Okay, this is a tricky situation, and the code isn't perfectly explicit on T-bodies in this specific configuration. Here's a breakdown of how to approach it based on the NEC and industry best practices, along with some interpretation and considerations

Understanding the Issue

The problem is that you have a T-body where the total conductor count appearing to pass through (if simply added) exceeds what might be expected based on a strict reading of conduit fill rules, even though no single cross-section violates the fill requirements.

Relevant NEC Sections and Principles1. NEC 314.16(C)(1): Conduit Bodies

This section governs the number of conductors permitted in conduit bodies. It refers you back to conduit fill rules in Chapter 3.2.

NEC Chapter 9, Table 1: Conduit and Tubing Fill Tables

These tables dictate the maximum percentage fill for conduits.3.

General Principle: Do not overload the raceway. The overarching goal is to ensure adequate heat dissipation and prevent conductor insulation damage.

How to Interpret for a T-Body in This Configuration

The NEC doesn't have a perfect, diagram-specific rule for your exact scenario with a T-body. Therefore, we need to combine the code requirements with sound electrical engineering principles. Individual Conduit Sections are OK

You've confirmed that each connected conduit itself is within fill based on the conductors within that conduit. That's a good start.

Cross-Sectional Compliance

You've also confirmed that any cross-sectional slice through the T-body contains conductors that, when summed, don't exceed the fill allowance. This is key.



The "Passing Through" Conductor Issue

The apparent overlap in fill due to the conceptual "passing through" conductor count exceeding the maximum fill becomes the focus, given the two previous points.

What the Code REQUIRES (and doesn't clearly require)



What the Code REQUIRES (and doesn't clearly require)

Based on the provided information, and assuming compliance with the previous two points, the NEC

does not explicitly prohibit your configuration. However, the installation

MUST NOT generate excessive heat or be subject to physical damage.

Recommendations and Justification1.

Document your calculations

Keep a record of the conductor sizes, fill calculations for each conduit, and a drawing illustrating the conductor routing within the T-body. This is helpful for future inspection and maintenance.2.

Derate if necessary

Consider derating the ampacity of the conductors if the combined effect of the conductor density within the T-body could lead to excessive heat. NEC Article 310 provides guidance on ampacity and derating. This is especially important if the conductors are carrying near their rated current.3.

Use Larger T-Body (If Feasible)

If practically possible, using a larger T-body will increase the internal volume and improve heat dissipation.4.

Consult with a Qualified Professional

If you have any doubts or concerns, consult with a licensed electrical engineer or a qualified electrical inspector in your jurisdiction. They can provide specific guidance based on local interpretations and the specific details of your installation.

Example Calculations (Illustrative)Let's assume all conductors are #12 AWG THHN. A #12 AWG THHN conductor has an approximate cross-sectional area of 0.0133 sq in.

Scenario 1

9 conductors in the side entry, 3 go left, 6 go right, plus 3 "pass through." If you simply added all those, it would seem like you have 12 conductors effectively occupying space.

However

Your stipulation is that no single cross-section has more than 9, which is within fill.

Important Considerations

Physical Damage

Ensure the T-body is adequately protected from physical damage.

Accessibility

Ensure the T-body remains accessible for inspection and maintenance.

In summary, while the NEC lacks a precise rule for this specific T-body scenario, your configuration appears to be acceptable if



Each conduit run is individually within fill limits.

No cross-sectional slice of the T-body exceeds fill limits.

You address potential heat buildup with derating, if necessary.

You document your calculations and consult with a qualified professional if needed.Remember to always prioritize safety and adhere to the NEC and any local amendments. Flag for review