Railway Equipment 934, Operating Manual

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P/N R9340-0104 33 © 2010 RAILWAY EQUIPMENT CO.
REV B
5/11
B. SNOW DETECTOR OPERATION
NOTE: A snow detector sensing head only detects moisture. With temperature
sensing capability, the HAB unit assumes moisture is due to snow when the air
temperature is below set point.
All operating functions are similar to remote operation with the following
exceptions:
1. INDICATION: During normal operation under snow detector control, the
indication contact across terminal posts 3 and 4 will not be closed. If
indication during snow detect operation is desired, the SELECT SNOW
INDICATION parameter on the SETPOINT menu should be set to ON.
2. TIMED OPERATION: The snow detector has several different time
scenarios. Refer to SETPOINTS Parts C, D, and I for snow detector
set up
3. RUN TIMER: During remote operation, if the snow detector senses
moisture, the unit will operate according to the settings. The unit will then
operate for the duration of the run timer setting.
4. FAULT CONDITION: A fault condition under snow detector control will
cause the indication contact across terminal posts TS-3 and TS-4 to toggle.
C. SNOW DETECTOR MAINTENANCE
The snow detector sensing head contains a small, self-regulating heater that will
melt snow or ice into water. The sensing head relies on moisture to create a low
resistance circuit path. The heater will also cause the moisture to evaporate
within a short period. If the surface becomes non-conductive due to
contamination by grease or oil, the sensing head will not operate. To ensure
effective and dependable snow detector operation, it is important to inspect the
sensing heads frequently and clean them thoroughly if necessary.. Use a solution
of water and mild detergent or isopropyl alcohol to clean the sensing grid. Use a
clean, dry cloth to wipe the grid. Make sure there is no residue left on the surface.