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FT4 is a flame test classification defined by the Canadian Standards Association (CSA) for assessing flame resistance in electrical cables installed in vertical pathways. Specifically, it refers to the CSA Vertical Tray Flame Test, which is designed to evaluate how cable performs when exposed to a sustained flame in a vertical configuration—simulating a potential fire condition in multi-floor environments.
Where FT4 Cables Are Used
Cables that meet the FT4 flame rating are commonly used in riser applications, which include vertical shafts and conduits that connect multiple floors in commercial, institutional, and industrial buildings. Examples include:
- Elevator shafts
- Stairwells
- Cable risers
- Utility shafts
- Multi-story mechanical spaces
While FT4 cables are not suitable for air-handling ducts or plenum spaces, they do meet the flame propagation requirements outlined in the Canadian Electrical Code (CEC) for general-purpose and riser installations.
What the Test Involves
The CSA FT4 Vertical Tray Flame Test involves bundling the cable vertically on a metal tray and subjecting it to a 70,000 BTU/hr flame for 20 minutes. To pass the test, the cable must limit flame spread to no more than 1.5 meters (approximately 4.9 feet) vertically from the point of ignition.
This test simulates a fire condition in vertical conduits or risers, where fire can spread quickly upward. The flame resistance demonstrated by FT4 cables helps to limit vertical fire propagation in these scenarios, reducing structural and occupant risk.
Key Characteristics of FT4 Cables
- Moderate flame-retardant capability suitable for most vertical installations
- Accepted by Canadian code for non-plenum, multi-floor building applications
- Manufactured with various jacket types, including PVC and low-smoke variants
- Not approved for air plenums or ducts, where FT6-rated cables are required
While FT4 offers significant flame resistance, it does not meet the more stringent tunnel test performance required for FT6 (CSA) or CMP (U.S. NFPA 262) ratings. Direct comparisons between these ratings should be made cautiously, as they follow different testing methodologies.
FT4 vs. Other CSA Flame Ratings
| CSA Flame Rating | Application Environment | Flame Test Type | Typical Use Case |
|---|---|---|---|
| FT1 | Horizontal / single-conductor | Vertical flame test | Internal equipment wire, single runs |
| FT2 | Consumer appliances | 15° inclined flame test | Appliance cords and flexible cables |
| FT4 | Riser spaces, multi-floor paths | Vertical tray test | Vertical cable risers and shafts |
| FT6 | Air plenums / ductwork | Steiner tunnel test | HVAC ducts, ceiling plenum spaces |
Conclusion
FT4-rated cable provides a balance of flame resistance and cost-effectiveness, making it the standard choice for riser-rated applications in Canadian construction. By limiting vertical flame propagation, FT4 helps meet safety requirements for most multi-story installations, excluding only specialized air-handling areas that require FT6.
