You've hit on a critical point regarding 314.28(A)(2) and how it relates to splices. The key is the intent of the rule, which is to prevent excessive pulling tension and bending stress on unspliced conductors during installation.Here's a breakdown: 314.28(A)(2) is PRIMARILY concerned with unspliced, continuous conductors. The rule is about the physical stress placed on conductors as they are being pulled through the raceway and into the box. The "sameness" of the conductor, in this context, means a continuous run before any splice is made. Once a conductor is spliced within the box, it's no longer a single, continuous conductor for the purposes of the 6x rule in 314.28(A)(2). The splice effectively breaks the continuous conductor into separate segments. The pulling stress is no longer transferred across the splice. Table 312.6(A) & (B) Applies! As you correctly point out, if the conductors are spliced, and all entries are opposite a removable cover, the minimum dimensions specified in Table 312.6(A) become the governing requirement. These table dimensions are related to wire bending space, and not the physical pulling stress when conductors pass thru the box, therefore, they are less stringent. Your Example

Yes, your scenario of a 6x6x4 box with two 2" conduits entering the back, spliced 4/0 conductors, and a removable cover could be compliant with the NEC as far as pullbox requirements go. You would need to verify that: The 4/0 conductors are appropriately rated for the application (ampacity, temperature rating, etc.). The box is listed for use with 4/0 conductors. The bending radius of the 4/0 conductors within the box does not violate the insulation requirements (generally 6x diameter), and that they are in accordance with 312.6(B). The box is properly sized to accommodate the splices and comply with 314.16, regarding the number of conductors within the box. All hardware installed correctly and listed per the type and size conductors.

Commercially Available Boxes

Yes, enclosures with one removable side are commercially available. They are sometimes referred to as "lay-in" boxes or "wireway connectors". However, a typical 6x6x4 box with one removable side would not meet the requirements you stated to apply Table 312.6(A). That said, boxes with one removable side are available in larger sizes.

Important Considerations



Practicality

While your scenario might technically comply with the NEC, it's worth considering the practicality of working with such a small box. Making neat and reliable splices with 4/0 conductors in a confined space can be challenging. Often a larger box simplifies the installation and improves long-term reliability.

Accessibility

Consider the accessibility of the splices for future maintenance or troubleshooting. A larger box makes it easier to access and work with the connections.

Workmanship

The NEC requires installations to be completed in a neat and workmanlike manner (110.12). A cramped box with tangled conductors might raise questions about compliance with this general rule.

Local Amendments

Always check with your local authority having jurisdiction (AHJ) for any local amendments or interpretations of the NEC. Some jurisdictions might have stricter requirements for pull boxes and splice boxes.

In Summary

You are correct in your assessment. The "6x rule" in 314.28(A)(2) is primarily concerned with unspliced conductors. Once conductors are spliced, Table 312.6(A) often becomes the controlling factor, provided all entry conditions are met. However, remember to consider the practical aspects of the installation, workmanship, and any local requirements.

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