Okay, let's break this down and address the potential issues and code violations. Your setup presents several concerns that need careful consideration and likely correction.

Understanding the Situation Main Service Cabinet

A 600A breaker feeding two 200A breakers and one 125A breaker. This is common for splitting the load from a single service.

75 kVA Transformer

480V Delta primary, 208V Y secondary. This is a step-down transformer to provide a lower voltage service.

125A Feeder to Transformer

This is where the problems lie.

Missing Ground Wire

No green (equipment grounding) wire in the conduit from the 125A breaker to the transformer is a MAJOR issue.

Unused Neutral

Running a neutral wire to the transformer but not connecting it to the X0 lug is also incorrect.

Separately Derived System (SDS)

The 208V system created by the transformer is an SDS.

Bonding at the Transformer

The transformer should be bonded at X0 to ground, establishing a new system ground.

208V Panel

A separate ground and separate neutral are at the 208V panel, which is correct for an SDS.

Problems and Code Violations1. Lack of Equipment Grounding Conductor (EGC) in the 480V Feeder to the Transformer

This is a serious safety hazard.

NEC 250.4(A)(5) requires an effective ground-fault current path. Without an EGC, if a fault occurs in the conduit or transformer enclosure, there's no low-impedance path back to the source, leading to potential shock hazards and slow breaker tripping. The metal conduit might provide some grounding path, but it is NOT a reliable or code-compliant substitute for a dedicated EGC (green wire or appropriate sized metal conduit).2. Unconnected Neutral at Transformer

Running a neutral wire to the transformer and then not connecting it to X0 is pointless and potentially dangerous. The neutral isn't performing its intended function and could become energized due to inductive coupling or other stray voltages. This is most likely a code violation.3.

Potential Overcurrent Protection Issues

Depending on the wire size in the conduit, the 125A breaker might be oversized. The feeder conductors to the transformer must be protected by an overcurrent device sized according to their ampacity (NEC 240.4). You need to verify the conductor size.

Recommendations1. Install an Equipment Grounding Conductor (EGC)

This is the top priority. The conduit from the 125A breaker to the transformer

must have an EGC. The EGC must be properly sized according to NEC 250.122, based on the rating of the 125A overcurrent protection device. If the conduit is metallic and properly installed, it may be able to serve as the EGC.2. Connect the Neutral to X0

The neutral wire should be connected to the X0 lug of the transformer. This is necessary for proper operation of the 208V system and provides a low impedance path for ground fault current.3.

Verify Conductor Ampacity and Overcurrent Protection

Ensure the conductors feeding the transformer have adequate ampacity for the load, per NEC 310.15 and any applicable derating factors. Verify the 125A breaker is appropriate for the conductor size and the transformer's primary current rating. The breaker should protect the conductors from overcurrent.4.

Review SDS Bonding

Make sure the transformer's X0 is properly bonded to ground with a grounding electrode conductor (GEC) connected to a suitable grounding electrode (ground rod, building steel, etc.) as per NEC 250.30.
5.

Verify 208V Panel Wiring

Double-check that the 208V panel is correctly wired as an SDS, with the neutral isolated from the enclosure and the grounding conductor bonded to the enclosure.6.

Engage a Qualified Electrician

This situation requires the expertise of a licensed and experienced electrician. They can properly assess the installation, perform the necessary corrections, and ensure code compliance.

Do not attempt to fix this yourself unless you are a qualified professional. The risks of electrical shock and fire are significant.

Important Considerations Regarding the Transformer



Transformer Sizing

Is the 75kVA transformer adequately sized for the load it's serving at the 208V panel? You need to calculate the load to ensure the transformer isn't being overloaded.

Tap Settings

Verify the transformer tap settings are appropriate for the incoming 480V voltage to ensure the correct output voltage (208V) is achieved.

Overcurrent Protection

The transformer also requires overcurrent protection on both the primary and secondary sides. The 125A breaker on the primary provides this. There should be suitable overcurrent protection at the 208V panel to protect the secondary conductors.

In summary, your priority should be addressing the missing equipment grounding conductor (EGC) and connecting the neutral at the transformer's X0. After that, have a qualified electrician verify the rest of the installation for compliance with the NEC. Flag for review