Fuse Protection - AutomationDirect C0-USER-M Manual

Chapter 3: Installation and Wiring

Fuse Protection

Fuse Protection for PLC Input Power
External circuit protection is needed to ensure the safety of service personnel and the safe
operation of the equipment itself. To meet UL/CUL specifications, the input power must be
fused. Fuse the AC side of the power supply that provides the 24VDC power to the CLICK
PLC.
When operating the power supply from a 110/120 VAC system with a grounded neutral,
it is only necessary to fuse the line (L) lead; it is not necessary to fuse the grounded neutral
(N) lead. Select the fuse size based on the input current draw of the power supply. Refer to
Chapter 2 of this manual for specifications of CLICK power supplies.
Fuse Protection for I/O Module Circuits
Input and Output circuits on CLICK PLCs do not have internal fuses. In order to protect
your PLC, we suggest you add external fuses to your I/O wiring. A fast-blow fuse, with
a lower current rating than the I/O bank's common current rating can be wired to each
common. Or, a fuse with a rating of slightly less than the maximum current per output point
can be added to each output. Refer to the I/O module specifications in Chapter 2 to find the
maximum current per output point or per output common. Adding the external fuse does
not guarantee the prevention of PLC damage, but it will provide added protection.
WARNING: The discrete inputs and outputs will be damaged if the signal exceeds the rated voltage.
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CLICK PLC Hardware User Manual, 5th Edition, Rev. F – C0-USER-M