By Eileen Harvey
Key Takeaways
- Tray cables are designed to run openly in listed cable trays under NEC Articles 336 and 392, so they generally do not need conduit when installed in a tray.
- TC-ER cables can leave the tray for exposed runs of up to 6 feet to connected equipment without conduit, in industrial establishments and when secured and protected from damage.
- Conduit is typically required underground (unless the cable is rated for direct burial), in areas with heavy mechanical risk, in many hazardous locations and wherever local codes or the AHJ require it.
- Conduit adds protection but also cost, labor, heat buildup and ampacity derating, so it should be used where the added protection is justified.
- Always confirm requirements against the NEC, UL/CSA listings, manufacturer instructions, local codes and the AHJ.
When planning a modern electrical system for industry, utilities or commercial spaces, the question “Do tray cables need to be in conduit?” naturally comes up. This is a crucial consideration for both safety and code compliance—and impacts project budgets, installation methods and long-term cable access. This article demystifies when tray cables do and don’t require conduit, outlines installation best practices and gives you actionable tips for every application.
Tray Cables vs. Conduit—What’s the Debate?
Tray cables (TC, TC-ER, and similar types) are specially designed for use in cable tray systems, which support multiple runs of cable across industrial and commercial buildings. Conduit, on the other hand, is a rigid or flexible tube that provides additional mechanical protection and environmental isolation for conductors. Understanding when tray cables require conduit, and when they don’t, is critical for both code compliance and efficient cable installation. To answer that question, it helps to start with what each option is designed to do.
Understanding Tray Cables
Tray cables are multi-conductor cables manufactured and tested to withstand industrial environments. They’re commonly used in power distribution, control circuits, instrumentation and data/communication lines. For a full overview of types and standards, see the ultimate guide to tray cables.
Tray cables usually carry a “TC” (tray cable) or “TC-ER” (exposed run) rating, providing flexibility for different installation environments—including cable trays, raceways and sometimes open runs. Their robust jacketing often makes them suitable for moderately demanding settings, when installed according to code. Insulation matters too; compare the options in PVC vs. XLPE insulation for tray cables.
For NEC-compliant options, you can explore the TKD tray cable collection, which includes TC-ER and TC-ER-JP cables. They are suitable for a wide range of installations, including industrial and select residential use. Learn more about where they are permitted in our article on using tray cables in residential wiring.
How Conduit Is Used in Electrical Installations
Conduit is any enclosed channel—rigid or flexible, metallic or nonmetallic—used to route and protect cables and wires in buildings. It shields cables from mechanical damage, rodents and vibration, while also guarding against moisture, chemicals, UV and other environmental factors. In addition to physical and environmental protection, conduit is often required by electrical codes in certain environments or for specific cable types. So where does each option fit in a real installation?
Tray Cable Installation Methods
Cable Tray Systems
The primary use case for tray cables is found in the name: cable trays. Per NEC Article 392 and Article 336, tray cables can run openly in listed cable trays, well supported and protected from excessive damage. Cable trays allow easy access for maintenance, which is one of their greatest advantages over conduit.
Exposed Runs and Alternate Methods
TC-ER-rated cables can be installed in exposed runs outside the cable tray, up to 6 feet between the cable tray and connected equipment, and without conduit—provided that the cable is secured and protected from mechanical damage, per code. This allowance applies in industrial establishments where only qualified persons service the installation. For longer open runs or high-risk locations, additional protection (e.g., conduit) may still be necessary. Which raises the key question: when exactly is conduit required?
When Is Conduit Required for Tray Cables?
Conduit may be required for tray cables in a variety of situations where added protection or compliance is necessary. In environments with forklifts, vehicles or heavy equipment, conduit helps safeguard tray cables from impacts, crushing and abrasion. Outdoor and underground applications also often call for conduit. Standard tray cables must be placed in conduit when run underground unless they are specifically marked for direct burial, and outdoors conduit can provide additional defense against UV exposure and extreme weather.
