Grounding: The Why and the Quick Check

Why this matters

Grounding is the safety system that does nothing until the day it saves a life. A properly grounded device sits quiet for years; then an internal fault energizes its metal case, and the ground path gives that fault somewhere to go (and trips the breaker) instead of waiting for a person to become the path. Because a missing or broken ground is invisible during normal operation, equipment with no ground works perfectly until it shocks someone. Every trade that touches metal and electricity together has to understand it.

Grounding versus bonding (they are not the same)

These two words get used loosely, but they are different jobs.

• Bonding ties all the metal parts that could become energized together, so they all sit at the same potential. If everything metal is bonded, there is no voltage difference between two things you might touch at once.
• Grounding connects that bonded metal to earth and, critically, back to the system's grounded point so a fault current has a low-resistance path back to the source. That return path is what actually trips the breaker on a fault.

You need both. Bonding alone equalizes but does not clear a fault. Grounding without bonding leaves stray metal out of the safety net.

Why the ground path has to be low resistance

For a fault to trip a breaker, fault current has to flow, and a lot of it. A high-resistance or broken ground path cannot pass enough current to trip the protection, so the case stays energized and the breaker never knows. That is the worst case: a "grounded" device that is not actually clearing faults. The path back to the source must be solid, continuous, and low-resistance, not just "connected somewhere."

The quick check

Do these in order. De-energize and verify dead before working on connections.

1. Visual and physical. Is the ground conductor present, landed on the correct terminal, and tight? Tug-test it. A ground that fell off a corroded screw is the most common find. Look for the bonding jumpers on metal enclosures, and on equipment near water look for the bonding grid.
2. Receptacle tester. A plug-in tester flags an open ground instantly on a standard receptacle. Fast first pass.
3. Continuity to a known ground. With the circuit dead, check continuity between the device's metal case (or its ground pin) and a known good ground point. Near-zero resistance is good. High resistance or open means the ground path is broken somewhere between here and there.
4. Confirm it actually returns to source. A ground that reads continuous to a nearby pipe but is not bonded back to the electrical system can be a false sense of safety (a "bootleg" or isolated ground). Verify the path goes back to the system grounded point, not just to random metal.

The traps that fool techs

• The bootleg ground: someone jumped the ground terminal to neutral at a device to "fix" an open ground. It passes a basic tester but is unsafe and against code.
• Painted or corroded contact: a ground screw on a painted or rusted surface may look connected but not actually conduct. Clean to bare metal.
• Broken continuity mid-run: the ground is fine at both ends you can see but open in a junction between. Continuity testing across the span finds it.
• Water and pools: bonding requirements around pools, spas, and wet locations are stricter and life-critical. A bonding gap there is a drowning or electrocution risk, not just a shock.

What to do when you find a grounding fault

Do not energize equipment with a known ground fault and walk away. Restore the ground: remake the connection, clean to bare metal, replace a damaged conductor, or trace and repair the break. Re-test continuity after. If the install never had a proper ground, that is a real finding to document and correct, not to ignore because "it has worked this long."

References

• NFPA 70 (National Electrical Code) - grounding and bonding requirements, including wet locations.
• OSHA 29 CFR 1910 Subpart S - grounding of equipment.
• Manufacturer documentation - equipment grounding terminals and bonding points.
• See related: Polarity and Why It Matters, Voltage Drop: The Hidden Fault.