Rockwell Automation 1772-LV,D17726.6.1 A and I MNL MINI-PLC-2/15 PROCESSO - Manual (Page 54)

Assembly and Installation
Chapter 3
3Ć34
When the System Power Supply Chassis cannot be directly connected to the
enclosure or the enclosure ground bus, an equipment grounding conductor must
be connected to the terminal labeled “Equipment Ground” on the System Power
Supply’s terminal strip.
Master Control Relay
A hard-wired Master Control Relay, supplied by the user, provides emergency
power shutdown for Controller I/O devices. Since the Master Control Relay
allows for the placement of several Emergency Stop switches in different
locations, it installation is strongly recommended. Typical Master Control
Relay configurations are shown in Figure 3.34 and Figure 3.35.
When any Emergency Stop switch is operated, power to input and output
devices is removed. Power is still supplied to the System Power Supply so that
the Processor can continue to operate even though all of its inputs and outputs
are “powered down”.
NOTE: The Master Control Relay is not a substitute for a disconnect to the
Controller. It is intended for any situation where the operator must quickly
de-energize I/o devices. When replacing any module, replacing output module
fuses or working on equipment within the enclosure, power must be shut off to
the Controller system.
CAUTION: It is the user’s responsibility to install the Master
Control Relay and the Emergency Stop switches. The use must
make certain that relay contacts have sufficient rating for the
particular application. emergency Stop switches must be located
to provide quick and easy access to the operator or maintenance
personnel. Emergency Stop switches must be wired in series.
WARNING: Emergency Stop switches can be monitored as
inputs in the user program but must not be controlled by the PC.
Any Emergency Stop switch must turn off all input and output
devices by de-energizing the Master Control Relay.
Input Power Connection to System Power Supply
AC Line connection is made to the terminal strip located on the front of the
System Power Supply (Figure 3.36). This System Power Supply is
factory-shipped configured for 120V AC operation.