Specifications

2–24 Selecting Your Hardware Components
Publication 1747-6.2
Selecting Surge Suppressors
Most output modules have built-in surge suppression to reduce the
effects of high voltage transients. However, we recommend that you
use an additional suppression device if an output module is being
used to control an inductive device such as:
• relays • motor starters
• solenoids • motors
Additional suppression is especially important if your inductive
device is in series with or parallel to a hard contact such as:
• push buttons • selector switches
By adding a suppression device directly across the coil of an
inductive device, you will reduce the effects of voltage transients
caused by interrupting the current to that inductive device and
prolong the life of the switch contacts. You will also prevent
electrical noise from radiating into system wiring. The diagram
below shows an output module with a suppression device.
OUT 5
OUT 6
OUT 7
OUT 2
VAC/VDC
OUT 0
OUT 1
OUT 3
COM
+ DC or L1
OUT 4
Snubber
AC or DC
Output Module
DC COM or L2
If you connect an SLC 500 controller triac output to control an
inductive load, we recommend that you use varistors to suppress
noise. Choose a varistor that is appropriate for the application. The
surge suppressors we recommend for triac outputs when switching
120V ac inductive loads are a Harris MOV, part number V220
MA2A, or an Allen-Bradley MOV, Catalog Number 599-K04 or
599-KA04, Series C or later.
Consult the varistor manufacturer’s data sheet when selecting a
varistor for your application.