Electrical Troubleshooting Quiz, May 10, 2011

You recently transferred to a plant with high rates of circuit board failure

You recently transferred to a plant with high rates of circuit board failure. Last week, a manufacturer's rep asked, "Are you using these for fuses over there?" The worst news came yesterday when a manufacturer said they had no spares left to send you. This means replacing the entire system, and that's a capital project headache you must fast track because the machine makes a part for a critical customer.

Your job depends on fixing this as quickly as possible. Where should you start?

Power quality problems are highly suspect here. Look for violations of the NEC Chapter 3 wiring methods and Art. 250, Part V, to solve them. One plant reduced astronomical rates of circuit board failure to zero. Among the solutions implemented were:

  • Connect internal strap in distribution transformers.
  • Rewire 480V circuits that were split into different raceway.
  • Remove plastic couplings from EMT runs.
  • Replace paralleled conductors of different sizes with same-sized ones.
  • Remove all indoor ground rods, and bond equipment to the equipment grounding (bonding) system.

Can you locate the NEC requirements for these solutions? If not, you need to spend "power quality time" with the NEC.

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