Troubleshooting Unusual Electrical Grounding Issues in Older Commercial Buildings

As an electrician working on older commercial buildings, I occasionally come across unusual electrical grounding issues that require some troubleshooting to resolve. Here is an in-depth look at some of the common causes and solutions for these types of problems:

Typical Causes of Unusual Grounding Issues

There are a few key factors that can lead to atypical grounding problems in older commercial buildings:

Age and Deterioration of Electrical Systems

• Older buildings often have electrical systems that are many decades old. Over time, the grounding components can deteriorate, corrode, and lose effectiveness. Issues like loose connections, corroded ground rods, and damaged wiring insulators are common.

Multiple Additions and Renovations

• Most older buildings have gone through many renovations and additions over the years. This can lead to inconsistent or inadequate grounding as new sections are added onto old. Separate grounding systems that are not properly bonded can develop.

Use of Metal Piping for Grounding

• In old buildings, electricians often used metal piping like plumbing, gas lines, or heating systems as a source of ground bonding. This can cause issues if piping is replaced with non-conductive materials like PVC over time.

Lack of Proper Grounding Design

• Grounding practices decades ago were less rigorous than today. Older buildings may simply lack a properly planned grounding electrode system.

Typical Unusual Grounding Problems

Some specific unusual grounding issues that can stem from the above causes include:

Ground Potential Voltage Differences

• When grounding points are inconsistent, you can get differing voltage potentials between grounded objects in the building. This can cause equipment issues and shock hazards.

System Grounding But No Equipment Grounding

• In old wiring systems, sometimes only the system was grounded but not the actual devices and equipment. This leads to no ground path back through devices.

Intermittent Ground Faults

• Loose, corroded, or damaged grounding connections can cause intermittent ground faults. These can be challenging to trace.

Unusual Voltages on Equipment Cases

• With poor grounding, electrical current can find its way onto normally non-current carrying equipment housings and frames, posing a shock/electrocution danger.

Tingle Voltages

• When grounding is inadequate, a person can feel a tingle voltage from surfaces that should not be energized, indicating current is flowing through their body to ground.

Tips for Troubleshooting the Issues

When unusual grounding issues are suspected, there are some good troubleshooting techniques to employ:

• Check ground connections for tightness and no corrosion.
• Test resistance on grounding components like rods, bonds, and connections.
• Use a multimeter to check for unexpected voltage on any grounded metal object.
• Try disconnecting certain grounding points to isolate the issue.
• Consult building plans toaudit the overall grounding system.
• Consider using ground fault indicators to detect intermittent faults.
• Check that separate grounding systems are properly bonded together.
• Verify a good, low resistance path from system ground to neutral at the main panel.

In many cases, resolving odd grounding problems in old buildings requires creating a proper grounding electrode system where none exists. That may mean driving new ground rods, establishing new bonding connections, and replacing deteriorated wiring. Reworking the grounding can be labor-intensive but helps avoid many dangers.

Case Example: Tracing Tingle Voltage in a Hospital

I once worked on fixing unusual grounding issues in an old hospital. Users were experiencing tingle voltages on metal surfaces like sinks and cabinets. Using a multimeter, I found higher than normal voltages on those grounded objects.

Examining the blueprints showed that two wings of the hospital, built decades apart, had separate grounding electrode systems. I inspected the main panel and found no bond between the two. Installing proper bonding between the systems and adding new ground rods for good measure solved the issue and eliminated the tingle voltages patients and staff had felt.

Key Takeaways

• Unusual grounding issues in old buildings stem from age, renovations, and flawed original design.

• Key problems include voltage differences, missing safety grounds, intermittent faults, case voltages, and tingle voltages.

• Good troubleshooting involves checking connections, testing resistance, measuring voltages, isolating points, auditing systems, using indicators, and verifying bonding.

• In many cases, a new properly engineered grounding system is required to fix issues for good.