In order to avoid the harmful effects of possible electrical shock or electrocution, it is necessary for you or for the practicing electrician to be cautious and follow closely these safety practices:
Rule 1: Always consider safety first
Safety must be considered first when working with any type of electrical equipment or circuitry.
Rule 2: Wear Electrical Safety Precaution safety glasses
The majority of your wiring-laboratory exercises or job duties will involve either moving parts and machinery, or electrical devices that when wired incorrectly may come apart or even explode.
Rule 3: Remove all jewelry when working with energized electrical equipment.
- Metals used in rings, watches, or necklaces are good conductors! To compound the problem, moisture is normally trapped under rings and watchbands. Your skin resistance will be reduced drastically.
- The vinyl or other plastic watchbands that are popular these days appear safe since plastic functions as an insulator, but these too should be removed. Moisture will collect on the skin under this type of jewelry. The band could serve to entrap a live wire between the watch and your skin.
- Electricity is not a choosy phenomenon! Keeping all jewelry away from electrical circuits is of utmost importance to your safety.
Rule 4: Don’t place both hands on an energized circuit at the same time.
- This action could provide an additional path for current to flow through your body.
- When troubleshooting live circuits contained in power cabinets or other electrical equipment, the safe procedure is to work with one hand behind your back.
Rule 5: Remain insulated from any grounded source (surface).
- Almost all electrical circuits, whether high-power distribution circuits, lighting and receptacle circuits, motor drive circuits, or low-power control circuits, have one side of the circuit connected common to the electrical power distribution service equipment-grounding/grounding-electrode system. This configuration means these circuits are referenced to earth ground.
- If you are grounded, which is the rule versus the exception, you will provide a path for current to flow through your body by touching the electrical circuit at any point.
- The concrete you are standing on in the motor-controls wiring laboratory or at the worksite is also connected to earth ground through the same grounding-electrode system as the electrical-power distribution system. Rubber or other insulating-type shoe soles can never be depended on as adequate insulators. (Because sweat is salty. The, the moisture will penetrate this type of footwear, or even worse leather soles, to create a low-resistance path.)
- Exposed metal in a building or other structure is also connected (bonded) to the service grounding-electrode system. Rubber insulating mats (when available) should be used. This need is especially true for high-power/high-voltage circuits.
- When in the motor-controls wiring laboratory, notice that your lab stations are constructed of wood and the concrete floor is sealed with a coat of polyurethane that appears to be an insulator. But is it? Remember the position you put yourself in when you make assumptions. (How do you spell “assume”?)”?)
Rule 6: Ground all equipment enclosures including test equipment.
- Grounding is especially important, especially when high voltages are present.
- Bench equipment, such as oscilloscopes, volt-ohm meters, or power supplies in the wiring laboratory or repair shop are grounded by the third (green) wire in their power supply cord.
- Portable equipment, such as hand-held voltmeters, should not be grounded, simply because they are self-contained.
- Metal enclosures, such as junction, switch, or outlet boxes should be effectively grounded by a separate, green equipment-grounding conductor. This rule holds true for other enclosures, such as fused disconnects, pushbutton control stations, or motor housings.
- Metal raceways, which connect such enclosures, should be grounded with double locknuts: one on the inside and one on the outside of the enclosure. Metal conduits, which use compression fittings, should be grounded to the metal enclosure by the firm shoulder of the pipe-to-box adapter (box connector) on the outside and a single locknut on the inside.
Rule 7: Don’t activate electromechanical devices with a pencil or metal tool.
This safety rule applies to any type of electrical equipment or circuitry as well. Insulated circuit conductors should never be poked or prodded with a pencil or metal tool.
- Pencil lead is made of graphite: An excellent conductor. Don’t let this pencil become just an extension of your finger.
- Although a screwdriver normally has an insulated handle made of hard plastic, and most electrical screwdrivers have a rubber sheath on top of the hard plastic, the shank or shaft of the screwdriver is steel, which is also a very good conductor of electricity.
Rule 8: Always turn off or remove all power before making any alterations to the circuit wiring.
Effective troubleshooting normally involves taking voltage measurements at different key points (usually at various points of conductor termination) throughout an electrical circuit.
- If you are going to modify the wiring-laboratory exercise, or if you are going to remove components on the job for repair, turn off all power supplied to the circuit, cabinet, or equipment involved before you proceed!
- Normally, electrical panels or cabinets on the job are provided with a disconnecting means that is capable of being locked in the open position. Unless the disconnecting means is in your immediate vicinity and totally under your control (standard in all motor-controls wiring laboratories), a lock and your key is the best means of attaining electrical safety (LOTO ― Lock-Out Tag-Out).
Rule 9: No horseplay.
Fun is fun, but everything has its place. Kidding around with someone while they are working with live circuitry (whether in the laboratory or on the job) can have caustic or fatal consequences. The work you or your partner (It’s never a good idea for an electrician to work alone where live circuitry may be encountered!) is performing needs yours or their undivided attention.
Rule 10: Never work on live circuitry alone.
- Although each of you is required to perform your own wiring-laboratory exercise, you should not work in an electrical wiring laboratory by yourself. When you are working on live circuitry, another student, the designated lab technician, or the instructor should be in the immediate vicinity at all times.
- On the job, working on live circuitry (especially high-voltage) by yourself may be the last thing you ever do. The buddy system is the way to go. One of you should be watching and/or advising while the other is taking measurements with test equipment. If you should slip up and the painful sequence of electrical shock or electrocution begins; your buddy can attempt to rescue you. (Refer to Safety Rule 11).
Rule 11: Purpose/Use of the pole (cane) and the rope.
- Each wiring laboratory or job site should be equipped with a hooked-pole or walking cane and a piece of rope. This equipment should be used on anyone who has grabbed hold of a hot (live) wire and cannot let go.
1. The handle-end of the walking cane is normally hooked around the arm above the wrist. The arm and hand touching the live wire or other energized equipment is then drawn clear of electrical contact by pulling on the shaft of the cane.
2. If a person has slumped over the energized equipment, a length of the rope can be passed over the victim’s head to the chest (or back)). Then you grab both ends of the rope and leaning or pulling backwards, the victim can be drawn clear of electrical contact.
- Do not grab an individual who is in such a predicament with your bare hands, or you too may suffer electrocution. (You place yourself in parallel with the victim by grabbing hold of an arm or a leg, or the person’s trunk.) Pull or push (cane) the individual away from the hot wire by using the rope or cane.
Rule 12: Above all; follow instructions.
Make certain you know what you are doing before you proceed with either a wiring laboratory or installation or troubleshooting on the job. Seek additional help from your instructor, the designated lab technician, or your supervisor (on the job site) when in doubt about any safety procedure.
Whether installing, servicing, troubleshooting, repairing, or upgrading electrical circuits, treat all as if they are live (energized) circuits. Never assume someone else has turned off the power. Never assume someone else would not dare turn on the power (lockout disconnects).