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When should I use a MCB and when a glass fuse for a control system?

What is the application? A specific I/O point? Circuit breakers get real expensive if you want to put one on every I/O point.

The application is for a control system with a PLC, Analog & digital IO cards. Input voltage from ups is 110VAC. Supply to solenoids (DO) is 24VDC. Please suggest where I should use an MCB and where a glass fuse and why. Thanks.

I like to use MCBs for anything that is common to a group of circuits, e.g. power supplies, modems, PLC racks, etc. There is nothing worse than blowing a fuse and not having a spare on hand. A breaker can be quickly reset.

Fuses are OK for individual loops.

Note: Avoid the indicating type on 4-20 mA loops, if you blow a fuse the LED indicator will allow about 16 mA then max out, allowing you to think the loop is still OK but could cause tank overflow, etc.

Roy