The NEC requires all conductors to be terminated correctly, and improper termination is a code violation. Here's a breakdown of how the NEC applies to your scenarios and the intent of the code: General Principle: NEC 110.14 Electrical Connections. This is a cornerstone of safe electrical work. It requires all electrical connections and terminations to be: Made with suitable connectors. Properly torqued. Appropriate for the conductors being connected (size, material, insulation type). Made in a manner that maintains the electrical conductivity and mechanical strength of the connection. Terminating a Neutral with a Wire Nut on a Power Cord

This is generally

not permissible under the NEC for permanently wired installations, although it may be allowed for a temporary power supply during construction, maintenance, or repair. The code prohibits a wire nut alone for permanently connecting the neutral conductor of a power cord to the wiring of a display case. Wire nuts are designed for joining solid or stranded building wires within an enclosure. They are generally not listed or intended for the flexible, finely stranded conductors found in power cords. Why it's usually a violation



Suitability of Connector

A standard wire nut is not typically listed or rated for use with the flexible stranding and insulation types found in power cords. The connection may not be mechanically robust or maintain consistent electrical contact over time.

Strain Relief

Wire nuts alone do not provide any strain relief for the power cord. Movement of the cord could loosen the connection or damage the conductors.

Conductor Compatibility

The alloys in the power cord conductors and the building wiring may not be fully compatible (e.g., aluminum and copper), leading to corrosion over time.

Proper Method

The correct way to connect the power cord would be to use a Listed power supply cord connector. These connectors include strain relief mechanisms and a method to ensure a secure connection to the wiring in the display case (e.g. screw terminals, push in connectors).

Unused Conductors and Marking (Future Use)



NEC 400.10 (A)(7) states that flexible cords and cables are not permitted to be installed as a substitute for the fixed wiring of a structure. If you are pulling fixed wiring (e.g., THHN in conduit) and have unused conductors, these should be terminated in an approved manner (e.g., wire connector, terminal block). NEC 408.41 (D) Requires that all unused panelboard circuit breakers or switches (terminals) that are part of a distribution panelboard or other electrical equipment be filled with blanks (fillers). This prevents accidental contact and short circuits.

In Summary

Always terminate conductors according to the manufacturer's instructions and the requirements of NEC 110.14. Using wire nuts to splice the power cord neutral to the building wiring is generally unacceptable for permanent installations. Unused conductors should be terminated safely and tagged or marked if intended for future use.

Important Considerations



Local Codes and Inspections

Always consult with your local electrical inspector. They have the final authority on code compliance in your area. They can provide specific guidance on what is acceptable.*

Manufacturer's Instructions

Always follow the manufacturer's instructions for any electrical equipment or components you are installing.

Disclaimer: I am an AI chatbot and cannot provide electrical code interpretations. Always consult with a qualified and licensed electrician for all electrical work. Improper electrical work can be dangerous and could violate local codes. Flag for review