Tray cable is a multi-conductor or multi-pair power, control, or instrumentation cable approved for installation in cable trays without additional conduit. It is the standard wiring method for industrial plants, commercial buildings, and utility installations where cable trays provide accessible, organized routing for large numbers of circuits. Choosing the right tray cable type — TC, TC-ER, VNTC, PLTC, or ITC — depends on the voltage class, environment, and NEC® article governing your installation. This guide covers every major tray cable type, their construction, ratings, and the applications where each one belongs.
What Makes a Cable "Tray Cable"?
Not every cable run in a cable tray qualifies as tray cable. The NEC® defines specific cable types that are listed and marked for tray installation under Article 336 (Type TC) and related articles. To carry the "TC" designation, a cable must pass the flame and performance tests specified in UL 1277 — including the UL Vertical Tray Flame Test (IEEE 1202 / FT4) — meet mechanical crush and impact requirements, and be marked with the appropriate type designation on its jacket.
The key distinction is that tray cable is a self-contained wiring method — the cable itself provides all the insulation, shielding, and mechanical protection needed for open tray installation. Individual THHN/THWN conductors, by contrast, generally require conduit or raceway and cannot be laid loose in a tray unless they are 1/0 AWG or larger and meet the conditions of NEC® 392.10(A), or are part of a listed tray cable assembly.
Cable trays are common in industrial and commercial environments because they allow easy cable additions, removals, and inspection without pulling through conduit. This makes tray cable the preferred wiring method for facilities that evolve over time — manufacturing plants, data centers, wastewater treatment plants, petrochemical facilities, and large commercial buildings.
Tray Cable Types and NEC® Classifications
The NEC® recognizes several cable types for tray installation. Each has a different voltage class, construction standard, and set of permitted uses. Understanding the differences prevents specification errors that lead to failed inspections or unsafe installations.
Type TC — Power and Control Tray Cable (600V)
Type TC (Tray Cable) is the general designation for 600V multi-conductor cables listed under UL 1277 and installed per NEC® Article 336. TC cable is constructed with copper conductors (14 AWG through 1000 kcmil) insulated with THHN, THWN, XHHW, or crosslinked polyethylene (XLP/XLPE), bundled together with an optional ground conductor, and jacketed in PVC, CPE (chlorinated polyethylene), or other approved materials.
Standard Type TC cable is approved for installation in cable trays, raceways, and outdoor locations where supported by messenger wire. It is not approved for direct attachment to building surfaces unless it also carries the TC-ER rating (see below). This is one of the most common specification mistakes — standard TC must stay in the tray or in conduit.
Common constructions:
| Construction | Insulation | Jacket | Typical Use |
|---|---|---|---|
| THHN-PVC (VNTC) | PVC/Nylon (THHN) | PVC | General-purpose power and control in dry/damp locations |
| XHHW-PVC | Crosslinked PE (XHHW) | PVC | Wet locations, higher temperature rating |
| EPR-CPE | Ethylene Propylene Rubber | Chlorinated PE (CPE) | Industrial environments, oil/chemical exposure, flexible installations |
| XLP-PVC | Crosslinked Polyethylene | PVC | Power distribution, direct burial with appropriate rating |
Type TC-ER — Exposed Run Tray Cable
Type TC-ER (Tray Cable – Exposed Run) meets all the requirements of standard TC plus additional crush and impact resistance tests that allow it to be installed outside of cable trays. TC-ER cable can be secured directly to building surfaces, run along structural members, and installed in open air between the cable tray and the equipment it serves — without conduit.
This is a significant advantage in industrial installations. Without TC-ER, every cable leaving the tray must transition into conduit to reach the equipment connection point. TC-ER eliminates that conduit stub-up, reducing material cost, labor time, and potential leak points in the raceway system. NEC® 336.10(7) permits TC-ER to be installed as open wiring between the tray and the utilization equipment, provided it is supported and secured per the manufacturer's instructions.
Most modern tray cable is dual-rated TC / TC-ER. When specifying new cable, always request TC-ER to maintain maximum installation flexibility.
VNTC — Vinyl-Nylon Tray Cable
VNTC is the most common construction for 600V tray cable. The name describes the insulation system: individual conductors are insulated with vinyl (PVC) with a nylon overlay — the same insulation system used in THHN/THWN building wire — then cabled together and jacketed in PVC. The result is a cost-effective, general-purpose tray cable suitable for power, lighting, and control circuits in commercial and industrial applications.
VNTC is rated 600V, 90°C dry / 75°C wet, and is available in conductor sizes from 14 AWG through 1000 kcmil with 2 to 37 or more conductors. It is commonly specified as TC-ER rated, allowing exposed run installation. VNTC is the workhorse cable for most cable tray installations where the environment does not demand the chemical resistance or flexibility of EPR-CPE construction.
