Yes, your understanding is correct. According to the National Electrical Code (NEC), you can re-identify the neutral (white) wire in your 12/2 Romex to serve as a hot conductor, provided you follow specific guidelines

NEC Requirements and Best Practices:

1. Permitted Use

The NEC generally allows the re-identification of the neutral (white or gray) conductor as a hot conductor only when done in specific circumstances, such as in a cable assembly where you need an additional hot wire, as you do for your motor.2.

Re-Identification Methods



Marking

You must clearly and permanently mark the white wire to indicate it's being used as a hot conductor. Acceptable methods include:

Colored Electrical Tape

Wrap the wire with black or red electrical tape at all termination points, inside the junction box where the splice is made, and inside the motor connection box.

Permanent Marker

You can use a permanent marker to color the wire black or red at the termination points.3.

Where to Mark

You must mark the wire at all locations where it is visible and accessible, including: Inside the junction box where you make the splice from the Romex to the wires that run in conduit. Inside the motor connection box.4.

Grounding is Critical

Ensure the equipment grounding conductor (bare copper wire in your Romex) is properly connected to both the junction box and the motor frame. This is essential for safety.5.

Conduit and Wire Type

Since you are transitioning to conduit, use appropriate THHN/THWN wires inside the conduit. Do not run Romex directly into conduit for the entire run. Splice the Romex to the THHN/THWN wires inside the junction box.

How to Do It (Simplified)


Mount a Junction Box

Install a suitable junction box where the Romex will transition to conduit.2.

Run Conduit

Run conduit from the junction box to the motor connection box.3.

Prepare Wires

Run two appropriately sized and rated THHN/THWN wires (black and red are good choices for clarity) and a green grounding wire through the conduit.4.

Splice in the Junction Box

Connect the black wire from the Romex to the black THHN/THWN wire using a wire connector suitable for the wire sizes (e.g., a wire nut or a lever-type connector). Connect the white wire from the Romex to the red THHN/THWN wire.

Crucially, mark the white wire with black or red electrical tape at both ends inside the junction box to indicate it is now a hot wire. Connect the bare copper grounding wire from the Romex to the green grounding wire that runs through the conduit. Also, connect this grounding wire to the metal junction box itself (if the box is metal).5. Connect at the Motor

Connect the THHN/THWN wires inside the motor connection box to the appropriate terminals.

Make sure to mark the end of the white wire with black or red electrical tape inside the motor connection box as well. Connect the green grounding wire to the motor frame's grounding screw.6. Secure and Test

Secure all connections, close the junction box and motor connection box, and test the circuit (after ensuring it is de-energized first!).

Important Considerations



Wire Size

Make sure the wire gauge (12 AWG in your case) is sufficient for the motor's current draw and the circuit breaker's ampacity. Refer to the motor's nameplate for its full-load amperage (FLA).

Overcurrent Protection

The circuit breaker protecting the circuit must be sized appropriately for the wire gauge and the motor's FLA.

Local Codes

Always check and comply with local electrical codes, which may have additional requirements or restrictions.

Professional Advice

If you are not comfortable working with electrical wiring, it is always best to consult with a qualified electrician. Mistakes can be dangerous and potentially life-threatening.

Why This Works (and is Important)



Functionality

Motors often require two ungrounded (hot) conductors for 240V or other multi-wire circuits. By re-identifying the neutral wire, you can supply the necessary voltage.

Safety

The proper marking is essential to prevent someone from inadvertently treating the wire as a neutral in the future, which could create a shock hazard.*

Code Compliance

Following NEC guidelines ensures the installation is safe and meets legal requirements.

In summary, you CAN use the white wire as a hot, but ONLY if you properly mark it at all termination points and follow all applicable electrical codes and safety practices. If you are unsure about any aspect of this process, please consult a licensed electrician. Flag for review