By Eileen Harvey
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, outline installation best practices and give 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.
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.
Tray cables usually carry a “TC” (tray cable) or “TC-ER” (exposed run) rating, providing flexibility for different installation environmentsꟷincluding cable trays, raceways and sometimes open runs. Their robust jacketing often makes them suitable for moderately demanding settings, when installed according to code.
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.
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.
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. For longer open runs or high-risk locations, additional protection (e.g., conduit) may still be necessary.
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.
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. 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.
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.
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.
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.
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.
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.
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