Scholar V VAIVA Maintenance & Service Manual 10/2017 Rev.2
12
L.
Electric Resistance Heat Safery Controls.
Included with the electric heat assembly
are built in temperature switches designed to turn power off to the heaters if the
temperature is too high. There are two types of temperature switches. The first
is an auto-reset type that turns power off to the heater if it senses an excessive
temperature. When the temperature drops, power is restored to the heaters. This
auto-reset switch is in the low voltage circuit.
The second type of switch is a line current one time limit switch. If it senses an
excessive temperature, power is turned off to the elements. This switch does NOT
reset when the temperature drops and must be replaced if it activates.
The number and location of both switches is determined by the power supply and the
kW of the heaters.
M.
Programmable Logic Controller (PLC) Microprocessor.
The control logic of the Scholar V is handled by a Siemens S7-1200 1215C
Programmable Logic Controller (PLC). This device is powered by 24 volts DC and has
14 digital inputs, 10 digital outputs, two analog inputs and two analog outputs. The PLC
has a model SM 1231 expansion module which provides four type K thermocouples for
measuring various temperatures throughout the unit.
