⚡ Code Corner:🔸 NEC 250.96(B) – Bonding for Over 250 Volts

📘 What NEC 250.96(B) says:

What it says:
If you're working on systems over 250 volts to ground, and your metallic raceways or enclosures are relying on concentric or eccentric knockouts, then you must provide a bonding jumper or other listed bonding method to ensure a continuous low-impedance path for fault current.

Why it matters:
If a short circuit happens (say, a hot wire touches the metal box or conduit), the only way the breaker trips fast enough to prevent a fire is if there's a solid, low-resistance path for that fault current to return. Without proper bonding, the fault current might be weak — causing arcing, overheating, or even fire.

💡 Pro Tip: When working on 277/480V systems, always assume that concentric or eccentric knockouts do not meet bonding requirements—even if the fitting seems tight.

✅ Use a bonding bushing with a grounding lug, and land a jumper to the ground bar or grounding electrode conductor.
✅ For services and transformer-fed panels, bonding is even more critical—inspectors are watching.

🧠 Remember: If fault current can’t flow freely, it won’t trip the breaker. That’s when things burn.

🧠 Think it through – Metal raceways are not automatically grounded just by being connected—especially when eccentric or concentric knockouts are used. The NEC requires a low-impedance path for fault current, and bonding jumpers or bushings provide that reliability.