Introduction and General Description
Avtron Outdoor Resistive Load Bank • Part Number K922AD41523
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The Fault Latch Function is incorporated within the Control System of this Load Bank. The Fault
Latch Function is used to determine failure, whether intermittent or constant. If a fault is detected
for Air Failure or Overtemperature, the load is removed and the proper indicator is illuminated. The
fault is not cleared until the fault is corrected and the FAULT RESET pushbutton is pressed to
unlatch the fault. After resetting, the load will be applied.
Airflow switches S1-S8 are used to monitor the flow of cooling air and are located on
Airfail/Overtemp Assembly panel D36358. These differential pressure switches are electrically
interlocked with the load application controls to prevent load application if a fan is not working
properly. When air failure is detected on any stack, it will de-energize relay K99, disconnecting all
load. Load cannot be reapplied unless the fault is corrected and the FAULT RESET pushbutton is
pressed.
Overtemperature switches S10-S17 are used to monitor the temperature of the exhaust air of each
resistor stack and are located on Airfail/Overtemp Assembly Panel D36358. These switches are
electrically interlocked with the load application controls to prevent load application if a resistor
stack temperature exceeds 375°F. When temperature exceeds 375°F in any stack, it will de-energize
relay K99, disconnecting all load. Load cannot be reapplied unless the fault is corrected and the
FAULT RESET pushbutton is pressed.
Motor overload relays are provided in the motor circuits to shut down the load if an overload
condition exists in the motor circuits. All load circuits will be shut down by an overload condition if
any motor overload relay is tripped. The motor overload relays must be manually reset. The motors
that did not overload will continue to run. Shut down the Load Bank and correct the problem before
restarting the Load Bank.
Two 500 watt heater strips with a temperature switch and one main 5000 watt heater with a
temperature switch are mounted within the medium voltage enclosure. One 500 watt heater strip is
mounted within the low voltage enclosure. An additional 500 watt heater strip is mounted in the
configuration area. These enclosure heaters should be used to prevent problems associated with
condensation. These heaters are required to warm the enclosure and components when the ambient
temperature falls below 20°F (-6°C). The main 5000 watt heater is powered directly from a 480
VAC, 3-phase, 60 Hz source. The 500 watt heaters are powered from the 120 VAC, single phase, 60
Hz, from a 480/120 volt control transformer. The temperature switch is factory-set at 50°F. Refer to
schematic D41648.
RESISTIVE ELEMENTS
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