Why is bonding actually so critical if the system is already grounded?

A ground rod alone won't do squat to trip a breaker during a ground fault. I've seen guys rely on a 10-foot rod thinking they're safe, but the earth itself has way too much resistance to act as a fault path. If you have a 120V fault to a metal enclosure and only an 8-ohm ground rod, wich is actually a decent reading for a single rod, you're only pulling about 15 amps trough the dirt. A 20-amp breaker will sit there and hold all day while that box stays energized at nearly full line voltage.

I've seen situations where the lack of bonding led to exactly what you're worried about. There was a guy in a break room once who got hung up on a faulty appliance beacuse the circuit wasn't bonded properly. His buddy had to literally dropkick him off the machine to break the circuit and save his life. It sounds like a joke from a movie, but when the breaker won't trip because there's no path back to the source, physical force is sometimes the only thing left to stop the heart from stopping. Tell your buddy that the ground rod is for lightning and surge protection, not for clearing faults. To clear a short, you need a metal-to-metal connection all the way back to that main service bonding jumper. Without it, you aren't creating a short circuit; you're just making a heater out of the ground rod. everythign metal attached to that system becomes a live part, including the siding on a building or the frame of a trailer. It’s essentially a giant booby trap.

I once found a subpanel in a detached garage where the installer forgot the equipment grounding conductor entirely. The owner complained about feeling "tingles" when touching the faucet while the dryer was running. When I tested it, the plumbing was sitting at 90 volts. If he had been standing barefoot on wet concrete, that tingle would have been a lethal shock. It's the silent stuff that kills you because you don't know the casing is live til you become the **low-impedance path** yourself.

That story about the faucet sitting at 90 volts is terrifying. I’ve definatly felt those wierd "tingles" before when touching the metal sink and the stove at the same time, but I always just figured it was static electricity. Now I’m worried I’ve been living in one of those booby traps. Is there a way for a regular guy to check if the bonding is solid without actually poking around inside the main panel? I want to make sure my kitchen isn't a hazard, but I'm a bit nervous about opening the service box myself.

You can get a rough idea with a multimeter by checking the voltage between neutral and ground at your outlets. Ideally, you want to see near zero volts. If you’re seeing 5V or more, especially under load, you’ve likely got a high-resistance path or a bonding issue somewhere. Those cheap three-prong plug testers are alright for finding a totally disconnected ground, but they don't tell the whole story. They won't tell you if that ground path is beefy enugh to actually trip a breaker. I've seen plenty of 'bootleg grounds' where someone jumped neutral to ground at the outlet—it tricks the tester but leaves the whole casing energized if the neutral ever breaks.

Be careful with those three-prong testers, though. Some DIYers or shady landlords will do what's called a 'bootleg ground' where they just jump the neutral screw to the ground screw on the outlet. The tester will show green lights, but you still don't have a real safety path back to the panel.

If that neutral wire ever breaks, the whole casing of whatever you plug in becomes live. I once saw a kitchen remodel where every single outlet was bootlegged becasue they didn't want to pull new wire thru the plaster. It’s a total death trap that looks perfectly fine to a cheap tester.

I saw a kitchen remodel where they relied on old BX cable armor for the ground, but the casing was so corroded it couldn't carry enought current to trip the 20A breaker. It just started glowing inside the wall during a short.

People forget that bonding is all about the quality of the path. If it's choked by a loose set-screw or paint on a bracket, your breaker is just a decorative switch. You have to ensure those mechanical bonds are torqued down and clean. Even a little resistance can turn a safety feature into a heating element instead of clearing the fault.