You're right, Kohler and Generac have their own quirks. Regarding multiple ATS with a single generator, and specifically how to handle the 2-wire start signal, here's a breakdown of common practice and potential problems

Common Practice: Dedicated 2-Wire Start Signal to Each ATS
Independent Operation

The most common and generally recommended setup is to run a separate, dedicated 2-wire start signal (and associated common) from the generator controller to

each Automatic Transfer Switch. This allows each ATS to independently decide when to signal the generator to start based on its own utility power sensing. If one ATS loses utility and commands the generator to start, the generator starts. If the other ATS also loses utility, it sends its own start signal. When utility returns to either ATS, it will transfer back to utility, and when both have returned to utility, both will signal the generator to stop. Redundancy

If one ATS's 2-wire connection fails, the other ATS(s) can still operate the generator.

Cleanest Logic

Keeps the control logic simple and predictable within each ATS.

Why Not Interconnect the 2-Wire Start Circuits



Control Conflicts

If you wired the 2-wire start circuits from multiple ATS in parallel to a single generator input, you create a potential for conflicts and unexpected behavior. If one ATS incorrectly calls for the generator to start when utility power is actually present at the other ATS, you're unnecessarily running the generator.

Potential for Backfeed

Depending on the ATS design, there's a potential (though often protected against) for voltage from one ATS's start circuit to backfeed into another ATS, causing unpredictable behavior.

Troubleshooting Nightmare

When something goes wrong (generator starts unexpectedly, won't shut down, etc.), tracing the problem through interconnected circuits is far more difficult.

Key Considerations with Multiple ATS and Kohler Generators


Kohler Controller Compatibility

Ensure the Kohler generator controller is rated for the number of ATS you plan to use. The controller needs to be able to handle the current load from the start circuits of each ATS and the generator. Consult the generator's specifications. Some larger Kohler generators may need an upgrade or special module for multiple ATS support.2.

Voltage Level

Verify the 2-wire start signal voltage is compatible between the generator controller and the ATS. 12VDC or 24VDC is common, but double-check.3.

Wiring Quality

Use shielded wire for the 2-wire start circuits, especially in areas with high electrical noise. Ground the shield at the generator end only.4.

ATS Settings

Make absolutely sure the voltage, under voltage, frequency and time delay settings on each ATS are correct, and match the electrical system needs.5.

Commissioning

Carefully commission the system. Test each ATS independently, and then test them in various simulated outage scenarios to confirm proper operation.

Regarding Generac Utility Sense Issues

You're right about Generac and utility sense. Interconnecting the utility sense wires from multiple ATS on a Generac can create very strange and unreliable results. The root cause is that Generac's logic can get confused by the interconnected signals, leading to false utility failures or preventing the generator from starting or stopping properly.The same is true of Kohler, don't interconnect the utility sense wires.

In summary: For most applications, run separate, dedicated 2-wire start signals from the Kohler generator controller to each ATS. Never interconnect the 2-wire start circuits or utility sense circuits between multiple ATS units.* Carefully configure and commission the entire system.If you have a complex or critical application, consult with a qualified electrician or generator technician experienced with Kohler systems and multiple ATS configurations. They can provide specific guidance based on your setup. Flag for review