Choosing and using test equipment correctly is critical
There are no proven tricks or shortcutsthat will estimate the voltage in a circuit. Qualified workers must use a tester to determine if the wires or equipment are energized. All too often, electricians are injured or killed while performing tests due to equipment failure or human error. Although test instruments usually have thermistors, varistors and fuses that limit or prevent damage from internal short circuits, they do not protect from shock or arc flash. The protective device won’t clear the circuit in time. And, if a test fails without resulting in a shock or flash, it means the electrician is not aware of the existence or level of energy in the line. As a result, the electrician begins work on the circuit thinking it’s safe and may be injured or killed.
Typically, accidents associated with testing occur when companies do not have written policies and procedures in place. A program should be developed that addresses the selection, purchase, maintenance and use of test instruments. The program must take into account possible equipment deficiencies and human error.
In the absence of a program, accidents will occur. Although the immediate cause of the accident will be identified (equipment failure or human error), the underlying cause, such as using the wrong tester for the job, might be missed. It is imperative that basic guidelines be established and followed.
Before using a tester or meter, be sure of the following:
- Your company has established specifications for testers. Make sure equipment meets the conditions that will be faced in the field. Limiting the number of suppliers and models will simplify training.
- Provide training. Make sure employees know how to use the tester. Have them read and follow all manufacturer’s instructions. Seek the assistance of someone who has used the tester before. Manufacturers often provide schools to train users. Training should cover the hazards and limitations of each instrument you plan to use.
- Limit the use of multimeters. Analog and digital multimeters have manual settings. A common problem is that employees switch to an ohmmeter or ammeter setting, instead of voltage, and then connect to a voltage source. To avoid this human error, consider using single-function voltmeters or other instruments that don’t depend on manual settings. Also, avoid meters that have manual test lead plug connections. Limiting manual options reduces the opportunity for operator error.
- Where possible, know the voltage levels that may be carried by the wires or equipment that you will be testing. Do not depend on electrical diagrams. When working with equipment, follow the wires back to the source and look for the voltage.
- Select the appropriate tester or setting. Testers are designed for a specific voltage range. The tester or setting should match the voltage of the equipment or lines you will be working on or near. When you are unsure, always select for the maximum voltage. Start with the highest setting or instrument and reduce one step at a time until a reading is achieved.
- Do not exceed an instrument’s limitations. Many solenoid-plunger-type testers have a thermal duty cycle limit. If you exceed these limits, the solenoid coil could fail. This instrument cannot be used for continuous service.
- Retire obsolete instruments. Review your inventory to identify these instruments. Many instruments often found in the field predate recognized safety standards needed to prevent accidents.
- Know the equipment you are testing. Stored energy sources, such as capacitors, and the possibility of back feed should be tested. Knowing the equipment will enable you to test properly for all hazards. Read all manufacturers’ instructions and contact the manufacturer for more information.
- Always wear the proper protective equipment when testing or working near energized parts. The National Fire Protection Association (NFPA) Standard 70E stipulates what equipment is necessary based on the hazard level. It should be used as a reference. A quick guide, the NFPA 70E Personal Protective Equipment (PPE) Selector, to the standard and equipment needed is available from the National Electrical Contractors Association in an interactive CD format and a printed field guide.
Finally, make sure you monitor your program. Audit, test and inspect. Audit policies, procedures and employee qualifications. Are procedures and employee training up-to-date with current standards and equipment used?
Check the testers. Have the testers been calibrated and tested in accordance with the manufacturer’s specifications? Inspect the equipment and employee use of equipment in the field. Is the equipment in top condition? Do employees use the equipment as it is intended to be used? Making sure all is in order on a regular basis will save lives. EC
O’CONNOR is with Intec, a safety consulting, training and publishing firm that offers on-site assistance and produces manuals, training videos and software for contractors. Based in Waverly, Pa., he can be reached at 607.624.7159 or by e-mail at firstname.lastname@example.org.