Okay, let's break down this situation and the best course of action.

Understanding the Problem No Power, No Tripped Breaker

This strongly suggests a break in the wiring somewhere between the breaker and the heater. The break could be: A loose connection in a junction box (a likely culprit). A cut, chewed, or damaged wire. A failed component within the circuit (less common, but possible).

Wire Disappears Under Finished Floor

This is the core issue. Running wiring under a finished floor without proper conduit or protection is generally not up to code, and it makes troubleshooting very difficult.

Is Capping the Wires and Running a New Feed Acceptable?

In short, Yes, capping the existing wires in a junction box and running a new feed is often the best and safest solution IF you do it correctly and up to code.

Here's a more detailed breakdown:1. Locate and Safely De-energize



ABSOLUTELY FIRST

Turn off the breaker that feeds this circuit. Verify it's off with a non-contact voltage tester before touching any wires. Trace the existing wire as far as you can before it goes under the floor. This might help you narrow down the area where the problem lies.2.

Proper Junction Box Installation



Choose the Right Box

Use an appropriately sized junction box that is rated for electrical use. Metal or plastic is acceptable, as long as it meets local codes. The box must be accessible (not buried behind drywall).

Secure the Box

The junction box must be securely mounted to a structural element (stud, joist, etc.). It can't just be dangling.

Proper Wire Connections

Use appropriately sized wire connectors (wire nuts) rated for the wire gauge you're using. Make sure the connections are tight and secure. Pigtail the wires if needed, ensuring good contact. Wrap the junction box in electrical tape once the wires are capped off.

Cover Plate

The junction box must have a blank cover plate that is securely fastened. The cover plate must be accessible, don't bury the junction box.3.

Running the New Feed



Code Compliance is Critical

This is where proper electrical knowledge and local codes are paramount.

Wire Type and Gauge

Choose the correct wire type (e.g., NM-B, THHN/THWN) and gauge (size) for the heater's amperage and the circuit's breaker rating. A 1500W heater on a 120V circuit draws around 12.5 amps, so 14 gauge is likely sufficient for a 15 amp breaker, but 12 gauge is preferable, but

consult your local electrical codes. Use 12 gauge if on a 20 amp breaker. Wiring Methods

How you run the wire is crucial.

Conduit

If running the wire through unfinished areas (attic, basement), consider using conduit (EMT, PVC) for physical protection.

Securing the Wire

Secure the wire properly to studs or joists every few feet using appropriate staples or cable ties. Do not over-tighten staples, which can damage the wire.

Boring Holes

When passing wires through studs or joists, maintain the proper distance from the edges (typically 1 1/4 inches; check local codes). Use metal nail plates to protect the wire if it's closer than that.

Dedicated Circuit

Baseboard heaters often require a dedicated circuit. Don't overload an existing circuit.

GFCI Protection

Check local codes. GFCI protection might be required in certain locations (bathrooms, garages, unfinished basements).4.

Connecting the New Feed to the Heater

Follow the heater manufacturer's instructions carefully. Make sure all connections are tight and secure. Use the correct wire connectors.

Important Considerations and Warnings Local Codes

Electrical codes vary significantly by location. What is acceptable in one area might be a violation in another. You are responsible for complying with all local codes. If you're unsure, contact your local building department or a qualified electrician.

Permits

Depending on your area and the scope of the work, you might need an electrical permit.

Professional Help

If you are not completely comfortable and knowledgeable about electrical wiring, hire a licensed electrician. Electrical work is dangerous, and mistakes can lead to fire, shock, or even death.

Abandoning the Old Wire

After capping the old wires, ensure they are truly dead. Don't energize them again. Label the junction box clearly with a warning that the wires are abandoned.

Hidden Dangers

Be aware that there might be other hidden wiring or problems in the area under the finished floor. Exercise caution when working in that space.

In Summary

Capping the old wires in a properly installed junction box and running a new feed is a viable solution, but only if done correctly and in compliance with all local codes. If you lack the knowledge or experience, hire a licensed electrician. It's the safest and most responsible course of action. Flag for review