Quick Hits

🗓️ MAY 27, 2026
⚡ GROUNDING & BONDING — EP 22

Locknuts & Effective Bonding ⚡
NEC 250.92(B) Explained
joshthesparky4 · Josh The Sparky

⚡ OPENING HOOK
Just because metal parts touch each other doesn’t mean you have an effective bond.

One loose locknut, painted surface, or improper fitting can interrupt the entire fault-current path.

And when fault current loses continuity…

Protection may not operate the way you expect.

🧠 CORE IDEA
⚡ NEC 250.92(B) requires service equipment bonding methods capable of ensuring reliable electrical continuity and an effective fault-current path.

A lot of installers assume locknuts alone automatically guarantee bonding.

But under certain conditions, they may not provide a reliable enough connection.

Especially when dealing with:

⚡ Concentric knockouts
⚡ Eccentric knockouts
⚡ Paint or coatings
⚡ Isolation washers
⚡ Corrosion
⚡ Loose mechanical connections

That’s where additional bonding methods become necessary.

⚡ WHY EFFECTIVE BONDING MATTERS

Bonding exists for one reason:

To carry dangerous fault current safely back to the source.

If continuity is weak or interrupted, fault current may:

⚡ Arc across gaps
⚡ Energize metal enclosures
⚡ Increase impedance
⚡ Fail to trip breakers quickly

At service equipment — where, when available, fault current is highest — it becomes extremely dangerous.

⚡ APPROVED BONDING METHODS

When standard locknuts are not sufficient, NEC 250.92(B) allows methods such as:

⚡ Bonding bushings
⚡ Bonding jumpers
⚡ Listed bonding-type locknuts
⚡ Threaded couplings
⚡ Other approved bonding fittings

The goal is to maintain reliable low-impedance continuity under fault conditions.

⚡ THE 3 GOLDEN RULES OF SERVICE BONDING CONTINUITY

Don’t Assume Metal Contact Is Enough
Mechanical contact alone does not always guarantee an effective bond.

Protect Fault-Current Continuity
Every bonding connection must remain electrically reliable during fault conditions.

Use Listed Bonding Methods When Required
Bonding bushings and approved fittings exist for a reason — especially at service equipment.

⚠️ BIG MISCONCEPTION
“If the raceway is metal, the bonding path is automatically fine.”

Wrong.

Fault-current paths depend on electrical continuity — not just physical contact.

Paint, loose fittings, corrosion, and certain knockout designs can all compromise the effectiveness of bonding.

🔥 WHY IT MATTERS
⚡ Fault Clearing
Weak bonding paths can delay or prevent breaker operation.

⚡ Shock Hazard
Metal enclosures can remain energized during a fault.

⚡ Arc Flash Risk
Interrupted continuity can create arcing and extreme heat.

⚡ Service Safety
Highly available fault current at service equipment demands reliable bonding connections.

📌 CORE TAKEAWAY
⚡ Effective bonding requires reliable electrical continuity.
⚡ Locknuts alone are not always enough.
⚡ Service bonding methods must withstand real fault-current conditions.

⚡ FINAL LINE
Fault current doesn’t care what “looks connected.”

It only follows paths that remain electrically continuous under pressure.

That’s why proper bonding methods matter.

Educational content based on NEC 250 concepts.

Some reference materials were provided through my electrical training program/school and are based on Mike Holt Enterprises resources.

Learn more about electrician resources here:
https://joshthesparky.com
https://tradehog.net
https://necchat.com
https://fasttraxsystem.com/aff/107
https://www.mikeholt.com

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