3-28. MAGNETIC MOTOR STARTER AND OVERLOAD RELAY.
General. A line voltage type motor starter connects the motor winding to the power distribution electric control
cabinet at full voltage. It consists of a magnetically actuated contactor, with overload protection. The overload
protection is provided by two current sensitive relays connected in series with the motor windings. If the motor draws
more than normal current, a set of contacts in the starter control circuit is opened. Deenergization of the magnetic coil
opens the starter power contacts and disconnects the motor windings from the power circuit. There are six motor starters
in the electrical control cabinet and each one has two overload relays. These overload relays contain adjustment dials
for +15% or -15% field adjustment of tripping current. It is no longer necessary to change the overload heaters to
eliminate such problems as nuisance tripping in hot weather.
Removal. Remove the two mounting screws (6, fig. 3-12) from the overload relay heater (7) and pull straight out
on the heater to remove it from overload relay (5).
Inspect insulation for cracks and other damage.
Inspect molded support with terminals and the overload relay for signs of overheating and cracks.
Inspect screws for damaged threads.
Inspect movable and stationary contacts and springs for wear on contact points and for weak springs.
(5) Inspect heater for cracks, burned or broken wires, or damaged insulation.
Installation. Position overload relay heater (7, fig. 3-12) in the overload relay (5), and secure it with the
mounting screws (6) end lockwasher.
3-29. HEATER AND VAN BODY WIRING CIRCUIT BREAKER.
General. The circuit breaker for the heater and van body electrical systems is an off-on type switch (fig. 3-13),
located inside the electrical control cabinet. It is a 15 ampere, 3 pole, 125 vac unit in a sealed case.
Cleaning. Clean circuit breaker with a clean cloth.
Inspection. Inspect circuit breaker for cracks in the case and test toggle to make sure it has a distinct snap when