- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURAL MECHANICS (CLF2650) Unit Title: ELECTRICITY ___________________________________________________________________________ (CLF2652) Topic: Electrical Safety Time Year(s) 1 hour 1 / 2 / 3 / 4 ___________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the students will be able to: Learning Outcome #: (N-1) - Use approved safety measures in electrical wiring. (N-7) - Exhibit safe habits when working around electricity. Special Material and Equipment: References: Cooper, E. L. (1987). AGRICULTURAL MECHANICS: FUNDAMENTALS AND APPLICATIONS. Albany, NY: Delmar Publishers. Gustafson, R. J. (1980). FUNDAMENTALS OF ELECTRICITY FOR AGRICULTURE.. Westport, CT: AVI Publishing Company. Phipps, Lloyd J., & Reynolds, Carl L. (1990). MECHANICS IN AGRICULTURE (4th ed.). Danville, IL: Interstate Publishers. Evaluation: Quiz by instructor. TOPIC PRESENTATION: Electrical Safety A. Electrical Hazards 1. Shock and fire are hazards associated with electric current. a. Shock refers to the body's reaction to the passing of electrical current through it. 1) Shock occurs from a fall in blood pressure resulting in a decrease of blood supply, and therefore oxygen, to the brain. 2) The increasing levels of electrical shock caused by increasing amperage makes it clear that voltage is not the killer, rather amperage is. 3) Shock hazard from electrical current is expressed in milliamperes. One millampere (commonly called a "milliamp") is equal to one thousandth of an ampere, i.e., A/1000 where A is the electrical current in amperes. The following gives an indication of the physical effects of current flow through the human body: a) barely perceptible - 2 milliamperes b) uncomfortable - 5 milliamperes c) muscular freeze - 10 milliamperes d) fatal - 15 milliamperes b. Fire may occur when electrical conductors overheat or when a spark is produced when an electric current jumps an air gap between conductors. 2. Terminology Associated with Electrical Hazards a. A short is a direct connection between a hot wire and a ground connection, allowing amperage to flow up to the limits of a fuse or wire. b. A fault is a leakage of current (a high resistance connection) from a hot wire to a ground connection, which may be of such low amperage that the circuit protection will not trip. c. A Ground Fault Circuit Interruption (G.F.C.I.) is a device that measures fault current and automatically opens the circuit at a preset value, usually 5-7 milliamperes. The purpose is to protect people from fatal shock. B. The Protection of People and Property 1. General Safety Rules a. Follow the manufacturer's instructions for installation and use of all electrical equipment. b. Never disconnect or damage a electrical safety device that is provided by the manufacturer. c. Do not touch electrical appliances, boxes, or wiring with wet hands. d. Do not remove the long ground prong from three-prong 120-volt plugs. e. Discontinue using any extension cord that feels warm or smells like burning rubber. f. Do not use any switches, outlets, fixtures, or extension cords that are cracked or damaged in any way. g. Do not place extension cords under carpeting. h. If a fuse is blown or a breaker is tripped, find and correct the problem before installing a new fuse or resetting the breaker. i. Do not leave heat-producing appliances such as irons, hair dryers, and soldering irons unattended. j. Keep metal cases of electrical appliances grounded. k. Keep electrical motors lubricated and free of grease and dirt. l. If attempting to rescue a person being electrocuted, touch him only after the circuit has been opened, or use an insulated object to move him off the hot wire. 2. Safety Measures in Electrical Wiring a. Install all electrical wiring according to the National Electrical Code. b. Open the circuit before touching any point on the circuit. c. Do not touch bare wires with hands or tools while the circuit is closed. d. Do not touch wires together to see if they are hot. e. Do not touch switches or fixtures with wet hands or while standing on wet ground. f. Do not connect a new circuit to the breaker box until all the wiring is completed. g. Do not install fuses or breakers with an amperage larger than recommended, or they will not protect the circuit from overheating. h. Do not overload a circuit with too many fixtures and outlets. i. Use only double insulated portable tools or tools with three-prong plugs. j. Insulate splices with electricians' tape or solderless connectors. k. Install ground fault interrupters in kitchens, bathrooms,laundry, and outdoor circuits, or wherever moisture may increase shock hazard. l. Use proper color coding of wires when installing a new circuit. 3. Product Safety Testing a. Underwriters Laboratories (U.L.) test sample products, such as electrical appliances and tools, to see if they safely do the job for which they were designed. b. U. L. lists those products tested indicating that they have performed safely. It is not an endorsement or statement of quality. c. The manufacturers of these listed products display a U. L. label indicating that they have been tested. SAFETY IN ELECTRICAL WORK* Observe the following general safety practices in doing all electrical work. 1. Avoid damp working areas. Never handle electrical equipment with wet hands or while standing in a wet or damp place. 2. Protect each circuit. Be certain that each circuit is protected with either a circuit breaker or a fuse of proper amperage. 3. Ground each circuit properly. Each circuit must have a ground (neutral) wire and a grounding wire to be properly grounded. 4. Use ground-fault circuit interrupters (GFCI's). To protect the operator who works outside or in damp locations, make sure the electrical source is protected by a ground-fault circuit interrupter. 5. Ground electrical equipment. All 120-volt electrical equipment should be equipped with a three-prong grounding-type plug or be double insulated. Never cut off a grounding prong just to make the connection work. 6. Disconnect the main switch. Before making any repairs on an electrical circuit, always make certain the current has been disconnected. 7. Correct the source of trouble. Before resetting circuit breakers or replacing blown fuses, correct the cause of the trouble. Repair or replace any equipment that gives a shock when it is used. 8. Purchase safe equipment. Select portable electrical equipment that is grounded with a three-prong plug or is double insulated. Look for the "UL" label, indicating that the equipment has been tested and approved by Underwriters Laboratories, Inc. 9. Review local electrical codes. When rewiring a building, follow the local electrical code. 10. Seek professional aid. Instead of using trial-and-error methods when electrical devices do not function properly, get professional help. 11. Avoid plumbing hazards. Do not locate switches or light fixtures near plumbing fixtures. 12. Inspect and repair cords periodically. Inspect all extension cords and electrical appliance cords periodically for exposed wires, faulty plugs, poor insulation, and loose connections. Correct all hazards found on electrical cords. 13. Open circuits with switches. Never pull a plug from an outlet while the equipment is in operation. This creates an arc and will eventually foul the plug or the outlet, which can cause electrical shock or a possible fire. 14. Never make temporary repairs. Make sure all repairs are as good as new. When splicing wires, be sure all strands are are twisted together, the connections are strong, and the splice is fully insulated. 15. Use electrical cords safely. Do not hang electrical cords on nails or run them under rugs or around pipes. Avoid using extension cords as permanent wiring installations. 16. Do not overload circuits. When new equipment is installed, make sure it is protected by a circuit of proper amperage rating. 17. Unplug electrical tools. Do not leave a tool plugged in when it is not in use, unless it is designed for continuous operation. _____________________ * Reprinted by permission of Interstate Publishers, Inc., from MODERN AGRICULTURAL MECHANICS, 2nd ed., by Stanley R. Burke and T. J. Wakeman. Copyright 1992 by Interstate Publishers, Inc. _________________________________________________________ ACTIVITY: 1. Pass written safety tests on electricity and keep them on file. 2. Observe a demonstration of first aid for electrical shock given by the local fire department. 3. Have each student complete a safety checklist of his or her own home's electrical system. The local fire department can provide a good checklist. _________________________________________________________ 6/26/91 OLR/tf #%&C