Okay, let's break down the situation and the electrical code considerations here.

Understanding the Situation 3-Way Switch at a Basement Exit

This is a common scenario, allowing you to control a light from two different locations (presumably the top of the stairs and the basement exit).

Only 14-3 Cable Present

You only have a single run of 14-3 cable coming to the switch location.

Short EMT Conduit Run

You're planning to use a short, 3-foot section of 1/2" EMT conduit.

The Core Question: Can You Sleeve 14-3 Cable in EMT? NEC (National Electrical Code) Perspective

Generally, you

cannot run NM (Non-Metallic) cable, like 14-3 (NM-B), within conduit for the entire run. NM cable is designed for dry locations and needs air circulation for heat dissipation. Exception

The NEC does allow short "sleeves" of conduit to protect NM cable from physical damage. This is primarily where the cable is exposed to potential harm, like where it exits a wall or passes through a potentially damaging area.

Your Specific Case

Since you are talking about only about 3 feet of conduit that is fine to use as protection.

How to Properly Sleeve the Cable

If you are allowed to use the 3 feet of EMT as a sleeve there are some code issues to consider. Secure the EMT

Secure the conduit properly to the framing using appropriate EMT connectors and supports. The code requires supports every 10 feet of EMT.

Important Considerations and Alternatives1. Why EMT at all? Is there a specific reason you're using EMT? If it's just for physical protection, there might be other options: FMC (Flexible Metal Conduit): You can run individual THHN or THWN conductors through FMC. Metal or Plastic Cable Staples/Clamps: Securely staple the NM cable to the framing, keeping it out of harm's way.2. Running Conductors Inside the EMT (Best Practice in Some Situations)

If you are allowed to use the short piece of EMT, consider the possibility of pulling individual THHN/THWN wires through the conduit instead of running the NM cable inside it. This would be code-compliant in most situations. Use 3 conductors (one black, one white, one red) rated for at least 15 amps (14 AWG). Also a bare ground or green ground conductor.3.

Understanding the 3-Way Switch Wiring

* Make sure you fully understand how 3-way switches work. You'll need to identify the "common" terminal, the "travelers," and the neutral wire correctly. If you are not comfortable with the wiring, hire a qualified electrician.

Recommendation1. Check Your Local Codes

The best practice is to

always consult your local electrical codes and/or a qualified electrician. Local jurisdictions may have specific rules or interpretations that apply to your situation.2. Pulling Individual Conductors

If you're allowed, consider using individual THHN/THWN conductors inside the conduit. This is generally a safer and more code-compliant solution.3.

Proper Installation

Ensure you properly secure the conduit and use the correct connectors and fittings.

Disclaimer: I am an AI chatbot and cannot provide definitive electrical code advice. This information is for general guidance only. Always consult with a qualified electrician for any electrical work. Electrical work can be dangerous if not done correctly. Flag for review