This is a tricky situation. Here's a breakdown of how I'd approach it and why

Why Getting the Vendor's Input Specs is Absolutely Crucial
Safety & Compliance

The single-to-three-phase converter is not a standard motor. Assuming a single-phase input current based solely on the motor nameplate is a dangerous oversimplification. The converter introduces significant inefficiencies and non-linear loads, and the single-phase current draw will be higher.

Accurate Load Calculation

Your electrical service and feeder sizes must be based on the actual load presented by the elevator controller. Underestimating this load can lead to overloaded circuits, nuisance tripping, and potentially dangerous overheating.

Code Compliance

You're responsible for ensuring the electrical design meets the NEC. You can't responsibly do that without accurate input information.

Warranty & Liability

If you base your design on estimated values and something goes wrong, the elevator vendor will likely point to your incorrect calculations as the source of the problem. You could be held liable.

Why Using NEC Table 430.248 is a Bad Idea in This Case Table 430.248 is for single-phase motors, not single-to-three-phase converters. The table values represent the actual motor current draw for a single-phase motor of that HP rating. They don't account for the losses and operational characteristics of a converter. Converters are less efficient than direct-drive motors. This means the single-phase input current will be significantly higher than the equivalent HP rating from Table 430.248. You'd be undersizing your wiring. Potential for Harmonic Distortion

The converter will likely generate harmonic currents on the single-phase input. These harmonics can affect the performance of other equipment on the electrical system and may require additional mitigation measures (e.g., harmonic filters). Table 430.248 doesn't address harmonics at all.

Recommended Action1. Strongly Advise Against Stamping Drawings Without Information This is the most responsible course of action. State your case clearly in writing to the owner. Explain the reasons why using estimated values is unacceptable and the potential consequences. Documentation

Keep a record of all communication with the vendor and owner. Document your requests for information and their lack of response. This protects you if problems arise later.2.

Elevate the Issue If the elevator vendor is unresponsive, escalate the issue to their management or the owner's project manager. Make it clear that you cannot complete the electrical design without the required information.3. Consider Alternatives (Only as a Temporary Measure, and with Explicit Disclaimers) Contact Other Converter Manufacturers

Try to find specifications for similar single-to-three-phase converters from other manufacturers. This might give you a ballpark estimate, but it's still not a substitute for the vendor's data.

Assume Worst-Case Scenario

If you absolutely must proceed with a preliminary design, grossly overestimate the single-phase input current. Double or triple the value from Table 430.248. Use larger wire sizes and over-sized circuit breakers. This approach will be more costly, but it provides a greater margin of safety.

Add Explicit Disclaimers

If you provide a design based on estimated values, include very clear disclaimers on the drawings and in your written documentation. State that the electrical design is preliminary and subject to change once the vendor provides the correct input specifications. Emphasize that the owner is responsible for any costs associated with revisions to the electrical system.

Example Disclaimer

"This electrical design is preliminary and based on estimated values for the elevator controller's single-phase input requirements. The elevator vendor has not provided this information. The final electrical design, including wire sizes, conduit sizes, and overcurrent protection, is subject to change based on the vendor's actual specifications. The owner is responsible for any costs associated with revisions to the electrical system due to discrepancies between the estimated values and the actual specifications.*"

In summary, your primary responsibility is to ensure a safe and code-compliant electrical design. You cannot do that without accurate information from the elevator vendor. Push back strongly, document everything, and protect yourself by adding clear disclaimers if you're forced to proceed with limited data. Flag for review