Okay, let's break down the grounding bushing requirements for your described 600A service setup, focusing on clarity and the relevant NEC sections.

Understanding the Basics Purpose of Grounding Bushings/Hubs

These are used to effectively bond metal enclosures (like your CT cabinet and gutter) to the grounding conductor system. This ensures a low-impedance path for fault current back to the source, facilitating the operation of overcurrent protective devices (breakers/fuses) and minimizing voltage on metal parts during a fault.

Grounding vs. Bonding

Grounding connects the electrical system to the earth. Bonding connects metal parts together to create a low impedance path for fault current. Grounding bushings/hubs are primarily for bonding purposes in your scenario.

Qualified Person

It's important to note that electrical work should be performed by a qualified person familiar with the NEC and local codes. This information is for educational purposes and should not be considered a substitute for professional advice.

Your Specific Scenario: 600A Service with CT Cabinet and Gutter

Let's analyze each part of your setup:1. CT Cabinet to Gutter (3" Nipple)



NEC Requirement

NEC 250.92(B)(4) is the critical section here. It specifies the methods for bonding service equipment.

Analysis

Because you are using a raceway (3" nipple) to connect the CT to the gutter you must follow the requirements of 250.92(B)(4). A bonding bushing with a jumper to the grounded conductor is the proper way to bond this raceway.2.

Gutter to 200A Service Disconnects



NEC Requirement

Again, 250.92(B)(4) is the governing section if using raceways.

Analysis

Since you are dropping out of the bottom of the gutter into the disconnects, and are likely using metal conduit or nipples to make that connection you will need to follow 250.92(B)(4). A bonding bushing with a jumper to the grounded conductor is the proper way to bond this raceway.

Key Considerations and Best Practices



Grounded Conductor Connection

The bonding jumpers from your grounding bushings/hubs must terminate to the

grounded (neutral) conductor. Material Compatibility

Use grounding bushings/hubs and bonding jumpers that are compatible with the materials of your enclosures and conductors (e.g., aluminum lugs for aluminum enclosures, copper lugs for copper conductors). This prevents corrosion.

Torque

Properly torque all connections according to the manufacturer's instructions. Loose connections create high impedance and defeat the purpose of the bonding.

Inspection

Ensure that the AHJ (Authority Having Jurisdiction) approves your grounding and bonding methods during inspection.

In summary, you will likely need grounding bushings/hubs and bonding jumpers at the 3" nipple connecting the CT cabinet to the gutter, and where you drop into each of the 200A disconnects.Important Reminders



Local Amendments

Always check for local amendments to the NEC. Your jurisdiction may have stricter or different requirements.

Consult a Professional

If you're uncertain about any aspect of your grounding and bonding system, consult with a licensed electrical engineer or master electrician in your area. This is especially important for large services.

Documentation

Keep records of your grounding and bonding system, including conductor sizes, connection types, and torque values. This can be helpful for future maintenance and troubleshooting.*

Safety: Always de-energize equipment before working on it. Follow safe work practices and use appropriate personal protective equipment (PPE).By following these guidelines and prioritizing safety, you can ensure that your 600A service is properly grounded and bonded, protecting people and property from electrical hazards. Flag for review