You're right, finding a true "off-the-shelf" solution for that specific combination of voltage, current, and control requirements can be tricky. Here's a breakdown of where to look and some potential solutions, keeping in mind that you might need to combine components

Challenges:
High Voltage/Current

480V, 400A is a substantial load, requiring robust switching components.

35kA SCCR

The 35kA short-circuit current rating is a significant safety consideration. The device must be rated to withstand that level of fault current.

Manual Override

The requirement for both remote and manual operation adds complexity.

Off-the-Shelf

The term "off-the-shelf" is difficult to achieve for such a high-power application.

Potential Solutions and Approaches


Motorized Transfer Switches (MTS) with Bypass



Description

These are often used for generator transfer applications, but they can be adapted. A key feature is that many have a manual override lever or mechanism in addition to remote operation.

Manufacturers

Look at ASCO (now part of Schneider Electric), Eaton, ABB, Thomson Power Systems.

Caveats

Confirm the SCCR rating of the MTS meets or exceeds your 35kA requirement. You may need to use upstream current limiting fuses or breakers to achieve the desired SCCR. Pay close attention to the control voltage. Ensure it can be easily adapted to your 12-24V DC control signal. Often, you can use a relay interposing relay to convert from 12-24V DC to the MTS control voltage. Make sure the manual operation is truly "manual" and independent of the motorized system (i.e., it works even if the control power is lost).

Why it's a good option

The MTS is designed for switching between two sources. In your application, one source can simply be "off."2.

Combination of Disconnect Switch and Motor Operator



Description

This involves selecting a heavy-duty disconnect switch (480V, 400A, 35kA SCCR) and then adding a separately purchased motor operator.

Manufacturers



Disconnect Switches

Eaton, ABB, Schneider Electric/Square D, Siemens.

Motor Operators

Search for motor operators specifically designed to work with the chosen disconnect switch.

Caveats

Compatibility is key. The motor operator must be designed to work with the specific disconnect switch. Wiring and integration are your responsibility. You'll need to ensure the control circuitry works with your 12-24V DC and provides the necessary control signals to the motor operator. Ensure the assembly as a whole has the required SCCR rating.

Why it's a good option

It can be more flexible and potentially more cost-effective than an MTS, but requires more engineering and integration effort.3.

Contactor with Manual Override



Description

This involves using a large 480V, 400A contactor with a coil voltage that can be easily controlled by your 12-24V DC signal (perhaps through a relay). You would then integrate a heavy-duty, manually operated disconnect switch in series with the contactor to provide the manual override.

Manufacturers



Contactors

ABB, Siemens, Eaton, Schneider Electric/Square D

Disconnect Switch

See list above.

Caveats

The contactor's SCCR may not be sufficient on its own. Consider using current-limiting fuses upstream of the contactor and disconnect switch. The disconnect switch will add a separate SCCR rating for the combined system. The disconnect switch must be rated to interrupt the full load current, even if the contactor fails to open. You'll need to design the control circuitry to ensure proper operation (e.g., preventing the contactor from closing if the disconnect switch is open).

Why it's a good option

Contactor-based solutions can be the most economical, but require careful design and integration.

Crucial Considerations



Safety

This is a high-voltage, high-current application. Any solution must be installed and maintained by qualified personnel.

SCCR Verification

Carefully verify the SCCR rating of the entire system, including all components and any upstream protective devices. Consider using current-limiting fuses if necessary to achieve the required 35kA rating.

Code Compliance

Ensure the installation meets all applicable electrical codes (NEC in the US, or equivalent in other countries).

UL Listing/Certification

If required for your application, ensure that the components or the assembled system are UL listed or certified to relevant standards.

Control Circuitry

Design the control circuitry with safety in mind. Consider adding interlocking features to prevent accidental operation.

Interposing Relays

In nearly every option above, you'll need to use an interposing relay to convert your 12-24V DC control signal to the voltage required by the main device (e.g., 120V AC for the coil of a contactor or the control circuit of an MTS).

Where to Start Your Search


Contact Major Electrical Equipment Distributors

Talk to distributors who specialize in industrial electrical equipment (e.g., Graybar, Rexel, Grainger). They can help you find components that meet your specifications and advise you on potential solutions.2.

Manufacturer Websites

Visit the websites of the manufacturers listed above (ASCO/Schneider Electric, Eaton, ABB, Siemens, Thomson Power Systems) and use their product selectors to narrow down your options.3.

Application Engineers

Contact the manufacturers directly and speak with their application engineers. They can provide technical assistance and help you select the right components.

Example Search Terms: "Motorized Transfer Switch" "Automatic Transfer Switch" "Remote Controlled Disconnect Switch" "Load Break Switch with Motor Operator" "High Current Contactor"Good luck with your search! Remember to prioritize safety and code compliance. Flag for review