Ramcorp stocks VNTC tray cable in a wide range of conductor counts and sizes, including configurations with ground conductors.
EPR-CPE — Industrial-Grade Tray Cable
EPR-CPE tray cable uses ethylene propylene rubber (EPR) insulation with a chlorinated polyethylene (CPE) jacket. This construction delivers superior performance in harsh industrial environments where VNTC falls short.
EPR insulation provides a 90°C continuous operating temperature in both dry and wet locations (compared to VNTC's 75°C wet rating), excellent flexibility even at low temperatures, and inherent resistance to ozone, sunlight, and thermal aging. The CPE jacket resists oils, chemicals, solvents, and abrasion significantly better than PVC — making EPR-CPE the preferred tray cable for petrochemical plants, refineries, pulp and paper mills, steel mills, and any facility with chemical exposure or extreme temperature cycling.
EPR-CPE costs more per foot than VNTC, but the durability advantage often makes it more economical over the life of the installation. It is typically dual-rated TC / TC-ER and available in the same conductor sizes and counts as VNTC. Ramcorp stocks EPR-CPE control cable for industrial applications.
Shielded Tray Cable (VNTC Shielded & Instrumentation TC)
Shielded tray cable adds a foil shield, braid shield, or both around individual pairs or the entire cable assembly to protect low-level analog and digital signals from electromagnetic interference (EMI) and radio frequency interference (RFI). Shielding is essential for instrumentation circuits — 4–20 mA loops, thermocouple leads, RTD circuits, and communication buses — that are particularly sensitive to electrical noise.
Shielded VNTC is available in pair configurations (twisted pairs with individual shields) and multi-conductor configurations (overall shield). Pair-shielded cable is the standard for instrumentation because each signal circuit gets its own shield, preventing crosstalk between pairs within the cable. The shield is typically aluminum/polyester foil with a tinned copper drain wire for easy termination.
For instrumentation applications below 150V, Type PLTC (Power-Limited Tray Cable) and Type ITC (Instrumentation Tray Cable) are the NEC®-recognized designations. These are covered under Articles 725 and 727, respectively, and have thinner insulation and smaller conductor sizes (typically 22–16 AWG) appropriate for low-power signal circuits. Ramcorp carries shielded VNTC tray cable and VNTC paired tray cable for instrumentation and control applications.
Tray Cable Type Comparison
| Specification | VNTC (THHN-PVC) | EPR-CPE | XHHW-PVC | Shielded VNTC |
|---|---|---|---|---|
| Voltage Rating | 600V | 600V | 600V | 600V (or 300V instrumentation) |
| Temp Rating (Dry) | 90°C | 90°C | 90°C | 90°C |
| Temp Rating (Wet) | 75°C | 90°C | 90°C | 75°C |
| Insulation | PVC/Nylon (THHN) | EPR | Crosslinked PE | PVC/Nylon + foil shield |
| Jacket | PVC | CPE | PVC | PVC |
| Oil Resistance | Limited | Excellent | Good | Limited |
| Chemical Resistance | Moderate | Excellent | Good | Moderate |
| Flexibility | Moderate | Excellent | Moderate | Moderate |
| Sunlight Resistance | With appropriate jacket | Excellent | Good | With appropriate jacket |
| EMI Shielding | None | None | None | Foil and/or braid |
| TC-ER Available | Yes | Yes | Yes | Yes |
| Relative Cost | $ (baseline) | $$$ (50–80% more) | $$ (20–40% more) | $$ (varies by shield type) |
| Best For | General commercial/industrial | Harsh chemical/industrial environments | Wet locations, moderate chemical exposure | Instrumentation, 4–20 mA, signal circuits |
Conductor Sizes and Configurations
Tray cable is available in a wide range of conductor sizes and counts to match virtually any power, control, or instrumentation circuit requirement.
Power circuits typically use 2–4 conductors in sizes from 14 AWG through 1000 kcmil, with or without a ground conductor. A 3-conductor with ground configuration (e.g., 10/3 with ground) is the most common for three-phase motor feeds and branch circuits. Larger sizes — 2/0, 4/0, 500 kcmil and above — are used for feeder circuits and high-amperage motor loads.
Control circuits use 2–37 or more conductors in smaller gauge sizes, typically 14–10 AWG. These multi-conductor cables carry start/stop signals, interlock circuits, and relay control wiring between PLCs, motor control centers (MCCs), and field devices. The higher conductor counts reduce the number of individual cables needed in the tray, simplifying installation and cable management.
Instrumentation circuits use paired or triaded conductors in 16–22 AWG with individual pair shields. A typical instrumentation tray cable might contain 1 to 24 individually shielded pairs, each carrying a 4–20 mA analog signal or thermocouple extension circuit.
