The core principle is:
We bond neutral and ground only once, at the service disconnect. Everywhere else, they must stay isolated.
This appliance cord is incorrect, as the neutral has been bonded to ground with a jumper wire
A bootleg ground happens when the neutral wire is illegally tied to the ground slot to “fake” a safe outlet. In knob-and-tube homes with no real grounding system, a 3-prong outlet that tests fine is almost always a bootleg ground.
In a properly wired system, neutral and ground are bonded only once at the service panel. Everywhere else, whether at an appliance or in a sub-panel, neutrals and grounds must stay isolated. That way, load current flows only on the hot and neutral wires, and the ground remains a dedicated safety path to carry fault current. If you bond them again downstream, return current can travel through the chassis, the sub-panel enclosure, and the grounding system. This creates a dangerous situation where a single fault or an open neutral could energize metal surfaces throughout the home.
1. How it should be (safe system)
- From the panel to the appliance:
- Hot → appliance load.
- Neutral → appliance load return.
- Ground → chassis/frame (no current normally).
- Result: Load current flows only on the hot and neutral. The chassis is bonded to the grounding system, but it stays clean (no current).
2. What happens if you also bond at the appliance
- Now neutral is tied to chassis at both ends: panel and appliance.
- This creates parallel paths for return current.
- Some of the neutral current flows on the chassis and grounding conductors.
- If the neutral opens anywhere upstream, the entire chassis of the appliance (and everything bonded to ground — sinks, water pipes, furnace, etc.) can become energized with line voltage.That’s the deadly part.
3. Why the panel bond is safe, but an appliance bond is dangerous
- At the panel:
- The bond is at the source of power.
- Fault current has a low-impedance path back to the breaker, which trips immediately.
- Normal load current only flows on the neutral bus, not the ground bus.
- At the appliance:
- Neutral carries normal load current.
- Bonding it to ground there means you’ve put load current onto the ground path.
- That turns the safety conductor into an active current carrier.
- Now the chassis, conduit, and even water pipes can sit at dangerous potentials during faults or open neutral conditions.
Rusted subpanel: bonding strap correct, but neutrals and grounds wrongly tied together.
Properly wired 240-volt appliance, with the neutrals and grounds correctly isolated and a strain relief clamp properly installed.
This subpanel is correctly wired, with neutral and ground conductors kept isolated.
Here is a much more detailed example,
