Figure 7-15.Single-pole oven timer wiring schematic.
APPLIANCE AND EQUIPMENT
MAINTENANCE, REPAIRS, AND
One of the primary responsibilities of a CE is to
ensure proper operation of switches and elements used
in appliances and equipment. That can be done by
developing and following a good inspection and
maintenance program. Periodically, you should check
all equipment for loose connections, burned or pitted
contacts, and the improper mounting of switches. You
should also check for bad connections, improper
mounting, and loose or broken insulators on coils or
Identifying and locating problems within circuits,
appliances, and equipment is a challenging job. This
phase of your rating as a Construction Electrician (CE)
working within a maintenance shop is where much of
your career will be spent.
The inspection and maintenance of switches and
elements on appliances and equipment 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.
To locate faulty conditions in circuits, you need to
perform some inspecting, some calculating, and some
instrument testing. A few moments spent studying the
schematic or drawing of a particular circuit before the
actual troubleshooting begins often simplifies the task
of isolating the trouble. THINK! If a circuit fails to
operate properly, apply some logical reasoning when
you check for the fault. The trial-and-error method is
inefficient and time-consuming.
A bad appliance should first be checked visually. If
you fail to find the trouble by visual inspection, you will
find that a meter is an indispensable device in testing
electrical circuits of appliances.
Power Supply and Cord
When you troubleshoot a circuit, the first thing you
want to do is study the schematic; the next step is to
inspect the circuit visually. Check for loose
connections, loose wires, burnt wires, and burnt
components, and check the type of wiring.
When you attempt to repair an inoperative
appliance, do not be in a hurry to disassemble it to find
the trouble. You should first pull the power cord from
the outlet and determine if there is current at the outlet.
If the outlet is energized, inspect the power cord. Next,
examine the plug connections for cleanliness and
tightness. Finally, inspect the power cord for any
broken wires. If the condition of the cord makes it
unserviceable, replace it before going any further in
your troubleshooting procedure.
Careful inspection of electrical components and
Checking the power supply and the condition of the
equipment is essential to preventing fire hazards caused
power cord should be the first thing you do when you
by defects or dangerous conditions. These inspections
attempt to find an electrical fault in an appliance. In a
include checking for cleanliness, normal operation,
number of cases, electrical faults are found in the power
operation under load, tight connections, adjustment,
cord, rather than in the appliance itself. Only when you
and lubrication Always perform a visual inspection
have determined that the fault is not with the power
first. In this inspection, examine the general condition
supply or cord, should you consider troubleshooting the
of the equipment, determine whether it was abused,
internal units. To troubleshoot these units effectively,
dropped, or overloaded or is inoperative because of
you have to disassemble part of the appliance.
continued use. The general condition of a unit can help
you to determine the fault within it.
Testing and maintaining equipment is best
accomplished at the time of inspection. Completing
everything without returning to the area saves time.
Tools and test equipment should be taken to the job site
when the inspection is performed.