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Unformatted text preview: 35-40 gallons of water, then plugged a mixing motor into a 120-volt wall outlet and turned on the motor. The motor would be used to mix the water and the chemical, then the solution would be added to the pool. While adding the chemical to the water in the drum, she contacted the mixing motor with her left hand. Apparently, the motor had developed a ground fault. Because of the ground fault, the motor was energized, and she was electrocuted. A coworker found the victim slumped over the drum with her face submerged in water. The co-worker tried to move the victim but was shocked. The assistant manager was dead on arrival at a local hospital. An investigation showed that the mixing motor was in poor condition. The grounding pin had been removed from the male end of the power cord, resulting in a faulty ground. The circuit was equipped with a GFCI, but it was not installed properly. A properly wired and functioning GFCI could have sensed the ground fault in the motor and de-energized the circuit. Take a look at what could have been done to prevent this death. The employer should have kept the motor in better condition. Power cords should be inspected regularly, and any missing ground prongs should be replaced. All pool-area electrical circuits should be installed by qualified electricians. The victim should have worn insulating boots or shoes since she was handling electrical equipment. The employer should have followed the law. The NEC requires that all pool-associated motors have a permanent grounding system. In this case, this regulation was not followed. Also, electrical equipment is not permitted in areas without proper drainage. OSHA requires employers to provide a work environment free of safety and health hazards. The NEC and NFPA 70E require that GFCIs be used in these highrisk situations: Electricity is used near water. The user of electrical equipment is grounded (by touching grounded material). Circuits are providing power to portable tools or outdoor receptacles. Temporary wiring or extension cords are used. Specifically, GFCIs must be installed in bathrooms, garages, outdoor areas, crawl spaces, unfinished basements, kitchens, and near wet bars. Bond components to assure grounding path In order to assure a continuous, reliable electrical path to ground, a bonding jumper wire is used to make sure electrical parts are connected. Some physical connections, like metal conduit coming into a bonding--joining electrical parts to assure a conductive path Install bonding jumpers around nonconductive material. Use GFCIs to help protect people in damp areas. Section 7 Page 51 S AF ET Y M O D EL S TAG E 3--C O N T rOLLING HAZArDS: SAFE WOrK ENVIrON M EN T bonding jumper--the conductor used to connect parts to be bonded box, might not make a good electrical connection because of paint or possible corrosion. To make a good electrical connection, a bonding jumper needs to be installed. A metal cold water pipe that is part of a path to ground may need bonding jumpers around plastic antivibration devices, plastic water meters, or sections of plastic pipe. A bonding jumper is made of conductive material and is tightly connected to metal pipes with screws or clamps to bypass the plastic and assure a continuous grounding path. Bonding jumpers are necessary because plastic does not conduct electricity and would interrupt the path to ground. Additionally, interior metal plumbing must be bonded to the ground for electrical service equipment in order to keep all grounds at the same potential (0 volts). Even metal air ducts should be bonded to electrical service equipment. Control overload current hazards
When a current exceeds the current rating of equipment or wiring, a hazard exists. The wiring in the circuit, equipment, or tool cannot handle the current without heating up or even melting. Not only will the wiring or tool be damaged, but the high temperature of the conductor can also cause a fire. To prevent this from happening, an overcurrent protection device (circuit breaker or fuse) is used in a circuit. These devices open a circuit automatically if they detect current in excess of the current rating of equipment or wiring. This excess current can be caused by an overload, short circuit, or highlevel ground fault. Use overcurrent protection devices (circuit breakers or fuses) in circuits. Page 52 Section 7 Overcurrent protection devices are designed to protect equipment and structures from fire. They do not protect you from electrical shock! Overcurrent protection devices stop the flow of current in a circuit when the amperage is too high for the circuit. A circuit breaker or fuse will not stop the relatively small amount of current that can cause injury or death. Death can result from 20 mA (.020 amps) through the chest (see Section 2). A typical residential circuit breaker or fuse will not shut off the circuit until a current of more than 20 amps is reached! But overcurrent protection devices are not allowed in areas where they could be exposed to physical damage or in hazar...
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- Spring '09