Okay, let's break down your understanding of GFCIs and EGCs and address your "better" scenario question.

Your Initial Statements



"GFCIs do not need an EGC to operate - they measure current imbalance between L and N and trip when the disparity >= 6mA" - Correct. A GFCI's fundamental function is current imbalance detection. "EGCs provide a low-impedance path to ground to protect users from shock when conductive "stuff" is inadvertently energized (ie. ground-faults)" - Correct. The EGC is designed to carry fault current back to the source, causing the breaker to trip rapidly. "Installing a GFCI in an ungrounded (no EGC) outlet solves the issue of not having an EGC." - This is incorrect and dangerous. While a GFCI increases safety in an ungrounded outlet, it does not replace the function of an EGC. It's a supplemental safety measure, not a replacement.

The Crucial Nuance: The "Better" Operation Question

Yes, there is a situation where the presence of an EGC would make the operation of a GFCI "better," or more specifically, faster and more reliable in preventing a dangerous shock. This stems from the speed and certainty of fault current flow.

Let's Analyze Your Scenarios



Scenario 1: GFCI WITH EGC You're correct. A fault to the case of the appliance will cause current to flow through the EGC back to the source. Crucially, this will likely cause the breaker to trip before the GFCI has a chance to react. A standard 15A or 20A breaker is designed to trip very quickly (almost instantaneously) under a high fault current. The EGC ensures a high fault current. The GFCI acts as a secondary layer of protection. If the breaker doesn't trip fast enough (or fails to trip), the GFCI will still detect the imbalance and trip, preventing a sustained shock. It's a redundant safety system. Scenario 2: GFCI WITHOUT EGC You're also correct that the case is energized at 120V, creating a shock hazard. The Key Problem

The only way the GFCI trips is if there's enough leakage current to ground. This is highly variable and depends on the impedance of the leakage path. This is where the protection becomes much less reliable.

Why this is unreliable



Leakage Path Impedance

The path from the energized appliance case to ground (other than the EGC) is likely to be high impedance. This could be through damp concrete, through a person touching the appliance and a grounded object, etc.

Current Flow

Because of the high impedance, the current that actually flows might be less than 6mA for some time. The GFCI won't trip.

The Dangerous Scenario

A person could be receiving a shock for a prolonged period before enough current leaks to ground to trip the GFCI. Remember, GFCI trips at 6mA and above, but the onset of ventricular fibrillation could occur at 30mA, and death could occur shortly after.

Important Clarification

You say "...if a person can have enough current flow through them to trip a GFCI, why couldn't some other arbitrary device?" The difference is a person completing the circuit. Without a completed circuit, there is no current flow.

The Ground is Not Always a Guarantee

The "ground" in the "leakage to ground" scenario is not a guaranteed low-impedance path. Think of it as capacitive coupling to the earth, or some high-resistance path through concrete, etc. It's not the same as a solid, conductive EGC connection. The ground is far from 0 Ohms to the utility company transformer. It is a higher impedance path.

In Summary



An EGC provides a guaranteed low-impedance path for fault current. This leads to a fast trip of the circuit breaker, minimizing the duration of any potential shock. A GFCI without an EGC relies on uncontrolled leakage current to ground. This is slower and less reliable because it depends on the impedance of the leakage path. The GFCI might trip, but it might not trip quickly enough to prevent a dangerous shock. The EGC will likely trip the breaker before the GFCI ever notices the imbalance (fault) in currentThe Key Takeaway

The presence of an EGC makes the electrical safety system far more effective. It's not just about whether the GFCI will eventually trip; it's about how quickly the fault is cleared. A fast trip is the difference between a startling tingle and a potentially fatal shock.

Regarding GFCI Use in Ungrounded Circuits

While the NEC allows GFCI protection in existing ungrounded circuits (with specific labeling requirements), it is never a substitute for proper grounding. It's a way to add a layer of safety to an existing, potentially hazardous situation, but it doesn't magically transform an ungrounded system into a safe, grounded one. It is a false sense of security.

Your Understanding of Grounding:

I commend you for your interest in grounding. It's a crucial concept for electrical safety. Keep studying and asking questions! Remember, a deep understanding of these principles is essential for anyone working with electricity. It's not just about code compliance; it's about protecting lives. Flag for review