Determining The Date Of The Slc 500 Series A Chassis; Master Control Relay - Allen-Bradley SLC 500 User Manual

System Installation Recommendations
66

Master Control Relay

Publication 1747-UM011G-EN-P - June 2008

Determining the Date of the SLC 500 Series A Chassis

The date of the chassis is found within the serial number imprinted on the
chassis nameplate on the right side of the chassis.
CAT
1746 - A7
SERIAL NO.
A7 -1195A1357
Right Side
Month
Year
A hard-wired master control relay (supplied by you) provides a convenient
means for emergency controller shutdown. Since the master control relay
allows the placement of several emergency-stop switches in different locations,
its installation is important from a safety standpoint. Overtravel limit switches
or mushroom head push buttons are wired in series so that when any of them
opens, the master control relay is de-energized. This removes power to input
and output device circuits.
Never alter these circuits to defeat their function, since serious
ATTENTION
injury and/or machine damage could occur.
If you are using a dc power supply, interrupt the dc side rather
IMPORTANT
than the ac side to avoid the additional delay of power supply
turn-on and turn-off. The dc power supply should receive its
power directly from the fused secondary of the transformer.
Connect the power to the dc input and output circuits through a
set of master control relay contacts.
Place the main power disconnect switch where operators and maintenance
personnel have quick and easy access to it. If you mount a disconnect switch
inside the controller enclosure, place the switch operating handle on the
outside of the enclosure, so that you can disconnect power without opening
the enclosure.
SLC 500
RACK
SER
U L
SA
A
® ®
MADE IN U. S. A.