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When Circuit Boards are Toast, Part 4

Jun 14, 2011 12:01 PM

We previously looked at how violations of Chapter 3 of the NEC can result in power quality-related damage to equipment. Now we'll look at other ways to find sources of circuit board smoke.

Once you've identified and fixed violations of the NEC (Chapter 2, Chapter 3, and Art. 250 Part IV), you need to look at the system in a different way to identify other systemic problems. Your first step is to obtain the latest one-line diagram of the facility power distribution system. Then walk it down to ensure it is correct.

During your one-line verification walk down, you'll be stopping at panels to read the nametags. While you're stopped:

• Conduct an inspection for the same violations discussed already.
• Use a thermal gun or camera to record temperatures on the vents of dry-type transformers serving those panels.
• Note any load-side driven ground rods; they serve no technical purpose, and they typically indicate a need for proper bonding.
• Examine any power factor correction capacitors for evidence of leakage. Make a note to replace any that are swollen or at an elevated temperature.
• Where you see conductors, look for melted jackets or discoloring.

Once your one-line is verified, methodically drill down to inspect the feeders the same way. Next, conduct the same inspection on the branch circuits. After you've fixed all identified problems, you're ready to go back and take measurements. We'll look at that in Part 5.

 

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