How to Troubleshoot Electrical Grounding Issues in Commercial Buildings

Introduction

Grounding issues in commercial buildings can cause a variety of electrical problems that range from minor annoyances to serious safety hazards. As the building owner, it is critical that you understand the principles of proper grounding and are able to effectively troubleshoot grounding problems when they arise. In this comprehensive guide, I will walk you through the key aspects of electrical grounding in commercial buildings and provide actionable steps for diagnosing and resolving common grounding issues.

Understanding Electrical Grounding Fundamentals

To troubleshoot grounding issues, you first need to understand the purpose and function of grounding systems. Here are some key principles:

• Grounding provides a safe path for electric current. If a short circuit or other issue occurs, the grounding system provides a low resistance path for current to safely flow to earth. This prevents electric shock hazards.

• The grounding system connects equipment enclosures, raceways, and circuits to earth. This equalizes voltage between grounded objects and eliminates voltage differences that could be dangerous.

• Grounding limits overvoltages caused by lightning strikes or utility surges. The grounding system dissipates excess current into the earth.

• A proper equipotential ground plane ensures all grounded objects in a building are at the same voltage potential. This prevents current flow between grounded elements.

• The grounding system must provide a low impedance path to earth. Use of too-small conductors or poor soil contact can compromise grounding effectiveness.

Understanding these key functions will help guide your troubleshooting approach.

Common Signs of Grounding Issues

Here are some of the most common indicators that your commercial building may have deficient grounding that requires troubleshooting:

• Tingle sensations or small shocks when touching appliance enclosures or plumbing fixtures

• Frequent tripping of GFCI or AFCI breakers without an apparent cause

• Electrical equipment damage during lightning storms

• Unexplained flickering lights or power spikes

• Equipment malfunctions or anomalies when operating

• Corrosion on ground rods, bus bars, or conductors

Paying attention to these signs can allow you to proactively identify and correct grounding problems before a safety incident occurs.

Inspecting the Grounding Electrode System

The grounding electrode system provides the vital connection from the electrical system to the earth itself. Start your troubleshooting by thoroughly inspecting:

Ground Rods

• Verify proper sizing - minimum 5/8" diameter and 8' length for commercial buildings

• Check for corrosion and measure remaining metal thickness

• Confirm rods are adequately spaced - at least 6' apart

• Test resistance to earth using a megger - should be less than 25 ohms

Ground Ring

• Inspect for broken, corroded or undersized conductors

• Look for loose connections and evidence of arcing

• Verify the ring fully encircles the building perimeter

• Measure resistance across multiple points - should be low

Bonding Conductors

• Check for sufficient conductor gauge based on system voltage

• Look for damaged insulation or signs of overheating

• Confirm solid, corrosion-free connections to electrodes

• Measure resistance across bonding points - should be less than 1 ohm

Supplemental Electrodes

• Ensure steel building frame members are properly bonded

• Verify water line and Ufer ground connections are intact

• Inspect lightning protection system conductors

Remediate any issues discovered during this inspection before further troubleshooting.

Checking Main Service Grounding

With the grounding electrode system checked, next assess the main electrical service:

• Verify the grounded conductor (neutral) is properly bonded to the ground bus

• Inspect the main grounding electrode conductor (GEC) for damage and measure resistance

• Check that the main disconnect enclosure is bonded to the ground bus

• Confirm appropriate grounding bushings are installed on incoming service conductors

• Ensure the ground bus is securely connected to the grounding electrode system

• Measure resistance from the neutral bus to remote ground points - should be <5 ohms

Correct any improper connections or high resistance readings at the main service panel.

Testing Feeder and Branch Circuit Grounding

Extend your troubleshooting to the remainder of the electrical system:

Feeders

• Check feeder conduit connections and confirm proper bonding throughout

• Measure neutral-to-ground voltages on each feeder - should be <1 volt

Branch Circuits

• Randomly test receptacles for proper polarity and grounding

• Inspect junction boxes for effective bonding between conduits

• Verify ground wires are properly terminated in all outlets and luminaires

• Check panelboards for secure ground bus connections

• Measure neutral-to-ground voltages at panels - should be <0.5 volts

Remediate any poor connections or voltage disparities discovered.

EvaluatingSite Conditions

Also evaluate how local site conditions may be impacting the grounding effectiveness:

• Perform soil resistance testing around the building perimeter

• Check for excessive concrete encasement of grounding electrodes

• Ensure adequate soil moisture levels to improve conductivity

• Inspect for corrosive elements like salts or chemicals in the soil

• Confirm no non-conductive coatings on ground rods or conductors

• Check that underground cable runs are properly grounded

Mitigate any adverse site conditions present that may compromise grounding performance.

Summary

Thoroughly inspecting the grounding electrode system, main service equipment, feeders, and branch circuits allows you to identify and remedy deficiencies. Evaluating site conditions is also an important troubleshooting step. Taking these actions will help restore proper electrical grounding, preventing safety hazards and equipment damage in your commercial building.