Omron ZEN Operation Manual page 77

Wiring
Output Wiring Precautions
(1) Output Short Circuit Protection
We recommend adding a protective fuse to all output circuits to
protect the output elements and PCBs from burning if the load
connected to the output terminal short-circuits.
(2) Inductive Loads
When connecting an inductive load to an input, connect a surge
protector or diode in parallel with the load.
The surge protector's components should have the following ratings:
Relay Output
ZEN
Relay Output
(Transistor Output)
ZEN
Relay Output
(Transistor Output)
ZEN
The diode should satisfy the following requirements:
Peak reverse-breakdown voltage must be at least 3 times the load
voltage.
Average rectified current must be 1 A.
OUT
Surge protector
COM
(+)
Diode
(−)
(+)
Diode
(−)
Section 2-2
53