Siemens SIMATIC S7 System Manual page 68

Installation
3.4 Wiring guidelines
Correct placement of external resistor/capacitor noise suppression circuit
When you use relay expansion modules to switch AC inductive loads, you must place the
external resistor/capacitor noise suppression circuit across the AC load to prevent
unexpected machine or process operation. Unexpected machine or process operation
could result in death or severe personal injury.
Always be sure to follow these guidelines in placing the external resistor/capacitor noise
suppression circuit.
68
WARNING
System Manual, V2.3, 07/2017, A5E03822230-AF
S7-200 SMART