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I/O and Fusing - Each Card or Each Point?

I recently inherited a job in the water treatment business. It looks like the previous system designer fused EVERY SINGLE input and output point. This is overkill right? I have never ever fused each point. My design practice has always been to fuse each branch circuit or maybe even each card, but never every point.

What do you do? I know my practice is sound, but I'd like some feedback. I just think this is a HUGE waste of panel space.

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Both scenarios are valid, depending on the requirements. Fusing every IO is more robust, because a single failure will not take down the entire branch.

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My experience of industry is that thigns can go wrong in ways you would never have imagined. The more paranoid your design practice, the longer life your system will have. Field wiring to your instruments may well reach surprising voltage & current levels if it is on the same cable tray as power wiring, and somone drives a forklift through the lot!

 

If you are measuring any power signals, then remember that the fuses are to protect your wiring as well as your instrumentation.

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