NEC® Requirements for Tray Cable Installation
Cable tray installations are governed primarily by NEC® Article 392 (Cable Trays) and Article 336 (Type TC Cable). Key requirements that affect cable selection include:
Conductor size minimums: NEC® 392.10 requires a minimum conductor size of 14 AWG for power and lighting circuits in cable trays. For control and signal circuits, smaller sizes are permitted when using PLTC or ITC cable types.
Cable tray fill: NEC® 392.22 limits the number and size of cables permitted in a tray based on tray width, cable type, and voltage class. Single-conductor cables 1/0 AWG and larger have different fill rules than multi-conductor cables. Exceeding fill limits causes heat buildup and requires ampacity derating.
Ampacity derating: When more than a certain number of current-carrying conductors share a cable tray, their ampacity must be derated per NEC® Table 392.80(A)(2). This is especially important for power tray cable — a 12 AWG conductor rated at 30A in free air may need to be derated to 21A or less in a fully loaded tray.
Fire stops: Cable trays that penetrate fire-rated walls and floors must be fire-stopped with listed materials per NEC® 300.21. The fire-stop method must be compatible with the cable types and tray construction.
Grounding: Cable trays used as equipment grounding conductors must be bonded per NEC® 392.60. Metallic cable trays are commonly used as the equipment grounding path, but the tray sections must be bonded with listed fittings — not just set in place. Alternatively, tray cables with an integral ground conductor provide a dedicated grounding path independent of the tray.
Tray Cable Applications by Industry
Manufacturing and Industrial Plants
Manufacturing facilities are the primary market for tray cable. Cable trays run throughout the plant, distributing power to motor control centers, carrying control wiring between PLCs and field devices, and routing instrumentation signals from sensors to control rooms. VNTC is the standard choice for clean manufacturing environments, while EPR-CPE is specified where oil, coolant, or chemical exposure is present — such as metalworking, plastics molding, and chemical processing.
Oil, Gas, and Petrochemical
Petrochemical facilities demand the toughest cable construction. EPR-CPE tray cable with TC-ER rating is the standard because it resists hydrocarbon exposure, handles wide temperature swings, and meets the physical abuse requirements of heavy industrial environments. Shielded instrumentation tray cable carries the analog signals from field transmitters, flow meters, and pressure sensors that keep process control systems running. In classified (hazardous) locations, additional requirements under NEC® Articles 500–505 may apply.
Water and Wastewater Treatment
Treatment plants use tray cable extensively for pump motor feeds, blower controls, chemical dosing systems, and SCADA instrumentation. The moist, chemically aggressive atmosphere in treatment facilities makes EPR-CPE or XHHW construction preferable to standard VNTC. Shielded paired cable handles the 4–20 mA signals from pH sensors, flow meters, and level transmitters.
Power Generation and Utilities
Power plants — whether natural gas, nuclear, or renewable — rely on miles of tray cable for control circuits, auxiliary power distribution, and instrumentation. Nuclear plants have additional cable requirements under IEEE 383 (flame testing) and NRC regulations. Utility substations use tray cable for control wiring between protective relays, breakers, and SCADA systems.
Data Centers
Modern data centers use cable trays for power distribution to PDUs and RPPs. Tray cable (typically VNTC or XHHW construction) carries 208V and 480V power circuits, while separate trays handle low-voltage network and fiber cabling. The TC-ER rating allows direct connection from tray to equipment without conduit transitions.
Commercial Buildings
Large commercial buildings — hospitals, universities, airports — use cable trays in mechanical rooms, above ceilings, and in service corridors. Tray cable simplifies installation of HVAC control wiring, lighting circuits, fire alarm feeders, and building automation system (BAS) cabling.
Quick Selection Guide
- Determine the voltage class — Power and control circuits (up to 600V) use Type TC cable. Low-voltage instrumentation (under 150V) can use PLTC or ITC. Choose the cable type that matches your circuit voltage.
- Assess the environment — Clean, dry, indoor? VNTC is the cost-effective standard. Oil, chemical, or outdoor exposure? Specify EPR-CPE or XHHW construction. Wet locations require a 90°C wet rating (EPR-CPE or XHHW).
- Check if you need TC-ER — If the cable will leave the tray and run exposed to the equipment connection point, you need TC-ER rated cable. For new installations, always specify TC-ER to maintain flexibility.
- Determine shielding needs — Analog instrumentation signals (4–20 mA, thermocouples, RTDs) require individually shielded pairs. Power and discrete control circuits typically do not need shielding unless they run adjacent to VFDs or other high-EMI sources.
- Size the conductors — Select conductor gauge based on circuit ampacity (with tray derating applied), voltage drop over the run length, and NEC® minimums. For motor circuits, size per NEC® 430 requirements.