In hazardous or classified locations such as chemical plants, explosive atmospheres or damp environments, conduit is frequently mandated to ensure maximum safety. Local building codes, insurance requirements or directives from the Authority Having Jurisdiction (AHJ) can also require conduit even in cases where national standards do not. In fact, if a tray cable is not rated for direct burial, the National Electrical Code explicitly requires it to be installed in conduit or duct when placed underground. When conduit is required, it brings both benefits and trade-offs.
Tray Cables in Conduit: Advantages and Considerations
Running tray cables in conduit provides multiple benefits, including mechanical protection against impact, rodents and vibration, as well as added resistance to chemicals and water in corrosive or wet environments. Conduit also enhances security by making accidental or intentional tampering more difficult.
At the same time, there are important considerations to keep in mind. Bundling multiple cables inside conduit can create heat buildup, and per NEC Table 310.15(C)(1), ampacity must be derated when multiple conductors share the same conduit. Our tray cable size chart can help you choose the right gauge with derating in mind. Conduit fill must also be calculated carefully, as overfilling is a code violation. Finally, while conduit offers valuable protection, it requires more time, labor and materials to install compared to cable trays, which can add to overall project costs. Here’s how the two approaches compare at a glance.
Tray Cable vs. Conduit: Cost, Installation and Maintenance
Cable trays are generally more cost-effective and flexible for long cable runs, especially in industrial and data center environments:
| Feature | Cable Tray | Conduit |
|---|---|---|
| Cost | Lower for large systems | Higher due to labor/material |
| Ease of Installation | Fast, scalable | More involved, less flexible |
| Maintenance | Easy cable access | Harder to remove/replace |
| Physical Protection | Moderate | Excellent |
Conduit is best when maximum protection is needed, but otherwise, cable trays exploit tray cables’ inherent strengths. Whichever you choose, the installation must meet code.
Code and Standards Compliance
There are two key sections in the National Electrical Code (NEC) that provide particularly relevant compliance information. Article 336 covers permitted uses and installation rules for tray cables. Article 392 covers cable tray construction, installation and allowable cable types.
Always follow UL, CSA and manufacturer installation guidelines, and assess idiosyncratic local code modifications or AHJ preferences. Still have questions? Here are the ones we hear most often.
Frequently Asked Questions (FAQs)
Q1: Can all tray cables be run without conduit?
A: Only if installed in a listed cable tray or in exposed runs up to 6 feet using TC-ER cable outside the tray, and only if not subject to mechanical damage or code exceptions. The 6-foot exposed-run allowance applies in industrial establishments where only qualified persons service the installation.
Q2: What are TC-ER and MC cables?
A: TC-ER is “tray cable, exposed run,” suitable for short runs outside the tray; MC is “metal-clad cable,” which sometimes substitutes for tray cable and typically offers higher mechanical protection.
Q3: When should I use conduit even if not required by code?
A: Whenever there’s a risk of mechanical, chemical or water damage; in highly sensitive areas; or when extra security is needed for critical circuits.
Q4: What is the difference between TC and TC-ER tray cable?
A: Standard TC cable is designed to run in cable trays, raceways and other approved supports. TC-ER cable has passed additional crush and impact testing, which allows it to leave the tray for exposed runs to connected equipment without conduit, under the conditions set by the NEC.
Q5: Can tray cable be buried directly in the ground?
A: Only if it is specifically marked for direct burial. Tray cable without a direct-burial rating must be installed in conduit or duct when run underground.
Conclusion
Tray cables are fundamentally designed for use in cable trays rather than conduit. However, conduit becomes necessary when cables are underground and not direct-burial rated, in areas of high mechanical threat or when extra environmental protection is justified. Before finalizing your cable installation plans, always consult the NEC, UL/CSA listings, manufacturer instructions, local codes and the AHJ.
Explore L-com’s range of TKD tray cables, with same-day shipping on all qualified, in-stock, online orders received Monday through Friday before 5 p.m. EST.