Flammability Tests and Ratings
UL Flammability Test
| Test | BTU/hr – Locations | |
|---|---|---|
| UL 1581 (VW-1) | Bunsen Burner | Residential & Non-Residential in Conduit |
| UL 1581 (Vertical Tray) | 70,000 (IEEE 383) | General Purpose |
| UL 1666 (Vertical Chamber) | 527,500 | Riser and General Purpose |
| UL 910 (Steiner Tunnel) | 320,000 | Plenum, Riser, General Purpose |
UL VW-1 Vertical Wire Flame Test
The purpose of the UL VW-1 Vertical Wire Flame Test is to screen out flammable wires. The ignition source is small (under 1 kW) and is applied for only 75 seconds.
In the UL VW-1 Flame Test, a tirrill burner (similar to a Bunsen burner) is used as the ignition source. The wire sample is mounted and the flame is applied for 15 seconds and then removed. The flame is then reapplied, either after 15 seconds or when the sample ceases to flame (whichever is longer), for a total of five 15-second applications. After the above procedure is completed, a wire sample that passes this test must not burn for more than one minute and must not burn more than 25% of the Kraft indicator flag. In addition, the surgical cotton at the base of the burner must not be ignited.
IEEE 383 Vertical Flame Test
The Institute of Electrical and Electronic Engineers (IEEE) has established IEEE-383, “IEEE Standard for Type Test of Class IE Electric Cables, Field Splices and Connections for Nuclear Generation Stations”. Although originally intended for cables essential for emergency operations in nuclear power plants, this test procedure is used for other non-nuclear installations.
In the IEEE-383 fire test cables are supported by a one-foot wide vertical rack eight feet high. The cables are positioned in the center six inches of the rack, spaced one-half cable diameter apart. The rack is centered in an eight-foot cube enclosure recommended by Underwriters Laboratories, a ten-inch ribbon burner fuel with an air-propane mixture ignites the cable with a 21 kW (7,000 Btu/hr) flame. The burner is positioned 2 feet above the floor and 9 to 12 inches of cable are exposed to the direct flames for 20 minutes. Cables on which flame extends above the top of the 8-foot rack fail this test.
NELPIA (ANI) test is a (21,000 BTU/hr) vertical flame test corner configuration test.
Vertical-Tray Flame Test (210,000 BTU) ICEA T-29-520
Similar to 70,000 BTU per hour test but heat source increased to 210,000 BTU per hour.
Factory Mutual Cable Fire Propagation Test
A unique test standard whereby a Fire Propagation Index (FPI) is determined based upon a combination heat release and ignition test. The FPI is used to determine a 1, 2, or 3 Group rating. The lower Group ratings are the better performing cables.
This test chamber is an eight by four simulated shaft, twelve feet high between the source of ignition and the floor above. A very large propane burner, 145 kW (495,000 BTU/hr) is ignited for a period of 30 minutes. Flames must not extend above the 12-foot mark if the cable is to be UL Classified for this duty.
UL-910 Plenum Test
A plenum is defined as any space used as part of an air-handling system. This includes heating/air-conditioning ducts and air returns, which frequently include the space between suspended ceilings and the floor above in modern office buildings. The National Electric Code (NEC) requires that exposed cables (those not in conduit) in plenums be listed as having adequate fire-resistant and low-smoke producing characteristics…”
A “Standard For Test Method for Fire and Smoke Characteristics of Cables Used in Air-Handling Spaces”, was developed by Underwriters Laboratories (UL) to classify cables for this NEC requirement. This test is performed in a 25 foot Stein – Tunnel test furnace (also specified in ASTM E-84 test for building materials). Designed to match the rigors of the application, this test is quite demanding.
In the UL-910 test, a single layer of 24-foot lengths of cable is supported by a one-foot wide cable rack, which is filled with cables. The cables are ignited by an 88 kW (300,000 BTU/hr) methane flame. Flame spread is aided by a 240 ft/minute draft. During the 20 minute test, the flame spread is observed through small windows spaced one foot apart. Smoke is measured by a photocell installed in the exhaust duct.
To qualify, cables must have a flame spread of fewer than 5 feet beyond the end of the 4-1/2 foot ignition flame, a peak optical density of 0.5 maximum (33% light transmission) and a maximum average optical density of 0.15 (70% light transmission).