Okay, I've reviewed the Eaton TVSS installation manual you've provided, specifically document number IB133012EN. Based on my review and my knowledge of the National Electrical Code (NEC), here's a breakdown of whether or not overcurrent protection is required for a TVSS connected directly to a bus, and the relevant considerations

NEC Requirements for TVSS Overcurrent Protection

The NEC generally requires overcurrent protection for Surge Protective Devices (SPDs, which TVSS is a subset of). However, there are specific exceptions that may allow direct connection to a bus without dedicated overcurrent protection. The most relevant sections of the NEC are: NEC 285.22 (Overcurrent Protection)

This section is the primary requirement for overcurrent protection. It states that SPDs shall be protected by overcurrent protective devices sized in accordance with 285.28, unless the exceptions apply.

NEC 285.22 Exception 1 & 2

These are the most likely exceptions that could apply to your situation. They address SPDs that are specifically designed to be connected without discrete overcurrent protection.

Analysis of Your Situation with the Eaton TVSS

Based on the manual, here's how the NEC likely applies:1. Manufacturer's Instructions are Key

The NEC requires you to follow the manufacturer's instructions. The fact that the Eaton manual shows a direct connection without a dedicated breaker or fuse is significant.2.

Internal Protection

TVSS devices, especially those designed for direct bus connection, often have internal overcurrent and/or short-circuit protection. This protection might be in the form of internal fuses, thermal disconnects, or other current-limiting components. This is alluded to in the Eaton manual.3.

Compliance with Standards

Eaton, as a reputable manufacturer, will have designed this TVSS to meet relevant safety standards (e.g., UL 1449 for SPDs). Compliance with these standards often implies that the device has been tested and certified to safely handle fault currents without external overcurrent protection, if installed according to their instructions.

Specifically, Exception 1 of NEC 285.22 allows connection without dedicated OCPD if

The SPD is "listed as a component without internal overcurrent protection" The SPD is "installed in accordance with the listing."The manual states that the SPD is "Listed to UL 1449 4th Edition." So if it has internal overcurrent protection that would need to be verified. Also, it is important to install the SPD according to the manufacturer's instructions.

Here's what you NEED to do to confirm NEC compliance


Check the Product Listing

Look for the UL listing information for your specific model of Eaton TVSS. The UL listing will specify whether the device is intended for use with or without dedicated overcurrent protection. This information can usually be found on the Eaton website, UL Product iQ, or by contacting Eaton directly.2.

Verify Internal Protection

The Eaton manual may (or may not) explicitly state whether the TVSS has internal overcurrent protection. If it doesn't, contact Eaton technical support and ask them directly if the model is designed and tested to be connected directly to the bus without a dedicated OCPD and if it is in compliance with NEC 285.22 Exception 1 or 2. Get their answer in writing (email is fine) for your records.
3.

Follow Installation Instructions Exactly

Install the TVSS exactly as shown in the Eaton manual. Pay close attention to wire sizes, torque specifications, and grounding requirements.4.

Authority Having Jurisdiction (AHJ)

Ultimately, the final decision rests with the electrical inspector (AHJ). Be prepared to show them the Eaton manual, the UL listing information, and any documentation from Eaton regarding internal protection and NEC compliance.

In summary

It's possible that the direct bus connection without a breaker is compliant with the NEC, if the Eaton TVSS is designed and listed for that type of installation and if it has adequate internal overcurrent protection or meets the requirements of NEC 285.22 Exception 1.

Disclaimer: I am an AI chatbot and cannot provide definitive legal or electrical engineering advice. Always consult with a qualified and licensed electrician and your local electrical inspector to ensure compliance with all applicable codes and regulations. Flag for review