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Model 922 Switch Heater Controller
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The Model 922 Switch Heater Controller is a complete system which provides all necessary control features for electric heating devices on track switches. High and low heat levels, controlled by a rail temperature switch, allow use of high wattage heaters for fast, effective clearing of snow and ice under the most extreme conditions and yet allow reduced energy levels under milder conditions.
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Model 922 Switch Heater Controller
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The Model 922 controller is ready to be installed and operated. Individual fault detection and temperature control has been combined in a simple, reliable, and low cost package. The modular design allows standardized components for single phase or three phase power and single or multiple switch applications.
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All components have been selected for their rugged design and capability to withstand the most severe operating conditions. All current carrying components are oversized by 25% beyond our nameplate rating. The Model 922 controller has been designed to deliver many years of dependable, effective snow melting operations.
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All control features necessary for switch heater operation are standard in the Model 922 controller. Many additional options and configurations are available from Railway Equipment Company.
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FEATURES:
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Main Control Section
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Incoming main circuit breaker
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Remote/local enable circuit
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Rail temperature control circuit
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Reply indication circuit (either 24VDC or closed contact)
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Cabinet space heater
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Air temperature control
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Optional plug-in Snow Detector
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Output Section
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Heater fault-to-ground detection
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Open (non-working) heater detection
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Output contactor
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Heater fault test circuit
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Output fuses
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Time delayed startup (on multiple switch units)
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Status indicating lights
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SPECIFICATIONS:
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Voltage: 208, 240, 480 VAC 1Ø or 3Ø
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Output capacity: 100 amp maximum per output section
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Switches: 12 maximum per controller
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Heater fault range: 150 mA minimum, 800 mA maximum
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Air temperature switch: -30º F to +100º F, normally set at +38º F
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Rail temperature switch: +100º F low point, +125º F high point
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PERFORMANCE:
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TEMPERATURE CONTROL
The 922 Switch Heater Control is turned on by a closed contact, normally a relay closure from a dispatcher, or by the manual switch. If the air temperature is below the 38º F setpoint, the heater will turn on. During normal operation an indication relay provides a closed contact.
The rail temperature range is normally 100º F low setpoint to 125º F high setpoint. An air temperature switch is also used to turn the unit off when air temperature is above setpoint, normally 38º F.
A snap action type temperature switch, mounted on the rail, controls heating. When the rail temperature reaches its high setpoint, the electricity is switched to a half-wave output, thus reducing the heating level. If the rail cools down to the low
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setpoint, the electricity is switched back to full output.
FAULT DETECTION
Each individual switch is monitored for heater fault-to-ground conditions. A fault-to-ground condition will cause the output contactor for that switch to open. In addition, the reply circuit will indicate the fault, and a light on the output section will indicate which switch has the fault. Fault trip levels are individually adjustable and a heater fault tester is provided.
OPEN HEATER
The open (non-working) heater detection circuit monitors each switch for proper heater operation. An open heater will cause the relay circuit to indicate a faulty condition.
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