Monday, September 04, 2006

Putting Your Life on the Line

Every day a maintenance technician, electrician, or even a homeowner puts their life into the hands of a voltage tester. Some are quick and easy to use while others have options that will never be explored. When you use a device to verify a de-energized circuit it is more important to make sure the verification is correct.

Lets look at a sampling of the testing unit variety available for our use. A lot of electricians have begun using a non-contact probe made by many manufacturers. These units are small, about the size of a pen, and easy to carry. The advantages of these units include the ability to detect the presence of electricity without touching the device. They can even sense the presence of electricity through insulation. But they depend on inductance and are only effective for testing alternating current circuits. These pens provide an indication of electricity and help diagnose circuit problems such as blown fuses. They are not the best option for verifying the ability to safely touch a possibly energized device.

Another small tester often used by many electricians is usually called by its nickname, a “Wiggy.” A more correct name for the device is a solenoid voltmeter. The unit uses power from the tested line to create a variable pull through an electrical solenoid which relates to the voltage sensed. Since the Wiggy directly contacts the circuit it is important to verify the Wiggy is properly rated for the circuit being tested. Are the device and test leads rated for the potential of the circuit? The Wiggy pulls a greater amount of current than most meters and can easily overheat if left connected to an electrical circuit. It too is a good indication of the presence of electricity but not a preferred method for personal safety testing of a possibly energized circuit.

The preferred method for testing an electrical circuit is the volt-ohm meter. It is supplied in varying designs by many manufacturers. Most of the volt-ohm meters measure the alternating current circuits using the root-mean squared value of the voltage. They can also measure and test direct current circuits as well. Generally a volt-ohm meter consumes very little power and provides little disturbance to the circuit being tested if power is present. As with the Wiggy, the user should verify that the meter being used for the test is properly rated for the circuit being tested. The most common meters are usually rated for no more than 600 volts and some of the better units are rated for 1000 volts. Many accidents happen when the user places the probes on medium voltage circuits such as 4,160 volt equipment which is much more power than the meter can withstand. Most often this mistake causes the meter to explode, severely injuring or killing the user.

Of course before using a volt-ohm meter you should make sure you are familiar with the operation of the meter and have read the user’s manual. Another test that helps insure the unit is providing correct indication is to test the meter on a circuit known to be energized. Of course this precaution is applicable to the non-contact and Wiggy meters too. Testing on a known circuit allows you to verify the meter and leads are in good working condition before you use them to verify a de-energized circuit where you will be putting yourself in harm’s way. This preliminary test is often skipped by many users and can easily lead to a fatal mistake.

As a final precaution you should make sure you are using proper personal protective equipment that would be necessary if the line were actually energized. Until the line is verified de-energized and properly grounded or locked out the user should always assume the line is energized. New regulations for arc flash and arc blast protection often frustrate the user when testing lines before verifying a de-energized circuit. But a few simple steps of precaution will allow you to remove the extra personal protective equipment and proceed with the job. Also never forget the possibility of other live circuits in the area where you are working. Examine the jobsite carefully and make sure you will be clear of these circuits or you will need to properly isolate those circuits as well.

Obviously we cannot cover all possible conditions in this brief thought provoking article. Hopefully this article will remind you to think the situation through before working on an electrical circuit. That moment of thought may save you from a severe electrical burn, shock, or death.