- Count the conductors — Multi-conductor tray cables reduce tray fill and simplify installation. A single 12-conductor control cable takes less space than six individual 2-conductor cables carrying the same circuits.
- Specify the ground — For equipment grounding, choose cable with an integral ground conductor (marked "with ground" or "W/G") rather than relying solely on the cable tray as the grounding path.
Tray Cable vs. MC Cable vs. Conduit and Wire
Three wiring methods dominate commercial and industrial power distribution. Each has cost, code, and practical trade-offs.
| Factor | Tray Cable (TC / TC-ER) | MC Cable (Metal Clad) | Conduit + THHN |
|---|---|---|---|
| NEC® Article | 336 (TC), 392 (Trays) | 330 | Various (342, 344, 348, 350, etc.) |
| Armor/Raceway | None (self-contained) | Interlocked aluminum or steel armor | EMT, rigid, IMC, or flexible conduit |
| Installation Speed | Fast — lay in tray | Fast — surface mount, no conduit | Slowest — requires conduit installation first |
| Material Cost | Low to moderate | Moderate to high | Low cable + moderate conduit/fittings |
| Labor Cost | Low | Low to moderate | Highest |
| Flexibility for Changes | Excellent — add/remove cables from tray | Moderate — individual runs | Limited — new conduit for new circuits |
| Physical Protection | Tray provides support; jacket provides protection | Armor provides crush/impact protection | Conduit provides maximum physical protection |
| Best For | Industrial plants, data centers, large commercial | Commercial retrofits, exposed runs without trays | Residential, small commercial, hazardous locations |
In many industrial facilities, all three wiring methods coexist — tray cable in the main runs, MC cable for branch circuits to individual equipment, and conduit in hazardous locations or where physical damage protection is required.
Frequently Asked Questions
What is the difference between TC and TC-ER tray cable?
Standard TC cable is approved only for installation inside cable trays, raceways, and messenger-supported outdoor runs. TC-ER (Exposed Run) cable passes additional crush and impact tests that allow it to be installed outside of cable trays — secured directly to building surfaces or run in open air between the tray and the equipment. For new installations, always specify TC-ER rated cable to avoid having to transition to conduit at every equipment connection.
Can I use tray cable in conduit?
Yes. Type TC cable is permitted in raceways (conduit) per NEC® 336.10. However, it is generally not cost-effective to run multi-conductor tray cable in conduit — the cable is designed to be its own wiring method in a cable tray. If the installation requires conduit, individual THHN/THWN conductors are typically less expensive and easier to pull.
When should I choose EPR-CPE over VNTC?
Specify EPR-CPE when the cable will be exposed to oils, chemicals, solvents, or hydraulic fluids; when you need a 90°C wet location rating; when the cable must remain flexible in cold temperatures (below 0°C); or when the environment subjects the cable to heavy physical abuse. VNTC is the better choice for clean, dry-to-damp environments where cost is a primary concern.
Do I need shielded tray cable for VFD (variable frequency drive) circuits?
The VFD output cable (from drive to motor) should typically be shielded or use VFD-rated cable to contain the high-frequency noise generated by the drive's pulse-width modulation output. However, the control and instrumentation cables running near VFDs also benefit from shielding if they carry sensitive analog signals. For discrete control circuits (24V on/off), standard unshielded tray cable is usually adequate if proper separation distances are maintained per VFD manufacturer recommendations.
What is the maximum conductor count available in tray cable?
Standard tray cable is available with up to 37 power/control conductors or up to 24+ individually shielded pairs for instrumentation. Higher conductor counts are available as custom orders. For most applications, 12-conductor and 7-conductor configurations are the most commonly stocked sizes after the standard 2-, 3-, and 4-conductor power configurations.
Can tray cable be direct buried?
Only if the cable is specifically listed and marked for direct burial. Some tray cable constructions — particularly those with moisture-resistant XHHW or EPR insulation and appropriate jackets — carry a dual TC / direct burial rating. Always verify the cable's listing markings before specifying it for underground installation.
What size cable tray do I need?
Cable tray sizing depends on the number and diameter of the cables, the fill rules in NEC® 392.22, and any future capacity you want to reserve. As a rule of thumb, most engineers specify trays at 40–60% fill to allow for future cable additions. Tray width is selected so that the total cross-sectional area of all cables does not exceed the fill limits in the NEC® tables. Your cable tray manufacturer or distributor can provide fill calculation tools.
Related Resources
- How to Read a Cable Print Legend: Markings, Codes & What They Mean
- UL Listings for Wire & Cable: What to Look For
- How to Choose the Right Cable for Your Project
- Direct Burial Cable: Types, Depth Requirements & Selection
- Plenum vs. Riser Cable: CMP, CMR, CL2P & CL3P Ratings Explained
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