You're asking a valid question, and your reasoning is sound. The manual's procedure for prolonged outages and generator shutdown is overly cautious in this specific scenario.Here's a breakdown of why the manual suggests that and why you might be okay to deviate from it

Why the manual says to turn off the main service disconnect:
Absolute Certainty Against Backfeed

The primary reason is to eliminate any possibility, however remote, of the generator backfeeding into the utility grid. Even with a well-functioning ATS, manufacturers want to provide the most robust safety instructions to cover all potential failure scenarios. This step ensures 100% that no power could ever flow back to the utility, even if the ATS fails in an unexpected way. This protects line workers.

Simplification of the Process

For a general audience, a simple, foolproof, step-by-step process is easier to understand and follow. It reduces the chances of user error. The manual can't account for every individual user's understanding of electrical systems.

Maintenance/Repair Safety

It's a good practice to isolate the entire load if you're planning any type of maintenance or repair on the generator system itself in the future. The manual aims to create safe habits.

Why you're likely okay leaving the main service disconnect ON



Properly Functioning ATS

A Generac ATS is designed to prevent backfeeding. It's a safety-critical component. If it's working correctly, it physically isolates the generator output from the utility grid during generator operation. When utility power returns, the ATS is supposed to switch back to utility power before the generator is turned off.

Convenience of Automatic Return

As you pointed out, turning off the main service disconnect means you won't automatically have power restored if the utility comes back online overnight. The ATS will remain powered, and in the "Utility" position, but you'll have to manually turn the breaker back on.

Here's a more refined approach, considering your situation


Verify ATS Functionality

First, and most importantly,

ensure your ATS is operating correctly. Observe its behavior during a simulated power outage (if possible without disrupting others) and during the return of power. Confirm that it switches cleanly and as expected. If you have any doubts about its reliability, follow the manual's procedure exactly. A malfunctioning ATS is a serious hazard.2. Normal Shutdown (If You Trust Your ATS)

Allow the generator to run unloaded for a few minutes to cool down (some models have a built-in cooldown cycle). Turn the generator disconnect breaker OFF. The ATS should automatically switch back to utility power when it senses the generator is no longer providing power. Leave the main service disconnect breaker ON.

Regularly inspect and test your ATS to ensure it's functioning correctly.3. Shutdown for Absolute Safety (If You Don't Trust Your ATS or Want Ultimate Assurance)

Allow the generator to run unloaded for a few minutes. Turn OFF the main service disconnect breaker. Turn the generator disconnect breaker OFF.

Important Considerations



Consult a Qualified Electrician

If you're uncomfortable with any of this or unsure about the operation of your ATS, consult a qualified electrician. They can inspect your system and provide specific recommendations for your situation.

Warranty Implications

Check your Generac warranty. Deviating from the recommended procedures might (though unlikely in this case) affect your warranty coverage.

Local Codes

Ensure your generator installation complies with all local electrical codes.*

Testing

Regularly test your entire generator system, including the ATS, to ensure it's working as intended.

In summary: You are correct that leaving the main service disconnect ON is likely safe and more convenient if your ATS is functioning correctly. However, the manual's recommendation is the absolute safest option and the one to follow if you have any doubts. Always prioritize safety when dealing with electrical systems. Flag for review