MCB and Fuses


bob peterson

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.
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.

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.