No, that's not entirely correct. While NEC Table 310.15(B)(17) is a valid table for determining ampacity, you have to meet very specific conditions to use it. Here's a breakdown and the correct considerations

Why 310.15(B)(17) is often NOT the right choice (especially in commercial/industrial):
Limited Use

Table 310.15(B)(17) is specifically for

single-family dwellings and feeder conductors in some 120/240V or 120/208V systems where the entire load is calculated per Article 220, Part III or IV. It allows for smaller conductors for the entire calculated load. Important

This usually means you CANNOT use it for typical commercial or industrial installations, or for branch circuits serving general purpose loads within any building. Those loads are typically calculated using Article 220 Parts III and IV but the allowances that are needed for single-family dwellings do not exist.

Voltage Restrictions

The table is only applicable for specific voltage systems (120/240V or 120/208V). 480V systems are not allowed.

Load Calculation Restrictions

The calculation of the load must be performed exactly per Article 220, Parts III and IV, which are focused on dwelling unit loads. Any other load calculation method disqualifies the use of the table.

What you SHOULD be using instead



Most Common: Table 310.16

This is the workhorse table for determining ampacity of conductors. It gives ampacities based on insulation type and temperature rating for conductors in free air or raceway. You must apply correction factors per 310.15(B)(1) for ambient temperature and 310.15(C)(1) for the number of current-carrying conductors in a raceway or cable.

Free Air Ampacity

Table 310.17 (for single insulated conductors rated 0-2000 volts in free air) and Table 310.19 (for conductors 2001-35000 volts in free air). If the conductors are truly in free air, without being bundled or closely spaced, and meet the mounting/spacing requirements of the table, you can use these. However, this is rarely the case in typical electrical installations.

Key Considerations


Load Calculation

How was the load for the circuit calculated? If it wasn't exactly per Article 220, Parts III and IV, you cannot use 310.15(B)(17).
2.

Application

Is this for a single-family dwelling with specific Article 220 load calculations and* the applicable voltage system? If not, 310.15(B)(17) is not allowed.
3.

Ambient Temperature Correction

Always apply the temperature correction factors from 310.15(B)(1) based on the ambient temperature where the conductors are installed.
4.

Number of Current-Carrying Conductors

If the single conductors are in a raceway or closely bundled, you must apply the adjustment factors for the number of current-carrying conductors from 310.15(C)(1). This reduces the ampacity. Neutral conductors are generally considered current carrying conductors if more than 50% of the load is non-linear.

In summary

While Table 310.15(B)(17) exists, it's highly restricted in its application.

The vast majority of the time, especially for 3-phase, 4-wire circuits outside of specific dwelling unit applications, you will use Table 310.16 (or 310.17/310.19 if appropriate and correctly installed) and apply all necessary correction/adjustment factors.

To give you a more specific answer, I need more information about the application of the circuit. Flag for review