How to Troubleshoot Issues with Your Commercial Electrical Panel

As an electrician, troubleshooting issues with commercial electrical panels is an important skill. Being able to quickly diagnose and resolve problems can prevent power outages, save money on repairs, and ensure a safe working environment. Here is a comprehensive guide on how to troubleshoot common issues with commercial electrical panels.

Inspect the Electrical Panel

The first step is to inspect the electrical panel itself. Look for:

• Loose or damaged connections - Tighten any loose wiring connections and replace damaged wires. Loose connections can cause arcing and heat that lead to fires.

• Signs of overheating - Discolored or warped plastic, melted wires, or a burning smell indicate overheating. Overheating is usually caused by overloaded circuits or loose connections.

• Corrosion or rust - Look for green or white corrosion, pitted metal, and rust. Corrosion can cause circuits to malfunction or fail.

• Moisture or water leaks - Water getting into the panel can short circuits. Seal any leaks and dry any moisture before operating.

• Dirt, dust or insect nests - Use compressed air to clean out any debris or nests. They can obstruct ventilation and cause overheating.

• Broken or damaged components - Inspect circuit breakers, fuses, bus bars, and other hardware. Replace anything cracked, burned, or malformed.

Test the Voltage Inputs

Use a multimeter to check the incoming voltage on each phase coming into the electrical panel:

• Set the multimeter to AC Volts. Turn off and lock out the main breaker. Remove panel cover.

• Test phase 1 to ground, phase 2 to ground, and phase 3 to ground. The voltages should match your supply voltage within a few percent.

• If the voltages are significantly low, there may be problems with your utility supply, transformers, or feeder lines. Call the utility company if needed.

• Any missing phase indicates an open conductor to the panel. Check the main feeder wires.

Check the Grounding System

Use a multimeter to validate the grounding in the panel:

• Check continuity from the neutral bus to the ground bus - There should be continuity. No continuity means a broken ground wire.

• Check continuity from each ground bus to the panel enclosure. Tighten or replace ground connections as needed. Proper grounding is critical for safety.

• Measure resistance between the neutral bus and earth ground. Look for a very low resistance reading, less than 1 Ohm. A high reading means the ground electrode conductor has high resistance.

Inspect All Circuit Breakers

Thoroughly inspect each circuit breaker in the panel:

• Open and close breakers to ensure smooth operation. Breakers should snap into the on and off positions.

• Tighten any loose connections. Faulty connections can result in resistance heating and arcing.

• Ensure circuit breakers are properly rated for the wire size they protect. Oversized breakers can fail to trip on overloads.

• Test GFCI and AFCI breakers with their test buttons. Replace any that don't trip. These provide critical protection against shock and fire.

• Thermally scan for any hot spots which indicate a defective breaker. Use an infrared thermometer or thermal imager.

Replace any corroded, damaged, or faulty breakers.

Check Connections and Lugs

Check all wire connections and lugs:

• Verify tightness of each wire connection and lug using a torque wrench. Loose lugs can overheat and cause melted wires or even arcing faults.

• Closely inspect for discolored, melted, or cracked lugs which indicate overheating. Overheating is caused by loose connections.

• Ensure wires are inserted fully and make solid contact with their lugs. Any exposed wire surfaces can arc and overheat.

Verify Proper Wire Sizes

Wire sizes must match circuit ampacities:

• Inspect wires for corrosion, cracked insulation, burns, or other damage. Replace damaged wires.

• Use wire strippers to access wire size markings. Compare markings to breaker amp ratings.

• For large feeder wires, use a micrometer to precisely measure diameter and determine size.

• Upsize any undersized wires immediately before failures occur. Undersized wires overheat.

Thermally Inspect Wires and Connections

Use an infrared camera or thermometer to make a thermal inspection of wires and connections:

• Scan wires looking for "hot spots" which indicate points of high resistance heating.

• Inspect breaker connections, neutral and ground busbars, and wire lugs. Temperature differences of over 30°F indicate an issue.

• Mark any concerning hot spots. Then shut off power and fully inspect those areas for the root cause (looseness, corrosion, undersized wires, etc).

Check for Short Circuits

Short circuits must be identified and resolved quickly. To check for shorts:

• Inspect for signs of overheating like melted wires or discolored/warped insulation.

• Use a multimeter to check for continuity between hot/neutral, hot/ground, and between hot wires. Any readings indicate a short.

• Isolate the shorted circuit and replace any damaged wires or components. Determine the root cause.

• With power off, use a megohmmeter to test insulation resistance between conductors, and between each conductor and ground. Healthy systems will show high megaohm readings. Low readings indicate deteriorated wire insulation or moisture ingress. Replace wires as needed.

Be systematic and thorough when troubleshooting commercial electrical panels. Carefully inspecting connections, testing voltages, checking breakers, and thermally scanning wires will help uncover issues before they lead to outages, fires, or injury. Proactively fixing any problems found will lead to improved safety and reliability.