You're right, this is a tricky area, and the interaction between 620.13(D) and 620.14 can be confusing. Here's a breakdown to clarify how to approach this calculation

Understanding the Conflict:
620.13(D) Main Disconnecting Means and Feeder Protective Device for Multiple Elevators. This section is specifically about sizing the main disconnect (the one right at the panel) and its overcurrent protection for a group of elevators. Crucially, it refers you to Figure 620.13 (Informational Note) for guidance. 620.14 Feeder Demand Factor. This table provides demand factors based on the number of elevators on a feeder. This is where your hope for applying a demand factor lies.The conflict arises because 620.13(D) and Figure 620.13 can give different results than directly applying 620.14. The NEC intends for 620.13(D) and Figure 620.13 to override 620.14 in certain situations, namely when sizing the main disconnecting means and its OCPD.

How to Apply the Code Correctly


Sizing the Feeder for the Panelboard

You want to determine the load on the feeder that supplies your 600A panelboard. Here's how to approach it:

Start with 620.14

This is where you'll get your demand factor. You have nine elevators connected to this panel. Use Table 620.14 to find the corresponding demand factor. For nine elevators, it's 0.
65.

Determine the Sum of the Rated Currents

Add up the rated currents of all nine elevator branch circuit overcurrent protective devices (OCPDs). This is your "total connected load" before applying the demand factor. Crucially, do not use nameplate ratings of the equipment. Use the values of the overcurrent protection.



Apply the Demand Factor

Multiply the total connected load (sum of OCPD ratings) by the demand factor from Table 620.14 (0.65 in your case). This gives you the estimated demand on the feeder.

Add other Loads

Don't forget to add any other loads served by this feeder besides the elevators. This could include lighting, receptacles, or other equipment.

Verify Feeder Ampacity

Ensure the calculated demand (elevators + other loads) doesn't exceed the ampacity of the feeder conductors feeding the 600A panelboard. Also, verify the calculated demand is within the rating of the 600A panelboard.2.

Sizing the Panelboard's Main OCPD

This is where 620.13(D) and Figure 620.13 come into play. If you were installing this panel, or upgrading its main breaker, this section would apply. Since you are assessing an existing installation, this is less applicable and should not be part of your calculation.

In Summary

For assessing the load on the feeder supplying your existing 600A panelboard, use

620.14 to apply a demand factor to the sum of the elevator branch circuit OCPD ratings. Add any other loads served by the feeder to this value. 620.13(D) and Figure 620.13 are primarily for sizing the main disconnect and its OCPD, and is less applicable for determining the load of an existing feeder serving a panelboard with multiple elevators. The goal is to ensure the feeder conductors and panelboard are adequately sized for the likely maximum demand, and this is best accomplished using the 620.14 demand factor along with any other loads served by the panelboard.

Important Considerations



Elevator Type

The type of elevators (traction, hydraulic, etc.) can influence their load characteristics. Ensure you have accurate information on the elevator types when determining their OCPD sizes.

Duty Cycle

Elevator duty cycles (frequency of use, travel distance, etc.) significantly impact demand. The demand factors in 620.14 are based on typical elevator usage. If you have reason to believe the elevators have an unusually high duty cycle, consider increasing the demand factor.

Future Expansion

Factor in potential future elevator upgrades or additions when assessing the feeder load.

Engineering Judgment: Always exercise sound engineering judgment when applying these calculations. If you have any concerns, consult with a qualified electrical engineer.By carefully following these steps and understanding the intent of each section of the NEC, you can accurately assess the load on the feeder supplying your elevator panelboard. Flag for review