Let's break this down and address the common understanding and application of these rules.

Understanding the Rules 430.22: Motor Circuit Conductors. This section dictates the minimum ampacity of conductors supplying a motor. The core requirement is that conductors have an ampacity of at least 125% of the motor's full-load current (FLC) as listed in Tables 430.247, 430.248, 430.249, and 430.
250. This is a safety factor to account for potential overload conditions. 110.14(C): Termination Temperature. This is the critical section. It deals with the temperature limitations of conductors and terminations. It dictates the maximum temperature rating you can use for your conductor based on the lowest rated component in the circuit.

How it Works Together1. Determine FLC

Find the motor's full-load current (FLC) from the appropriate table in Article 430 (430.247, etc.).
2.

Calculate Minimum Conductor Ampacity

Multiply the FLC by 1.25 (125%) as required by 430.
22. This gives you the minimum ampacity your conductors must have before derating or adjustment for ambient temperature or number of conductors.3.

Address Termination Temperature (110.14(C))

This is the most important step. You

cannot simply choose the 90°C column just because you've adjusted the ampacity in step 2. You must follow 110.14(C). This section says: The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor, or device. Typically, for equipment rated 100 amps or less, use the 60°C column. For equipment rated over 100 amps, use the 75°C column. Important Exception

Equipment specifically listed and identified for use with 90°C conductors is permitted to be used at the 90°C ampacity. This is rare unless you are using a Variable Frequency Drive.4.

Adjust Ampacity for Ambient Temperature and Number of Conductors (if applicable)

If you need to adjust for ambient temperature or the number of current-carrying conductors in a raceway or cable, you start with the ampacity determined in step 3 (based on 110.14(C)) and then apply the adjustment factors from the appropriate tables in Article 310 (310.15(B)(1) and (2)).

Answer to Your Question

No, you cannot automatically use the 90°C column just because you are using the 125% factor from 430.22. The 90°C ampacity is only permitted if ALL the conditions of 110.14(C) are met. Specifically: The equipment (e.g., motor starter, disconnect switch) and the motor terminations must be listed and identified for use with 90°C conductors. This is unusual for standard motors and starters. If the equipment is not rated for 90°C, you are restricted to the 60°C or 75°C column (typically) depending on the equipment's ampacity rating.In most cases, you will be using the 75°C column (or even the 60°C column) even though you've calculated the conductor size based on 125% of the FLC. The 125% factor ensures adequate ampacity, but 110.14(C) ensures that the terminations are not overheated.

Example

Let's say you have a motor with a FLC of 20 amps.1. 430.22

Required conductor ampacity = 20 amps 1.25 = 25 amps.
2.

110.14(C)

Let's assume your motor starter and motor terminations are only rated for 75°C. You must select your conductor size based on the 75°C column in Table 310.16. A #12 AWG THHN conductor is rated for 30 amps in the 75°C column, and so would be suitable.If your equipment was specifically listed for 90°C terminations, you could use the 90°C ampacity (for example using #14 AWG THHN at 25amps), but this is rarely the case in standard motor applications.

Important Considerations Consult the equipment manufacturer's instructions. They will specify the required temperature rating for terminations. "Rule of Thumb" vs. Code

While rules of thumb can be helpful, always refer to the NEC for the final determination.

AHJ

The Authority Having Jurisdiction (AHJ) has the final say. Be prepared to justify your design and calculations.

In Summary: 430.22 ensures you have conductors with sufficient ampacity. 110.14(C) ensures that the terminations of those conductors do not exceed their temperature rating. 110.14(C) is the determining factor in which ampacity column you can use.Always err on the side of caution and follow the strictest interpretation of the code to ensure safety and compliance. When in doubt, consult a qualified electrician or electrical engineer. Flag for review