You've stumbled upon a common point of confusion and contention in electrical installations, especially when transitioning between NEC code cycles. Let's break down why the allowance you describe might have been acceptable under the 2012 NEC (and perhaps even accepted by local inspectors since) but is generally not under the 2017 NEC (and definitely not under later editions).

The Core Issue: Using Panels as Raceways

The fundamental issue is whether a panelboard can be used as a raceway. The NEC has become much stricter about this over the years. The relevant section is NEC 312.8, Enclosures for Switches or Overcurrent Devices. Historical Perspective (Pre-2017 NEC)

Older versions of the NEC, including the 2012 edition, were sometimes interpreted more leniently regarding the use of panelboards as raceways if certain conditions were strictly met. These conditions generally included:

Sufficient Space

There had to be ample space for the conductors without crowding.

Fill Requirements

The fill requirements for raceways (the percentage of the enclosure's cross-sectional area occupied by conductors) had to be strictly adhered to.

No Splices

Splices or taps were typically not allowed within the panelboard unless specifically permitted by other sections of the code (e.g., for grounding).

Dedicated Function

The panelboard had to primarily serve as the enclosure for overcurrent devices and switches.Why It Might Have Been Allowed Back Then: Inspectors might have allowed it if the AHJ (authority having jurisdiction) saw that, technically, you were just passing through the panel in a very organized and compliant way, without compromising the panel's functionality or safety. This was especially true if it avoided the need for additional conduit runs and boxes. The inspectors might have felt that the conduit was essentially extended through the enclosure.

The 2017 NEC and Beyond (More Restrictive)

The 2017 NEC, and subsequent editions (2020, 2023), significantly tightened the restrictions on using panelboards as raceways. While 312.8 still exists, the interpretation and enforcement have become much stricter.

Explicit Intent

The intent of the NEC is now much clearer: panelboards are primarily for housing overcurrent protection devices (breakers, fuses) and switches. They are not intended to be general-purpose raceways.

Specific Exceptions

312.8 specifically outlines very limited exceptions. The most relevant exception is conductors entering at the top or bottom of the enclosure and passing through. But this is usually interpreted to apply only to conductors directly associated with the panel's function (e.g., feeders supplying the panel).

Article 314, Junction Boxes and Pull Boxes

The code now directs you to use junction boxes or pull boxes for transitions and for connecting the raceways in a manner that's outside the panel's intended function.Why It's No Longer Recommended (or Allowed):



Safety

Using a panel as a raceway increases the risk of damaging conductors when working inside the panel, potentially leading to shorts or ground faults.

Accessibility

It can make it more difficult to access and work on the panel's components, such as breakers, without disturbing the other conductors passing through.

Heat Dissipation

Overcrowding a panel with conductors can impede heat dissipation, potentially leading to overheating and premature failure of the panel or its components.

Code Compliance

It's simply not in line with the current interpretation and enforcement of the NEC.

Why Your Situation is Problematic (Under 2017+ NEC)



Generator Feeders

The conductors you're describing are generator feeders. While they are connected to the panel via the transfer switch, they are not directly part of the panel's primary function of distributing power from the utility.

Through the Panel

Running those generator feeder conductors through the panelboard enclosure, even if you adhere to fill requirements, is generally considered a violation of the current NEC because it's not a conductor that is supplying the panel.

Confusing Accessibility

If you have to open the panel to service something, now you also are dealing with generator conductors that may or may not be energized, depending on the position of the transfer switch.

Word Play and Inspector Discretion

You mentioned "word play." This is a crucial point. Inspectors have a significant amount of discretion in interpreting the NEC. They can consider local conditions, the specific installation details, and their own judgment to determine if an installation is safe and compliant.

"Technically Compliant, But..."

An inspector might acknowledge that technically you've met the fill requirements, but still reject the installation because it violates the spirit of the code, increases safety risks, or complicates future maintenance.

Local Practices

Some areas have a long history of allowing certain practices, and it can take time for those practices to change, even as the NEC evolves.

Inspector Interpretation

Inspectors are human. They may have different interpretations of the code, especially when dealing with ambiguous situations.

Recommendations


Talk to Your Inspector (Again)

Have a frank and open conversation with your inspector. Explain your understanding of the 2017+ NEC, and ask for specific code references that support their position. Get it in writing if possible.2.

Consider Alternatives



External Junction Box

The best solution is usually to install a junction box or pull box adjacent to the panelboard. Run the generator feeder conductors from the meter socket to the junction box, and then from the junction box to the transfer switch (which is mounted next to the panel). This keeps the generator feeder conductors separate from the panelboard's internal wiring.

Separate Conduit

Install a separate conduit run from the meter socket to the transfer switch, bypassing the panelboard entirely.

New Panel with Gutters

(More involved) Replace the existing panel with one that has integrated wiring gutters or larger wiring space specifically designed for through-feeders. However, this might not be cost-effective.3.

Consult a Qualified Electrician: An experienced, licensed electrician familiar with the current NEC and local practices can provide valuable guidance and ensure that your installation is safe and compliant.In summary, while it might have been acceptable to use the main panel as a raceway for the generator feeders under older interpretations of the NEC, the current trend and best practice is to avoid it. Using a junction box or separate conduit run is the preferred and safer approach to meet the intent of the NEC. Always prioritize safety and compliance with the latest code requirements. Flag for review