Chassis energization · EGC bonding · GFCI response — clear flat schematic, color-coded conductors
Illustrated Guide to NEC 2026 Electrical Inspection (Full Access)
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This tool visualizes what actually happens when the non-current-carrying metal parts of electrical equipment — a motor frame, a panel enclosure, a chassis — become energized because insulation has failed inside. A flat, clearly labeled schematic shows a service panel, four distinct color-coded conductors (Line, Neutral, Equipment Grounding Conductor, and Grounding Electrode Conductor), a motor chassis, a ground rod, and a person near the equipment. Select one of three scenarios — no bonded equipment grounding conductor, an EGC-bonded circuit with no GFCI, or a GFCI-protected circuit — then trigger the fault and watch current find its path in real time, with a live readout of fault current, touch voltage, clearing time, and which protective device (if any) responds, all tied back to the governing NEC sections.
• A flat, clearly labeled schematic — a service panel, motor chassis, ground rod, and a person, laid out with generous spacing so every conductor is easy to trace with the eye. • Four distinct, always-visible conductors, each on its own lane with an inline label — Line (light gray), Neutral (white), Equipment Grounding Conductor (green), and Grounding Electrode Conductor (bare copper) running to the ground rod. • Three fault scenarios — No EGC (the earth alone as the fault path), EGC Bonded with No GFCI (a properly bonded low-impedance path clearing via the branch breaker), and GFCI Protected (a Class A GFCI clearing on milliamp-level leakage current). • An animated fault-current overlay that travels along the actual current path in each scenario, so the direction of flow is visible, not just implied by color. • A live readout panel — fault current, touch voltage on the chassis, clearing time, and which protective device actually operated, calculated live from adjustable ground-fault-path impedance and system voltage sliders. • A running event log — a millisecond-by-millisecond timeline of what the fault does in each scenario, and a verdict statement explaining why the outcome was safe or hazardous. • Direct code citations — NEC 250.4(A)(3)–(5) on the required low-impedance fault-current path, NEC 250.4(A)(5)'s prohibition on relying on earth alone, and NEC 210.8 / UL 943's Class A GFCI 4–6 mA trip threshold.
Insulation inside a piece of electrical equipment — winding insulation in a motor, wire insulation inside a panel — can fail from age, moisture, mechanical damage, or overheating, putting the ungrounded (line) conductor into direct contact with the equipment's metal frame. If nothing intervenes, that metal frame is now energized at full circuit voltage even though it is a part no one expects to carry current.
The equipment grounding conductor (EGC) exists specifically to prevent that frame from staying energized. NEC 250.4(A)(3) requires normally non-current-carrying conductive parts of equipment to be connected together and to the electrical supply source in a manner that creates a low-impedance path for fault current — and NEC 250.4(A)(5) requires that path to be effective enough, and low enough in impedance, that it facilitates the operation of the circuit's overcurrent protective device, clearing the fault quickly. Critically, NEC 250.4(A)(5) explicitly states the earth itself must not be relied upon as that path — earth's resistance is far too high and far too variable to guarantee enough current flows to trip a breaker.
Without a bonded EGC, a person touching the energized chassis can become the only low-impedance path available, and body resistance (roughly 1,000 Ω) is nowhere near low enough to draw the tens of amps a standard breaker needs to trip — the shock hazard persists indefinitely. With a properly bonded EGC, fault current instead returns through the green conductor back to the source, and enough current flows to trip the branch-circuit breaker or fuse in a fraction of a second. A ground-fault circuit interrupter (GFCI) goes a step further: instead of waiting for enough current to trip an overcurrent device, it continuously compares current on the line and neutral conductors and trips on as little as 4–6 mA of imbalance — fast enough (about 25 ms, per UL 943 Class A) to interrupt power before a lethal shock can develop, whether or not a low-impedance EGC path exists at all.
• No EGC — demonstrates the hazard NEC 250.4(A)(5) exists to prevent: an energized chassis with no bonded ground path stays energized indefinitely, and a person in contact with it becomes the fault-current path, with no overcurrent device ever seeing enough current to trip. • EGC Bonded, No GFCI — shows the standard protection scheme working as designed: the green EGC gives fault current a low-impedance return path, enough current flows to trip the branch-circuit breaker, and the fault clears in roughly 130 ms, though brief touch voltage exists during clearing. • GFCI Protected — shows the fastest and most sensitive protection layer: a Class A GFCI detects milliamp-level leakage current between line and neutral and interrupts power in about 25 ms, well below the level needed to trip a standard breaker and fast enough to prevent injury.
A ground fault is an unintended connection between an ungrounded (hot) conductor and a grounded object — most commonly the metal, non-current-carrying frame or enclosure of equipment (a chassis, panel housing, motor frame) after internal insulation fails. It differs from a line-to-neutral or line-to-line short in that the current path runs through equipment that was never meant to carry current, and often through the equipment grounding system, or through a person, on its way back to the source.
Earth resistance is highly variable — it depends on soil moisture, composition, and temperature — and is almost always far too high to allow enough fault current to flow to trip a standard overcurrent device. A single driven ground rod typically has a resistance in the tens of ohms; at 120 V, that limits fault current to only a few amps, nowhere near the tens or hundreds of amps a branch breaker needs to see to trip. Relying on earth alone leaves an energized chassis energized indefinitely, which is exactly the hazard the equipment grounding conductor requirement in NEC 250.4(A)(3)–(5) is designed to eliminate.
The EGC (green, or bare, conductor run with the circuit) carries fault current from equipment back to the electrical source so an overcurrent device can operate — it's a low-impedance fault-clearing path, not primarily a connection to earth. The grounding electrode conductor (GEC) instead connects the system's grounded (neutral) point to a grounding electrode, such as a driven ground rod, and its job is stabilizing system voltage relative to earth and providing a path for lightning and other transients — it is not the intended fault-current-clearing path. Both are bonded together only at the main service disconnect (or main bonding jumper location), which is why they must never be confused with each other or bonded again downstream.
A Class A ground-fault circuit interrupter, per UL 943, trips when it senses between 4 and 6 mA of current imbalance between the line and neutral conductors — and does so in roughly 25 milliseconds. A standard thermal-magnetic circuit breaker, by contrast, is sized to the circuit's normal load current (commonly 15–20 A for a branch circuit) and needs a fault current in the tens of amps or more to trip on its magnetic instantaneous element; a leakage current in the milliamp range through a person's body will never come close to tripping it. This is why GFCI protection is required by NEC 210.8 in locations with elevated shock risk — bathrooms, kitchens, outdoors, garages — independent of whether the equipment grounding conductor is intact.
Touch voltage is the potential difference a person experiences between an energized surface they are touching (like a faulted chassis) and the point where their feet contact the ground. In the No-EGC scenario, the full system voltage can appear as touch voltage on the chassis because nothing provides an effective competing low-impedance path. With a bonded EGC, touch voltage is limited to a brief, much lower value during the short clearing time before the breaker operates. With GFCI protection, the exposure time is cut to about 25 milliseconds regardless of the touch voltage level, which is the primary reason GFCIs are effective even when touch voltage itself is not eliminated.
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Illustrated Guide to NEC 2026 Electrical Inspection (Full Access)
✨ Premium ContentA zoomable interactive reader — free preview, then unlock the full set.