Electricity is the invisible force that powers our homes and drives the tools that we use to repair and upgrade it. Electricity is also one of the most misunderstood energy sources encountered by the do-it-yourselfer. Most people fear it because they canÃÂt see it with the unaided eye and people naturally fear the unknown. It can jump out and bite you when you least expect it and the bite can be fatal but it can also be controlled. Like with most fears you can overcome them through knowledge. You can transform the fear into respect and once you do that you can work with and around electricity in a safe and secure manner. This is knowledge that every do-it-yourselfer needs to gain because electricity can hurt you even if the project that you are working on doesnÃÂt directly involve electricity.
According to the United States Consumer Safety Report published in 1995 based on statistics provided by NCHS (National Center for Health Safety) on electrocutions by consumer products, the home is truly a dangerous place for the unaware. According to the 1995 statistics, the latest statistics available, there were 550 electrocutions in and around the home because of consumer products. Out of a total of 560 electrocutions in the United States, 230 electrocutions or 41 percent were related to consumer products.
ÃÂ· Installed household wiring accounted for 23 percent, or 53 deaths caused by household electrocutions. You need to know whatÃÂs inside that wall youÃÂre cutting into with your Saws All.
ÃÂ· Another 17 percent, or 40 deaths, resulted from defective or improperly used small appliances.
ÃÂ· Another 14 percent, or 33 deaths, resulted from defective or improperly installed major appliances
ÃÂ· Another 10 percent, or 24 deaths, resulted from improperly installed television antennas.
ÃÂ· Another 9 percent, or 20 deaths, result from defective or improperly installed or used lighting equipment
ÃÂ· Another 7 percent, or 15 deaths resulted from people coming into contact with electrical wires while working on ladders
ÃÂ· Another 6 percent, or 13 deaths, resulted from using defective or improperly wired power tolls
ÃÂ· Another 6 percent, or 14 deaths resulted from defective or improperly used farm and garden equipment
ÃÂ· The remaining 8 percent or 18 deaths resulted miscellaneous causes of electrocution.
With those statistics in mind letÃÂs take a look at how electricity kills so you wonÃÂt become one of those statistics.
A common misunderstanding about electricity and electrocution.
Most people believe that itÃÂs the amount of voltage present that makes electricity dangerous or innocuous. ThatÃÂs the most common misconception. In reality, itÃÂs the amount of current flowing through your body that electrocutes you or send you to the hospital with grave injuries. Granted that there is a direct relationship between the amount of voltage present and the amount of current that can flow through a circuit no matter whether that circuit is completed by your body or an electrical conductor it takes very little voltage to force a fatal current to flow across your heart. People have been killed by voltages that most people would consider harmless, like the 24 V (Volts) present in a residential door chime circuit. Actually a current of 1A (Ampere) or less can shock the human heart into a state of arrhythmia. ThatÃÂs why GFCI (Ground Fault Current Interruption) devices which are designed to protect human beings against fatal electrical shocks are designed to trip out at 6mA (Milliamperes), 0.006A, or less.
Introduction to the OhmÃÂs Law
The OhmÃÂs Law states that the current is directly proportional to the voltage and inversely proportional to the resistance. The OhmÃÂs Law is represented by the formula I=E/R, where
ÃÂ· I = the current in Amperes
ÃÂ· E = the voltage in volts and
ÃÂ· R = the resistance in ? (Ohms)
In other words the current flowing through a circuit or through your body will increase as the voltage increases as long as the resistance presented to the flow of current remains constant.
Human physiology and electricity.
The human body contains 65 percent water by weight and water is a relatively good conductor of electricity. The internal body fluids have a resistance that varies between 300 to 1,000?. The body outer layer of skin, the epidermis, has a resistance that varies from 1,000 to 100,000? depending on its moisture content. If youÃÂre sweating profusely, the resistance of the epidermis can drop to 1,000? in an instant. The total resistance offered by the human body is represented by this formula
R (total) = R (skin in) + R (internal) + R (skin out)
This is one of the few areas where males truly are superior to females because a current of 9A is always fatal for a female where it takes an additional amp or 10A to always be fatal to a male. That brings us to the next question, how do those current relate to electrical potential or voltage. LetÃÂs calculate that voltage for a day when the wsweat is pouring off you like the water cascading over Niagara Falls.
R (total) = R (skin in) + R (internal) + R (skin out)
= 1,000? + 1,000? + 1,000?
E = I X R = 10A X 3,000?
= 30,000 V
Very few of us will ever encounter that kind of voltage unless we start tinkering with out color television sets or computer monitors. Homes in the United States are wired for 240/120 Volts, so why does that kill people? Even with the body operating at minimum resistance, 240 Volts can only produce a current of 0.08A which is 0.8 percent of what we stated above as always being fatal.
Household voltages can kill because it disrupts the hearts internal pacemaker driving the heart into a state of fibrillation.
ÃÂ· Fibrillation is the fine, rapid, erratic, movements that replace the normal contraction of the ventricular muscle of the heart
ÃÂ· Fibrillation can be stopped by application of another controlled electrical shock, known as defibrillation, often seen in movies and on TV...
ÃÂ· A stopped heart can often be resuscitated with CPR techniques (cardiopulmonary resuscitation), but seldom a fibrillating heart.
The following list shows you how various amounts of current affect the human body when the current flows across the chest and through the heart.
ÃÂ· <0.01 A causes a tingling sensation or isnÃÂt perceptible at all (< means less than)
ÃÂ· =0.02 A causes contraction of the muscles and you canÃÂt let go
ÃÂ· =0.03 A disturbance to respiration or breathing
ÃÂ· =0.07 A extremely hard to breathe
ÃÂ· =0.10 A fibrillation caused death
ÃÂ· >0.20 A fibrillation doesnÃÂt occur but severe burning occurs with paralysis of the respiratory system (> means greater than)
1. Treat every circuit that you are working on as if it were hot. This may slow you down but it will make safe working habits automatic and you wonÃÂt slip up when you have to work on an energized circuit.
2. When testing energized circuits work the way professional electricians do with one hand in their pocket. This way of working prevents you from providing a direct path across your chest and through your heart if your other hand accidentally comes into contact with live parts. If youÃÂre using a meter learn to use an alligator clip on one of the test leads.
3. If you canÃÂt lock a service panel door tape over the breaker and place a large sign on the panel advising other members of the household to not turn the circuit back on.
4. Where rubber sole shoes or boots
5. If you are working in a damp area stand on a rubber mat. If there is a lot of water on the floor, place the rubber mat on a wooden pallet to keep it from getting wet.
6. Watch out for overhead wires when working on a ladder.
7. Have the utility company come and mark the location of their underground lines before digging up the yard.
I always try to cover any special safety precautions to be taken with every tutorial that I publish but these will get you started off on the right foot.