Okay, let's break down this scenario and address your concerns about grounding and bonding. You're right to be concerned, and it's important to get this right for safety.

Understanding the Situation Old Installation

This is an older installation (1986), so it's likely that current code requirements weren't in place at the time.

Panel Location

Panel is located in a vault fed from pad mount.

Voltage

120/208V, 3-phase, 4-wire.

Feed

Fused disconnect at the transformer, fed by 4 conductors (3 phases + neutral).

No Ground Conductor

This is the critical point. There's no dedicated equipment grounding conductor (EGC) running with the feeders.

RGC Conduit

Galvanized Rigid Conduit (RGC) identified as Ocal.

Ground Rod

Ground rod at the vault connected to a bushing on the RGC conduit and then to a ground bar in the panel.

Addressing Your Questions1. Is the Conduit Considered the "Ground"? Yes, technically, in this configuration, the RGC conduit is intended to serve as the equipment grounding conductor (EGC). However, whether it's doing so adequately and safely is the question. This practice was more common in the past, especially with RGC. The intention was that the rigid conduit provides a low-impedance fault current path back to the source (the transformer). BUT, just because it was intended, doesn't mean it's compliant with current code or that it's the best or safest practice.2. Does 250.64(E) Apply? 250.64(E) discusses the bonding of electrodes, particularly ground rods. It's not directly applicable to the equipment grounding situation you're describing. While the ground rod at the vault is important (more on that below), it doesn't solve the fundamental problem of the missing equipment grounding conductor along the feeder run.

The Problems and Code Concerns Inadequate Fault Current Path

Relying solely on the RGC conduit as the EGC over a "few hundred feet" is a major concern. Conduit connections can loosen over time, corrode, or be compromised, increasing impedance. This high impedance restricts fault current flow. High-impedance ground faults can: Fail to trip the overcurrent protective device (fuse/breaker) quickly. Create dangerous voltage on the conduit. Pose a shock hazard.

Corrosion

Ocal is PVC coated Rigid conduit. It is highly unlikely a grounding bushing would be connected to the exterior of the RGC. The RGC should have been bonded with internal grounding bushings.

Lack of Redundancy

Relying only on the conduit provides no backup ground path.

Voltage Drop

If the conduit is used for the ground path, it can cause voltage drop.

What Needs to Be Done (Code Considerations and Best Practices)

This situation needs to be addressed to ensure safety and code compliance. Here's what I recommend:1. Consult with a Qualified Electrical Engineer/Inspector

This is crucial. Have a licensed professional evaluate the entire system, including the transformer, fused disconnect, conduit run, and the panel in the vault.2.

Ground Resistance Testing

Measure the ground resistance at the vault. This will give you an indication of how well the grounding electrode system is performing.3.

Add a Dedicated Equipment Grounding Conductor (EGC)

This is the best solution. Ideally, run a properly sized copper EGC with the existing conductors from the transformer fused disconnect all the way to the panel in the vault. Size this EGC according to NEC Table 250.122, based on the rating of the overcurrent protective device (fuses) at the transformer. Connect the EGC to the equipment grounding bar in the panel and to the grounding electrode conductor (GEC) connected to the ground rod.4.

Properly Bond the Conduit

Regardless of whether you add an EGC, ensure that the RGC conduit is properly bonded at every connection point (boxes, enclosures, etc.). Use appropriate bonding locknuts or bushings listed for grounding.5.

Address the Ground Rod Connection

The ground rod is important for earth grounding (dissipating fault current into the earth). Ensure the ground rod connection is robust and properly sized according to NEC 250.66.

Why the Ground Rod is Not Enough

A ground rod alone cannot provide an adequate path for fault current to trip the overcurrent protective device. It serves a different purpose: to provide a reference to earth potential and to help limit voltage during lightning strikes or other transient events. The fault current needs a low-impedance path back to the source (the transformer) to quickly trip the breaker or blow the fuse.

In Summary

While relying on RGC as an EGC was sometimes accepted in the past, it's not the best practice, and often doesn't meet current code requirements, especially over longer distances. The most reliable and safest solution is to install a dedicated equipment grounding conductor along with proper bonding of the conduit. Consult with a qualified electrical professional to ensure the installation is safe and code-compliant.

Disclaimer: I am an AI chatbot and cannot provide definitive electrical code interpretations or professional engineering advice. Always consult with a licensed electrician or electrical engineer for your specific situation.* Flag for review