You're right to question this and understand that some current will indeed take that parallel path. Let's break down why and why it's not the major concern it might seem to be

Here's the situation you described:
Service Panel

The neutral bus bar is bonded to the service panel enclosure via a Main Bonding Jumper (MBJ).

Conduit

A metal conduit runs from the service panel back to the meter enclosure.

Meter

The neutral is also bonded to the meter enclosure.

Why a Parallel Path Exists

You've identified the key concept: Because the neutral is bonded at both the service panel and the meter, and these points are connected by a metallic pathway (the conduit and the enclosures), you effectively create a parallel circuit for the neutral current. Current always follows all available paths, proportionally to the inverse of their impedance.

Why Most Current Stays on the Neutral Conductor (and why it's designed to)


Impedance is Key

As you mentioned, the impedance of the metal conduit (especially if it includes multiple connections) is significantly higher than the impedance of the neutral conductor (typically copper or aluminum). Impedance is the total opposition to current flow in an AC circuit, combining resistance and reactance.2.

Resistance Difference

Steel conduit has a much higher resistance per foot than a copper or aluminum conductor of comparable size. Connections within the conduit system (couplings, connectors) add even more resistance.3.

Inductive Reactance

The conduit, being a ferrous metal, introduces inductive reactance (opposition to changes in current). This reactance is higher at higher frequencies (like 60 Hz).4.

Designed for Low Impedance

The neutral conductor is specifically sized to carry the expected neutral current. It's a dedicated, low-impedance path.5.

The "1000% More Resistive" Figure

While the exact percentage varies based on materials, length, and connections, the steel conduit path can easily be orders of magnitude more resistive than the neutral conductor. This means for every amp flowing through the neutral conductor, only a very small fraction of an amp will flow through the conduit.

Why This Isn't (Usually) a Major Problem



Low Current on the Conduit

Because the conduit path is so much more resistive, the amount of current flowing through it is typically very small. It's not designed to carry any significant amount of the neutral current.

Ground Fault Protection

The bonding of the enclosures and conduit is primarily for safety in the event of a ground fault (a hot wire accidentally coming into contact with a grounded metal part). In a ground fault situation, the surge of current seeks the lowest impedance path back to the source (the transformer). The bonded enclosures and conduit provide that path, allowing a breaker to trip quickly and clear the fault.

Electromagnetic Interference (EMI)

A properly bonded conduit system helps to contain electromagnetic fields produced by the current-carrying conductors within. This reduces the amount of electromagnetic interference (EMI) that can radiate from the wiring.

When It Can Become a Problem (and why proper installation is crucial)



Poor Connections

If the connections within the conduit system are loose, corroded, or poorly made, the resistance increases drastically. This can cause a measurable voltage drop along the conduit and potentially lead to stray currents.

Improper Bonding

If the bonding connections at the service panel or meter are loose or missing, it compromises the low-impedance path back to the source for fault currents. This can slow down the breaker tripping time and increase the risk of electrical shock.*

Stray Currents

In rare cases, if there are multiple grounds and long runs of metallic piping, stray currents can become a problem, leading to corrosion of metallic pipes or even voltage potentials on grounded surfaces.

In summary:

Yes, a parallel path does exist in your described scenario. However, the vast difference in impedance between the neutral conductor and the metal enclosure/conduit means that only a small fraction of the neutral current flows through the conduit. The primary purpose of the bonding and grounding system is for safety (ground fault protection) and to provide a low-impedance path for fault currents to quickly trip a breaker. Proper installation and maintenance are critical to ensure the system works as intended. Flag for review