conduits (fig. 5-7). With cables having varnished- cambric insulation, it also may be necessary to clamp the conductor.
2. Junction boxes may be inserted in the conduit system at required intervals. Insulating supports of an approved type must be installed in the junction boxes and secured in a satisfactory manner to withstand the weight of the attached conductors. The boxes must be provided with proper covers.
3. The cables may be supported in junction boxes by deflecting them (fig. 5-8) not less than 90 degrees and carrying them horizontally to a distance not less than twice the diameter of the cable. The cables may be carried on two or more insulating supports and additionally secured by tie wires. When this method is used, the cables will be supported at intervals not greater than 20 percent of those mentioned in the preceding table.
In this section, you will find out how easy it is to assist and train your crew in troubleshooting. Many
Figure 5-7. - Gable support screwed on the end of a conduit and the one piece plug type.
different types of electrical multimeters are available to assist you. Electrical circuits can be tested safely and inexpensively with a neon tester (fig. 5-9). Most electrical problems can be solved just by determining the presence or absence of voltage.
One of the most common tests made with a neon tester is determining whether a receptacle is providing power. Figure 5-10 shows the first step in testing a receptacle. Each lead of the tester is firmly pressed into the receptacle slots to form a good electrical contact.
If voltage is present. the neon tester will glow softly for a 110-volt circuit and more brightly for a 220-volt circuit. If the tester does not light, the receptacle cover should be removed so that a second voltage check can be made at the terminals of the receptacle (fig. 5-11). If voltage is present at the terminals but not at the receptacle, the receptacle is defective and should be replaced. If voltage is not present at either the receptacle or its terminals, the problem lies in the overload protection or in the electrical circuit leading to the troubled receptacle. When the problem is in the electrical circuit leading to the receptacle, check each splice or each terminal point along the entire circuit for a break or a loose connection.
Determining whether a switch is defective requires only a simple two-step procedure. You must determine whether voltage is reaching the switch and whether voltage is passing through the switch.
Figure 5-12 shows how you can position the neon tester to determine if voltage is reaching the switch. Figure 5-13 shows how you reposition the tester to determine if voltage is going through.
With a grounded system, you need only touch the metal box and the terminals (figs. 5-12 and 5-13), or you may find it necessary to remove the wire nut from the neutral wire and use the neutral as the other test point. If voltage is not present at either switch terminal, the problem lies in the overload protection or in the electrical circuit leading to the troubled switch.Continue Reading