Rockwell Automation 1755-OF8 GuardPLC Controller Systems - Manual (Page 46)

46 Publication 1753-UM001C-EN-P - March 2010
Chapter 3 General Wiring Considerations
The 24V DC voltage supply must feature galvanic isolation because
inputs and outputs are not electrically isolated from the internal
processor.
(1)
To comply with CE Low Voltage Directives (LVD), you
must use either an NEC Class 2, a Safety Extra Low Voltage (SELV) or a
Protective Extra Low Voltage (PELV) power supply to power the
GuardPLC controller or I/O module. A SELV supply cannot exceed
30V rms, 42.4V peak or 60V DC under normal conditions and under
single fault conditions. A PELV supply has the same rating and is
connected to protective earth.
Ground the Equipment You must provide an acceptable grounding path for each device in
your application. For more information on proper grounding
guidelines, refer to the Industrial Automation Wiring and Grounding
Guidelines, publication
1770-4.1 .
Considerations for Grounding All Controllers
•
To improve EMC conditions, ground the controller.
•
Run the ground connection from the ground screw of the
controller to a good earth ground. Use a minimum of 2.5 mm
2
(14 AWG) wire.
•
Keep the connection to earth ground as short as possible to
minimize resistance.
•
Grounding is required even if the control system does not have
shielded cables.
•
If you use shielded cables to connect the controller to the
external 24V DC source, connect the shield to the grounding
contact of the power supply.
•
No protective grounding (against hazardous shock) is required.
GuardPLC 1200 Controller
Ground the GuardPLC 1200 controller by connecting the PA terminal,
marked
, to earth ground. See page 58 for GuardPLC 1200 terminal
connections.
(1) The I/O and CPU are only isolated from one another on the GuardPLC 2000 controller.
IMPORTANT
Protect the controller with a slow-blow fuse.