You're right to be thorough, as the NEC deals specifically with emergency systems and their disconnects. Here's a breakdown of the relevant code sections and what they require

1. Code Allowing a Second Emergency Disconnect (Generator Disconnect):
701.12 Legally Required Standby Systems, Capacity and Source This section generally requires standby systems to have adequate capacity and a reliable source. While it doesn't explicitly mandate a disconnect at the generator, it's the surrounding requirements that lead to it in many cases. 701.12(B) Point of connection (5) Disconnecting Means. Where the transfer switch is in electrical contact with the normal source, the disconnecting means shall be interlocked with the transfer switch to prevent simultaneous interconnection of the normal and emergency sources. 445.18 Disconnecting Means Required for Generators

This section is the most direct. It requires a disconnecting means for generators. The specific requirement in 445.18(A) (for generators of 15kW or larger) is particularly relevant:

445.18(A)

For generators exceeding 15 kW, a readily accessible disconnecting means, lockable in the open position, shall be located either at the generator location or within sight of the generator location. Where the disconnecting means is lockable, the disconnecting means shall remain lockable in the open position whether a lock is installed or not.

In summary

The need for a second disconnect (at the generator) arises from the requirement in 445.18(A) for a disconnecting means readily accessible and lockable at or within sight of the generator itself, particularly for generators exceeding 15kW. The ATS serves as the service disconnect, but the generator disconnect is a separate requirement to de-energize the generator directly.

Why Two Disconnects Are Often Required in Your Scenario

Your scenario involves:1.

An ATS that is the service disconnect

This means the utility breaker inside is the first point of disconnect for the service, as required for emergency systems.2.

A generator not located immediately adjacent to the ATS

Because the generator isn't in sight of the ATS, 445.18(A) necessitates a readily accessible disconnect at the generator location. Firefighters or other emergency personnel need a way to safely de-energize the generator itself without having to search for it.

2. Signage Size

The NEC

does not specify a precise size for signage. Instead, it uses terms like "legible," "durable," and "conspicuous." The AHJ (Authority Having Jurisdiction, typically the local electrical inspector) has the final say on what constitutes adequate size. However, best practice is to use lettering at least 1/2" high and ensure it's easily readable from a reasonable distance (e.g., several feet). Use common sense: if someone has to be within inches to read it, it's not large enough.3. Signage Format and Content (for Generator Location)



700.8 Signals

Article 700 addresses Emergency Systems. Section 700.8 states that: “where the emergency source or emergency system disconnecting means is not readily accessible or is located in an area not generally accessible to unqualified persons, a sign shall be installed at the location of the service disconnecting means that indicates the location of the emergency source and emergency system disconnecting means.”

445.18(B) Marking

Where the generator disconnecting means is not within sight from the generator, the location of the disconnecting means shall be legibly marked on the generator.

NEC Requirements



Legible

Must be easy to read.

Durable

Should withstand environmental conditions (heat, cold, moisture, UV exposure). Engraved plastic, weather-resistant labels, or paint are common choices.

Conspicuous

Placed in a noticeable location.

Examples of acceptable labels"EMERGENCY GENERATOR DISCONNECT LOCATED AT [Specific Location - e.g., 'South Side of Building', 'Room 105', 'Behind Loading Dock']"Or (if the generator disconnect also serves as a service disconnect for the generator)

"EMERGENCY GENERATOR DISCONNECT - SERVICE DISCONNECT - LOCATION: [Specific Location]"

Important Considerations



Local Amendments

Always check for local amendments to the NEC. Some jurisdictions have more stringent requirements for emergency systems and signage.

AHJ Approval

It's wise to discuss your signage plan with the local electrical inspector before installation to ensure it meets their requirements.

Clarity

The goal is to provide clear, unambiguous information to emergency personnel. Overly technical language should be avoided.

In conclusion:

Having two disconnects (one at the ATS and one at the generator) is not inherently required by a single code section for every installation. However, the combination of NEC 445.18 (for generators exceeding 15kW), and 701.12, in the context of a generator that's not within sight of the ATS (the service disconnect), functionally mandates* a disconnect at the generator. This is combined with the requirement to identify the location of the generator disconnect for first responders.Remember to consult with the local electrical inspector and follow all applicable local codes to ensure a compliant and safe installation. Flag for review