Okay, let's break down your observation of tray cable (TC) in an old house being gutted. You're right, it raises some interesting questions about historical wiring practices and code compliance.

Here's what we need to consider



What is Tray Cable (TC)? Tray cable is a factory-assembled multi-conductor or single-conductor assembly with a nonmetallic jacket, specifically approved for installation in cable trays. It's designed for industrial and commercial applications where cables need to be supported and managed in a structured manner. TC is designed to resist physical damage, moisture, and sunlight. It's generally more robust than NM or UF cable. TC Color Coding and Grounds

TC color codes are generally not standardized like NM cable. They often follow a custom scheme based on the manufacturer and the intended application. Orange as a ground is possible but not guaranteed. TC typically has a dedicated, insulated grounding conductor.

Was TC Ever Allowed in Residential Wiring Like NM (Romex)? Generally, no, TC is NOT intended as a direct substitute for NM (Romex) cable in typical residential branch circuit wiring. Code Articles

The NEC (National Electrical Code) dictates the types of wiring methods permitted for various applications. NM cable is specifically listed and described in Article 334, while TC is covered in Article 392. The use of TC outside of a cable tray is limited to the conditions listed in 392.10(B).

Intended Use

NM cable is designed for dry, indoor locations in residential buildings. TC is for industrial, commercial, and potentially some outdoor (with appropriate TC rating) environments.

Flexibility and Installation

NM cable is more flexible and easier to install in the confined spaces of residential walls and ceilings. TC is typically stiffer and intended for open runs in trays or supported by other means.

Why Might You Find TC in an Old House? Non-Compliant Installation

It's the most likely answer. A previous homeowner or contractor might have used TC because it was readily available, perceived as "better," or simply out of ignorance of the code requirements.

Specific Appliance Circuits

There might be very specific cases where TC was used for a dedicated circuit to a high-power appliance (e.g., a large oven, HVAC unit) if it met all applicable code requirements at the time of installation, including proper support and termination. This would be less common, and the installation would have needed to be inspected and approved.

Additions or Modifications

An addition to the house might have been done using TC if it was connected to a commercial structure or if it was misapplied.

Industrial or Commercial Origin

The house might have originally been part of a commercial or industrial facility that was later converted to residential use. In this case, the TC could have been part of the original wiring.

Points to consider

392.10(B)(1)(a) allows TC cable outside of a cable tray as long as it is continuously supported and protected against physical damage using conduit, raceways, or other means. 392.10(B)(1)(b) allows TC cable without continuous support for lengths not exceeding 6ft at the termination where the cable is protected against physical damage using conduit, raceways, or other means.

Therefore, in summary

Finding TC cable in an old house being gutted is unusual. While it's possible it was installed in a compliant manner for a specific purpose (especially if properly protected as it leaves the tray system), the most likely explanation is that it was a non-compliant installation.

Important Considerations for Gutting/Renovating


Safety First

Assume all wiring is potentially hazardous until proven otherwise.2.

Professional Assessment



Crucially, have a licensed electrician inspect the wiring before* you do any significant work. They can determine if the TC cable is safe, code-compliant (or was at the time of installation), and whether it needs to be replaced or modified.3. Code Compliance

Ensure all new wiring meets current NEC requirements.4.

Documentation: Document any unusual wiring you find (photos, notes) for the electrician.Don't assume that just because it's "old" it's grandfathered in. If the existing wiring is unsafe or doesn't meet current code, it will need to be brought up to code during the renovation.I hope this helps! Let me know if you have any other questions. Flag for review