PORTABLE ELECTRIC TOOL TESTERS If you have ever had an encounter with an ungrounded electric drill while working in the rain, you have a feel for the importance of tool testing. You will also have gained a healthy respect for the person who tests tools at the battalion central tool room (CTR) or the Public Works Department (PWD) when he or she fmds and corrects the problem with portable electric power tools.

The tool tester shown in figure 7-16 is an example of a tool tester that personnel from CTR or PWD might use.

The tool tester consists of a transformer, sensing relays, indicator lights, an audible warning buzzer, and leads suitable for tool or appliance connections.

Figure 7-16.- Typical tool tester. The transformer passes approximately 30 amperes through the tool cord equipment ground, burning away any "whiskers" that may be causing a poor equipment ground If there is no equipment ground, the OPEN EQUIPMENT GROUND sensing relay is activated, and appropriate warnings are given (the OPEN EQUIPMENT GROUND light glows).

If the resistance of the ground on the equipment under test is approximately 0.2 to 1.5 ohms, the FAULTY EQUIPMENT GROUND sensing relay is activated Resistance in excess of this amount activates the OPEN EQUIPMENT GROUND sensing relay.

The range in length of extension cords that can be tested is from approximately 6 feet to 100 feet of 16- gauge wire. These lengths will be longer or shorter in other gauges. The sensing circuit can be adjusted for different sensitivities.

The presence of a dangerous POWER GROUND, caused by carbon, moisture paths, or insulation breakdown, is checked at a 500-volt potential or at a 120-volt potential when the RF TEST button is pressed. The equipment, line cord, and switch are tested for SHORT CIRCUIT.

Faulty conditions are indicated by the corresponding light (red) and buzzer. One faulty condition must be corrected before another one will be indicated.

Tests proceed only when the equipment ground is in a safe condition. All tests (except the power ground) are conducted at potentials less than 10 volts.

If no electrical defects are found, the tool operates at its proper voltage to reveal any mechanical faults.

Optional features are installed to simplify two-wire and double-insulated tool tests and provide for safely testing double-insulated tools for power grounds.

WARNING The tool operates at the end of the test cycle. Be sure moving parts are faced away from the operator and have proper clearance to operate. Remove any removable cutting blade or bit before the tool is tested Do not come in physical contact with the tool during the test.

MAINTENANCE OF POWER TOOLS It is the task of a CE to ensure the proper operation of all power tools within his or her realm of responsibility. The program itself will be formulated by higher authority. The best way to perform this task is to develop a good inspection and maintenance program. Periodically, you should check all power tools for loose connections, pitted contacts, improper mounting of switches, and so forth.

The inspection and maintenance of power tools go hand in hand, and, in most cases, a problem discovered during inspection is corrected on the spot and requires no further work until the next inspection.

TEST EQUIPMENT Test equipment and experienced Construction Electricians are not always needed to locate problems.

Anyone who sees a ground wire dangling beneath a lightning arrester might suspect a problem. Little skill is required to consider an electrical service problem as a possible reason for the lack of power in a building.

Arcing, loud noises, and charred or burned electrical equipment sometimes indicate electrical faults; however, hidden, noiseless circuit problems are much more common and usually much harder to locate. The right test equipment and the Construction Electrician who knows how to use it are a valuable combination for solving electrical circuit problems.

No attempt will be made in this chapter to explain the internal workings of test equipment, such as meter movement or circuitry. Information on these subjects is covered in Navy Electricity and Electronics Training Series (NEETS) modules, published by the Naval Education and Training Program Management Support Activity. Test equipment is discussed in Modules 3 and 16. Your education services officer (ESO) should stock the NEETS modules. If not, he or she can order them for you. Other information on the use of test and circuit measuring equipment is included in modules throughout the NEETS series. This section introduces to you the types of test equipment used by the Construction Electrician in the field.

WARNING Naval Facilities Command (NAVFAC) requires that tests of electrical equipment be performed under the supervision of qualified electrical personnel. If in-house personnel are not available for these tests, the services of a qualified electrical testing contractor may be used. If you do not know how to do certain tests that must be performed, go to your seniors (crew leader and/ or project chief). Be certain that you can perform the test safely before starting the test procedure.