conduits (fig. 5-7). With cables having varnished-
cambric insulation, it also may be necessary to clamp
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
TESTING ELECTRICAL CIRCUITS
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.
CHECKING FOR A DEFECTIVE
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
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
CHECKING FOR A DEFECTIVE
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.