By Eileen Harvey
In electrical engineering and industrial wiring, selecting the correct tray cable gauge is one of the most critical decisions you’ll make. The gauge size impacts everything from currentcarrying capacity (ampacity) to voltage drop and installation flexibility. A properly sized tray cable ensures reliable operation, extends the lifespan of your wiring system and meets NEC, UL and CSA standards.
In this guide, we walk through what tray cables are, the meaning of AWG sizes, a detailed tray cable size chart, key factors in selecting the right gauge, common tray cable types and their availability, compliance standards and installation tips. By the end, you’ll be able to confidently select the correct tray cable for your next industrial or commercial project.
What Are Tray Cables?
Tray cables are multiconductor cables designed to be installed in cable trays, raceways, or openair runs. They’re used for power distribution, control signals, instrumentation and communication wiring in industrial plants, commercial buildings and utility facilities.
Key features include durable outer jackets that resist sunlight, oil, moisture and mechanical damage, along with flame-retardant construction that meets UL and NEC fire safety requirements. These cables are also rated for both indoor and outdoor use, making them suitable for wet, dry or even hazardous environments.
Tray cables are versatile and come in different constructions, voltage ratings and jacket materials. But before selecting one, you must determine the correct conductor size.
Understanding Tray Cable Gauges (AWG)
The American Wire Gauge (AWG) system standardizes wire sizes in North America. In this system:
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A smaller AWG number = thicker conductor = higher current capacity
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A larger AWG number = thinner conductor = lower current capacity
For example, an 18 AWG cable can carry ~14–16 amps, and a 4 AWG cable can carry ~85–95 amps.
Gauge size matters because it directly affects ampacity, helping prevent overheating and potential fire hazards. It also influences voltage drop, ensuring that the proper voltage reaches connected equipment. In addition, conductor size impacts flexibility, since larger conductors are stiffer and more difficult to route. Finally, selecting the right gauge is important for cost efficiency, as oversizing wastes money while undersizing can compromise safety.
Factors to Consider When Choosing Tray Cable Size
While the chart is a helpful reference, sizing decisions require more context. Here’s what to consider:
Current Load Requirements: Match the cable’s ampacity to the maximum continuous current load. Also, factor in startup current surges for motors.
Voltage Drop: Long runs increase resistance, reducing delivered voltage. NEC recommends ≤3% voltage drop for branch circuits. For long distances, choose a larger conductor size.
Application Type: For control wiring, smaller gauges (16 to 18 AWG) are often used. Power circuits are typically 14 AWG and larger. For instrumentation, smaller gauges, often shielded, are used.
Environmental Conditions: Outdoor or exposed runs may require UVresistant jackets. Hazardous locations may require armored tray cables. Also note that high temperatures reduce ampacity.
Common Tray Cable Types and Their Gauge Availability
Tray cable (TC) is a general-purpose cable rated up to 600 volts and is available in a wide range of gauges from 18 AWG up to 4/0 AWG, making it suitable for a variety of power distribution and control applications. TC ER (exposed run) offers the same gauge range but includes extra mechanical protection, allowing it to be used for short open-air runs without conduit.
Instrumentation tray cable (ITC) is designed for low-voltage signal wiring, typically rated at 300 volts, and is commonly available in smaller gauges from 22 to 16 AWG. Power limited tray cable (PLTC) serves low-energy systems such as alarms and intercoms, also usually found in the 22–16 AWG range. These cable types provide flexibility in both power and signal applications while meeting specific environmental and mechanical requirements.
Compliance and Standards
Tray cables must meet specific standards for safety and performance:
NEC (National Electrical Code): Article 336 covers TC cables and Article 727 covers ITC cables. Ampacity requirements are in NEC Table 310.15(B)(16).
UL (Underwriters Laboratories): UL 1277 covers tray cable construction, testing and labeling.
CSA (Canadian Standards Association): C22.2 covers Canadian safety and performance standards.
Always verify local code requirements before installation.
Cable Tray vs. Conduit: Impact on Sizing
The method of installing tray cable has a direct impact on sizing and ampacity. When cables are run in a cable tray, they benefit from better air circulation, which improves heat dissipation and often allows the use of smaller gauge sizes compared to conduit. Cable trays also make it easier to add or remove cables, supporting future upgrades and modifications with minimal disruption.
In contrast, conduit restricts airflow and can trap heat, requiring ampacity to be derated in tightly packed runs to prevent overheating. While conduit may limit flexibility in adding or adjusting cables, it provides superior mechanical protection, shielding cables from physical damage and environmental hazards.
Quick Selection Tips
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Start with the load – Calculate ampacity requirements.
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Check run length – Increase size for long runs to avoid voltage drop.
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Consider installation – TC ER for open runs, TC for tray/conduit. You can explore TKD Cables options for a range of gauges, jacket materials and tray cable types built for industrial use.
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Verify environment – UV resistance, flame rating, temperature tolerance.
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Stay compliant – Crosscheck with NEC, UL and CSA.
Choosing the correct tray cable gauge is a balance of performance, safety and compliance. The tray cable size chart offers a solid starting point, but realworld conditions—like run length, load characteristics and environmental challenges—must be factored in. By following NEC guidelines, consulting UL and CSA listings, and considering the specific application needs, you can ensure a safe, efficient and longlasting installation.
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