dangerous. A hot truck chassis, on
the other hand, can kill you. When we talk about a hot truck chassis
here, we are referring to 110Vac house current coming into contact
with the truck chassis. For example, you could be using an old
drop light, and a frayed part of the cord transfers 110Vac to
the entire truck chassis. Will the 110Vac circuit breaker trip
because of the chassis contact? Probably not, since the truck
is sitting on rubber tires, and rubber is a good insulator.
Most garage
floors are damp concrete, which makes for a good conductor and
ground path. If you stand on the damp concrete and touch the hot
truck chassis, your body becomes the 110Vac load resistance, which
could result in a lethal shock. If it isn't lethal, it will hurt
a lot, and could cause you to be nervous and jittery for quite
a long time afterward. You should always seek medical attention
after a serious shock, because you heart beat could become erratic
or stop completely without warning.
The best
way to prevent this situation, is to attach a heavy grounding
strap to the truck chassis. With the grounding strap attached,
the above frayed cord situation would result in tripping the 110Vac
circuit breaker. It is much better to have the grounding strap
trip the circuit breaker, instead of your body. In fact, your
body would not trip the breaker even while you are being shocked
to death. It only takes about 1/100 amps passing through your
heart to kill you. That drop light circuit breaker is probably
rated at 15 amps. Therefore, the circuit breaker could supply
1500 times the amount of current that is required to kill you.
Fortunately,
not all is gloom and doom here. Your leather or rubber shoes offer
some degree of resistance between you and that damp concrete.
To maximize the current flow through your heart, current must
flow from one arm to the other arm, or from your left arm to either
leg. Due to the insulating quality of your shoes, you most likely
will not die when touching a hot chassis, but don't count on it.
If your feet are wet or sweaty, then the insulating property of
your shoes is seriously compromised.
Remember
one thing, if you are touching the hot truck chassis with one
hand (insulated shoes are protecting you) and then you grab a
metal cased electric power tool with the other hand (most electrical
power tools have the case grounded for safety), the safety feature
of the power tool may have just killed you. You have now placed
110Vac between both hands, and your heart now gets maximum and
possibly lethal current flow.
There is
one other hot chassis situation caused by mother nature. If you
are touching a truck chassis when lightning strikes that vehicle,
you become the lightning rod. You provide the path to ground for
the lightning strike. Your rubber shoes will provide little protection
since the high voltage of the lightning strike will jump right
across your rubber shoes and fry you in the process. It is not
a good idea to be crawling into and out of your truck while lightning
strikes are a threat.
Eliminate
Accidental Shorts and Burns
The main
battery cables run directly to the starter motor, with no fuses
involved. Therefore, before working on the starter, you must disconnect
one of the battery cables first. Any electrical repairs which
involve unfused circuits, requires that the battery be disconnected.
If the electrical part to be serviced has a fuse or circuit breaker,
remove the fuse or circuit breaker before servicing that part.
If a wrench
contacts the unfused circuit and ground at the same time, then
sparks will fly and the wrench will get very hot very quickly.
This can result in burned insulation of the associated wires due
to the excessive heat generated by the short circuit current.
It can also result in burns to your hand if you don't let go of
the wrench before it gets hot. The arcing action can also damage
surrounding surfaces or parts, and sometimes the wrench actually
spot welds in place.
Always disconnect
the battery before servicing unfused circuits. Always!
Gold
Jewelry Dangers
Another
danger while working around electrical parts, is the wearing of
gold jewelry. As you may know, gold is one of the most perfect
conductors. Imagine what happens if your gold ring completes the
path from the hot side of the battery to ground. The gold ring
passes massive current, heats up red hot in a second, and begins
burning its way through your ring finger. And guess what? You
can't just grab it and pull it off, because it will burn the fingers
that you grab it with!
The
same thing could happen to other gold items of jewelry. A gold
wrist bracelet dangling near an unfused battery circuit can do
the same thing to your wrist that the ring can do to your finger.
Jewelry and electrical repairs do not mix.
Cuts
From Broken Light Bulbs
Have
you ever broken a bulb trying to get it out of its socket? Usually,
the glass separates from the brass base of the bulb, but sometimes
the bulb will crush, resulting in cut fingers. Don't use your
unprotected fingers to remove stubborn light bulbs.
Battery
Dangers
Batteries
present several different forms of danger. First, they are very
heavy and can cause wrenching of the back if you are not careful.
They also contain acid, which can cause eye injury if splashed
into the eyes. The battery acid will also eat holes in your clothes.
The battery is also the source of power for the burn situations
discussed above. Any conductor which shorts between the two battery
posts, could become a flesh burning branding iron.
Batteries
can also become bombs. Let me say that again, batteries can also
become bombs. In basic electricity, we explained that batteries
generate hydrogen gas while being charged. If a battery is being
fast charged, then this explosive gas is generated in large volume.
All it takes is for a spark to occur near the battery vents, and
presto, all of that hydrogen gas inside the battery explodes.
Lets
take a typical explosive situation. The truck battery is dead,
so you place it on fast charge. A half-hour later you try to start
the truck, but there is a loose battery connection at the battery
post. You now have hydrogen gas venting from the fast change,
and a spark from the loose battery connection which is right next
to the battery vents. Never stand near any battery while cranking
the engine.
When
the battery explodes, it expels several projectiles. First it
splinters the battery case and all those splinters become projectiles
which can penetrate your body and eyes. Right behind the case
pieces comes the acid which is also not good for your eyes. And
right behind the acid comes the lead plate pieces. Lead poisoning
is a real threat, so imagine a large number of lead particles
soaked in battery acid and embedded throughout your body and eyes.
Another
situation where batteries can explode is during jump starts. If
you put the jumper cables on backwards, positive to negative
and negative to positive, you now have a battery war on your
hands. The two batteries are fighting which results in excessive
currents, hydrogen gassing, and sparks when you remove the reversed
jumper cables. This has all the ingredients for a battery explosion.
There
are other situations for battery explosions, including fast charging
of frozen batteries. Just remember, batteries are energy storage
devices. Make sure that you do not release this energy in unexpected
ways.
Burns
From Hot Motors and Light Bulbs
Electrical
things get hot under normal conditions. This heat is a result
of resistance losses inside the device. For example, a truck starter
motor gets very hot if you crank the engine for a long time. If
you reach out and touch that motor right after extensive cranking,
you may leave a layer of your skin on that motor, or you may have
finger blisters before you know what happened.
When
there is a problem, the current can be excessive, and the resultant
heat can be much greater than normal. The electrical device can
get overheated, and the wires connecting to the device can also
get very hot.
Light
bulbs can also get very hot while in use. So don't just reach
in and try to remove a lighted light bulb without some hand protection.
This
topic in no way covers every electrical safety consideration that
you should make. Your own common sense must also come into play
for adequate safety protection for situations not covered in this
topic.
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