ST-47 Groundhog - Technical Manual
General
Page 6.
1.1.3 Deadman Capable Model Description
(Applies to Models ST-47 EL(K)/D) Deadman capable models of the ST-47 differ from standard
models in two ways
1.) The Model ST-47/D requires the use of a Scully deadman equipped plug and cable or
ground ball connector and cable assemblies (Model SC-47CC/D). These include a
hand-operated deadman switch added to a standard plug and cable assembly.
Two additional wires must be run in the intrinsically Safe (I.S.) conduit which connects the
ST-47/D to the plug and cable assembly.
2.) Unlike the standard Model ST-47 there is no volt free permissive contact connected to
TB1 terminals 4 and 5. Only the permissive contact of TB1 terminal 5 can be utilized and it
must be connected to one wire (AC hot) of an inductive or resistive external device. The
other wire of the inductive or resistive external device is connected to AC neutral. In normal
operation, the deadman switch must be operated to “permit” operation of the external
device. When the ST-47 is permissive (green lamp lit), and the deadman switch is operated,
the external device connected to TB1 terminal 5 is energized.
1.2 ST-47 Normal Operation
1.2.1 Status Lamps
Match the state of the front cover indicators on the Groundhog with the chart below. Determine if
the status meets the conditions present and refer to the Troubleshooting Section of this manual if
required.
1.2.2 Use With Scully Ground Bolt or Ground Ball
A front panel mounted red lamp indicates that a safe ground attachment has not been made or,
the ST-47 is not connected to a vehicle. After connection to a vehicle mounted Ground Ball or
Ground Bolt the green lamp on the front panel illuminates indicating that the Scully Groundhog
system is operational and the ground path to the vehicle is complete. A normally open user contact
is provided on TB1 terminals 4 and 5, it should be connected to the permit circuitry at the terminal
loading rack. The permit contacts close when the ground path to the vehicle is veried.
GREEN
LAMP STATUS
RED INDICATION
OFF ON Rack to vehicle, rail tank car, container, etc. ground bond veried.
Output is “Permissive”
ON OFF Rack to vehicle, rail tank car, container, etc. ground bond not veried or unit is
malfunctioning. Output is “Non-Permissive”
OFF OFF 1.) Indicator lamp(s) is/are burned out.
2.) The unit is not powered.
3.) Optional Bypass switch is in OFF or BYPASS position.
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