Okay, this is a challenging situation with some significant NEC violations based on the description. Let's break down the issues, your proposed solution, and explore alternatives

Key Issues & Violations:
Non-Compliance with Parallel Conductor Rules



NEC 310.10(H)

Parallel conductors (3/0 AWG and larger) are required to be the same length, conductor material, insulation type, and be terminated in the same manner. Using both aluminum and copper grounds immediately violates this.

NEC 300.3(B)

All conductors of the same circuit (including the equipment grounding conductor) must be run in the same raceway. This also doesn't seem to be adhered to with ground present in each conduit.

Improper Grounding Conductor Material Mix

Mixing Aluminum and Copper grounding conductors is generally discouraged and should be carefully considered. The terminations need to be compatible with both materials.

Potential for Circulating Currents

Unequal impedance in the parallel runs can cause circulating currents, especially if the conductors are not well balanced between the conduits.

Potential for Inductive Heating

While the absence of ferrous metal reduces the risk of inductive heating, it doesn't eliminate it entirely. If the magnetic fields from the conductors are not balanced, some heating can still occur in metallic components close to the conduits.

Workmanship and Future Maintainability

The overall install appears to have quality issues and may make future troubleshooting more difficult.

Your Proposed Solution (3 Runs in 2 Conduits)



Conduit 1

2 x Phase A, 2 x Phase B, 1 x Phase C, 1 x Equipment Ground.

Conduit 2

1 x Phase A, 1 x Phase B, 2 x Phase C, 1 x Equipment Ground.

Problems with Your Proposed Solution


Voltage Imbalance is Likely

This uneven distribution of phases between the conduits will likely cause a voltage imbalance. The impedance of each phase will vary significantly between the runs due to the different number of conductors per phase in each conduit. This results in unequal voltage drops across each phase, and can affect equipment connected to the load bank.2.

Circulating Currents Will Still Be a Problem

Although you're not using ferrous metal, the unequal impedance per phase between the parallel runs will still drive circulating currents. These currents increase losses, and potentially cause overheating.3.

Improper Grounding

Grounding conductors still present in both runs when NEC requires all circuit conductors including ground to be in the same conduit.4.

Not in Compliance with NEC 310.10(H)(3)

This code article specifies that parallel conductors shall be the same length. While the conduits are the same length and buried in the ground next to each other, this doesn't guarantee the conductors are the same length. The lengths of each conductor should be measured before paralleling.

Alternatives to Consider (Beyond Removal & Repulling - Given Constraints)

Given the restrictions, here's a structured approach, acknowledging the inherent compromises:1.

Prioritize Two Runs



This is the safest and most code-compliant option. Accept the limitation on the adjustable reactor as advised by your engineer. This minimizes the issues of voltage imbalance, circulating currents, and non-compliance. Verify Load Calculations

Double-check the load calculations to ensure two runs are adequate for the anticipated load even under peak conditions.2.

If Three Runs Absolutely Must Be Attempted



Document Everything

Before making any modifications, thoroughly document the existing installation with photos, measurements, and a detailed schematic. This is critical for future troubleshooting.

Measure Conductor Lengths

Before attempting to connect, measure the length of all conductors to verify compliance with NEC 310.10(H)(3).

Improve Phase Balancing (If Possible)

Try to get as close to balanced as possible. Consider moving conductors between conduits, if feasible, to reduce the imbalance:

More Balanced (But Still Not Ideal)

Conduit 1: 1xA, 2xB, 1xC, 1xG; Conduit 2: 2xA, 1xB, 2xC, 1xG. This is still far from ideal, and will likely cause issues.

Neutral Connection

If using three runs with balanced phase arrangements, consider bringing a neutral conductor from the switchgear to the load bank. This will provide a path for harmonic currents and help mitigate voltage imbalance.

Professional Testing & Monitoring

Hire a qualified electrical testing firm to perform a thorough analysis after making any modifications. This must include:

Voltage Imbalance Measurement

Under load, measure the voltage at the load bank and the switchgear to identify any imbalances.

Current Measurement

Measure the current in each parallel conductor to identify any circulating currents.

Harmonic Analysis

Check for excessive harmonic distortion.

Thermographic Survey

Use an infrared camera to identify any hot spots that indicate overheating.

Implement Protective Measures



Overcurrent Protection

Ensure the overcurrent protection (fuses or circuit breakers) is properly sized and coordinated for the parallel conductors. Use the lowest ampacity of any of the conductors.

Ground Fault Protection

Ensure adequate ground fault protection is in place to detect any ground faults caused by the unusual grounding configuration.

Continuous Monitoring

Install permanent monitoring equipment to continuously track voltage, current, temperature, and harmonics. This is crucial for detecting and addressing any problems that arise.

Important Considerations



Consult with Multiple Experts

Get input from multiple qualified electrical engineers experienced in power systems and NEC compliance. The original design and installation have significant issues.

Prioritize Safety

Above all, ensure the safety of personnel and equipment. The potential for electrical hazards is high with a non-compliant installation.

Liability

Be aware of the liability associated with operating a non-compliant system. Document all decisions and justifications.

In conclusion, attempting to use three parallel runs in this situation is highly problematic and likely to violate the NEC and create safety risks. The safest approach is to limit the load and use only two parallel runs. If three runs are absolutely necessary, extreme caution is required, including thorough testing, continuous monitoring, and consultation with multiple experts. Remember to get written approval from the local AHJ prior to operating. Flag for review