Wiring Standard Density (16-Point Or Less) Discrete Modules; Discrete Relay Output Module Protection; High Density (32-Point) Discrete Module Features - GE 90-30 PLC Series Installation And Hardware Manual

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Wiring Standard Density (16-Point or Less) Discrete Modules

There are three basic wiring methods:

Discrete Relay Output Module Protection

Output points on discrete relay output modules that switch an inductive load such as a relay coil,
lamp filament, or solenoid coil should have external protection. This is usually in the form of an R-
C (Resistor-Capacitor) network across an AC load, or a reverse-biased diode across a DC load.
Please see GFK-0898, Series 90-30 PLC I/O Module Specifications, for details.

High Density (32-Point) Discrete Module Features

7-4 Series 90-30 PLC Installation and Hardware Manual – August 2002
Direct Method. Run the wires from the field devices (switches, relays, etc.) directly to the
screws on the modules' terminal boards.
Terminal Strip Method. Mount a terminal strip inside the control enclosure and wire from
the terminal strip to the modules' terminal boards. Then wire field devices to the terminal
strip.
Terminal Block Quick Connect Assembly Method. The Terminal Block Quick Connect
Assembly has three pieces: a faceplate, a cable, and a terminal block. The faceplate snaps onto
an I/O module in place of its normal terminal board. This faceplate has a connector that mates
with the cable. In turn, the cable plugs into a connector on the terminal block. The terminal
block mounts on a DIN-rail in a convenient place in your enclosure. The terminal block is
used for connecting to field devices such as switches and relays. This method saves, on the
average, over two hours of wiring time per module when compared with the Terminal Strip
method. For more information, see Appendix J, "Terminal Block Quick Connect
Components."
There are two types of these modules. One type has a single 50-pin connector on its faceplate,
the other type has a pair of 24-pin connectors on its faceplate (see next two figures).
The dual 24-pin type has LED status indicators. The 50-pin type does not. The LED status
indicators are arranged in four groups of eight across, labeled A, B, C, and D. They are
located at the top of the module (see next figure).
32-point modules are only available in 5, 2, and 24 VDC ratings.
None of the 32-point modules are fused.
These modules are useful in applications where a high count of DC I/O points is required. The
maximum number of I/O points for a Series 90-30 system can be obtained by using a CPU that
supports a total of eight 0-slot racks, and by populating the racks with 32-point modules. The
theoretical maximum number of I/O points possible is calculated by adding the nine available
slots in the CPU rack (the CPU must occupy one slot) to the 70 slots in the seven 0-slot
expansion or remote racks to get a total of 79 slots. Multiply 79 times 32 for a maximum of
2,528 I/O points (only CPUs 350 - 364 support this many I/O points). This assumes that every
slot is populated with a 32-point I/O module. Most practical applications require some slots
for option modules, reducing the number of slots available for I/O modules accordingly.
GFK-0356Q