What is UL 1685? Vertical-Tray Flame-Testing Standards

Undersanding Fire Propogation Rules, Smoke Release Metrics, & Industrial Cable Compliance

While standards like UL 83 and UL 44 dictate how individual electrical conductors are built, UL 1685 governs how those cables behave in a worst-case fire scenario.

UL 1685 is the definitive safety standard for Vertical-Tray Flame-Propagation and Smoke-Release Tests for Electrical and Optical-Fiber Cables. If your commercial or industrial project involves routing cables through open, vertical building shafts or overhead cable tray networks, an inspector or project engineer will likely look for a UL 1685 certification on your cable.

The Testing Essentials

A cable does not earn a UL 1685 listing through basic material analysis; it must survive a brutal, live-fire laboratory simulation. The standard is split into two primary testing methods that manufacturers use to verify safety:

• The UL 1685 Standard Protocol: Multiple cables are bundled vertically on an 8-foot steel ladder tray inside a specialized burn chamber. A massive burner exposes the bottom of the cables to approximately 70,000 BTU/hr of intense flame for a continuous 20 minutes.

• The FT4 / IEEE 1202 Protocol: A more stringent, alternative testing method frequently specified in heavy industrial layouts. The cables are spaced out on the vertical tray, and the burner is angled upward to simulate severe draft conditions, testing the absolute limit of the cable jacket’s fire resistance.

• The Pass/Fail Baseline: To pass either protocol, the flame damage cannot travel up the cable to the top of the tray (the char height must stay under approximately 4 feet 11 inches). Additionally, specialized sensors measure total smoke release to ensure the burning plastic won't blind building occupants or emergency personnel during an evacuation.

Why Engineers Specify UL 1685

A cable carrying a UL 1685 flame listing is specified across high-capacity layouts for three critical safety and legal reasons:

• Mandatory Cable Tray Compliance: Per National Electrical Code (NEC) guidelines, cables installed in industrial cable trays—such as Type TC-ER (Tray Cable) or certain sizes of Type MV-105 (Medium-Voltage Power Cable)—must carry a recognized vertical tray flame listing to ensure they won't act as a fuse that carries fire from floor to floor.

• Life-Safety Smoke Reductions: In confined commercial environments, heavy smoke is often more dangerous than the fire itself. The smoke-release testing in UL 1685 ensures that the cable jacket utilizes specialized self-extinguishing PVC, CPE, or Low-Smoke Zero-Halogen (LSZH) compounds that minimize toxic gas generation.

• Code-Approved Exposed Runs: For Type TC cables carrying the highly sought-after "ER" (Exposed Run) rating, passing a strict vertical tray fire test is a foundational manufacturing requirement that allows installers to run the cable out of the tray directly to field equipment without using rigid pipe.

How Wire America Can Help

At Wire America, we offer a professional-grade selection of industrial control, power, and medium-voltage cables that fully comply with UL 1685 and IEEE 1202 vertical flame test standards.

• Multi-Conductor Tray Lines: We stock a complete line of Type TC-ER Tray Cables (including standard THHN/PVC VNTC configurations) engineered to resist flame propagation and simplify conduit-free transitions.

• Medium-Voltage Feeders: Our Aluminum & Copper MV-105 Power Cables (sizes 1/0 & larger) feature heavy-duty, sunlight-resistant jackets that meet rigorous industrial fire protection metrics for primary power distribution.

• Cut to Length: Industrial builds require precise execution. We cut our tray and medium-voltage stock to the exact foot, ensuring you get the precise length your submittal demands without paying for unnecessary master reel waste. 

Get in Touch with Our Team

• Call us today: (833) 268-8644

• Email: sales@wireamerica.com

Wire America believes in genuine conversation. You'll always talk with real people who understand that every project requires careful product selection. We're here to ensure you feel educated, confident, and great about your final purchase. Feel free to give us a call to discuss your project! You can reach us at: 833-268-8644

⚠️ Important Disclaimer: Safety and Compliance

Wire America provides this information as a guide only. Electrical installations must strictly adhere to the National Electrical Code (NEC) and all state, local, and jurisdictional requirements, which vary widely. Always consult a licensed electrician, electrical engineer, or the local inspecting authority before purchasing material or starting any electrical project. Wire America assumes no liability for the installation, use, or interpretation of these guides.