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UL 1666 Riser Cables Fire Test

UL 1666 riser cable fire test is a fire test for determining values of flame propagation height for electrical and optical-fiber cables that are for installation vertically in shafts or in vertical runs that penetrate one or more floors. The purpose of this test is to determine whether the flame propagation characteristics of these ″riser″ cables are in accordance with the National Electrical Code. UL 1666 riser cable fire test does not investigate the toxicity or corrosivity of the products of combustion or decomposition. This test does not cover the construction requirements for any cable or the electrical, optical, and other performance requirements for any cable.

The test chamber is to be as shown in Figure 4.1. The test chamber, all equipment, and the cable specimens are to be protected from the wind and other conditions of weather that could affect the test results. The walls of the structure are to be of standard concrete masonry nominally 8 in (203 mm) thick. Fire Test Chamber for UL 1666
The first and second floors shall be constructed of reinforced normal-weight concrete nominally 5- 8 in (127һ203 mm) thick. The roof shall be constructed of a suitable building construction capable of providing a tight seal with the walls of the structure. A slot measuring 1 ft by 2 ft (305 mm by 610 mm) is to be located in the first floor, and an identical slot is to be located directly above in the second floor.
As shown in Figure 4.1, each slot is to be 8 in (203 mm) from the back wall of the room and 4 in (102 mm) from the side wall of the room. The slots are to be oriented adjacent to either side wall of the room based on installation and position of the fire test chamber. Windows are to be positioned as needed for observation.
Figure 4.1 Fire Test Chamber for UL 1666
The test chamber is to contain steel access doors located on the first and second floors as shown in Figure 4.1 or positioned in any of the other walls. Positioning the second floor door or an additional access hatch in the wall opposite the slot is advantageous as this allows for ease of installation of the cable specimens and positioning of second floor slot thermocouples.
The size of each access is not specified. The edges of the door frames are to use an inorganic gasketing material to ensure a tight fit of each door when closed to prevent excessive drafts in the chamber.
The burner is to consist of 1/2-in steel pipe with a 1/2-in pipe elbow, plus a steel burner diffusion plate as shown in Figure 4.2. The plate is to be located as shown in Figure 4.3. An electronic-spark igniter is to be positioned adjacent to the outlet of the gas-piping outlet for ignition of the pilot flame.Burner Apparatus for UL 1666
Figure 4.2 Burner Diffusion Plate
A propane-gas flowmeter is to be installed in the piping feeding the burner for measuring the flow rate of gas during the test. The flowmeter is to be capable of measuring a gas flow rate of 222 SCFH (standard cubic feet per hour) (1743 cm3/s). Measurements are to be accurate within 3 percent.
The burner is to consist of 1/2-in steel pipe with a 1/2-in pipe elbow, plus a steel burner diffusion plate as shown in Figure 4.2. The plate is to be located as shown in Figure 4.3. An electronic-spark igniter is to be positioned adjacent to the outlet of the gas-piping outlet for ignition of the pilot flame.
Figure 4.3 Location of Ignition Burner Relative to Floor Slot and Cables
An electric blower fan capable of providing an air velocity across the burner outlet as specified in 8.3 is to be positioned outside the chamber perpendicular to the centerline of the burner as shown in Figure 4.1. Burner Fan for UL 1666
A slot that is 6 in wide by 4 in high (152 mm by 102 mm) is to be provided in the wall of the test chamber at the first floor level to enable the fan to move air across the burner.
The gas supplied to the burner is to be CP-grade propane having a nominal heating value of 2500 Btu (thermochemical) per cubic foot [93.0 MJ/m3 or 22.2 kilocalories (thermochemical) per cubic meter].Gas Supplied: Propane
A steel exhaust duct is to be positioned in the center of the roof of the fire test chamber as shown in Figure 4.1. An exhaust blower is to be connected to the exhaust duct. The blower is to have the capacity to maintain the required air velocity specified in 8.2 throughout the duration of the test.Exhaust Blower and Duct
Eight 28 AWG Type K thermocouples with an inconel sheath are to be located in the slot in the second floor, and one thermocouple is to be located in the first floor slot, as shown in Figure 4.4.Temperature and Flow Measurement Instrumentation
One 28 AWG Type K thermocouple with an inconel sheath is to be located at the centerpoint of the first floor chamber ceiling and is to extend downward 1 +1/16 in (25.4 +1.6 mm) perpendicular to the ceiling. This thermocouple is used to determine the test chamber temperature prior to conducting a test.
A bi-directional air-velocity probe is to be located at the horizontal and vertical center (]:[) of the first floor slot as shown in Figure 4.4. The velocity probe for flow measurements is to be connected to an electronic pressure gauge to obtain diferential pressure.
A digital data acquisition system shall be used to collect and record the air inlet slot velocity and second floor slot thermocouple temperature at intervals of 5 seconds or less.Data Acquisition Equipment
Compliance with fire safety codes is crucial for any building project, and riser cables are no exception. The UL 1666 riser cable fire test is an industry-standard test that evaluates the ability of riser cables to resist flame propagation. This test determines whether the cable can be safely installed in a building’s vertical shafts or “risers,” which are key pathways for the transmission of fire and smoke during a fire event. The UL 1666 test is designed to ensure that cables meet strict safety standards and can help prevent the spread of fire through buildings.

The UL 1666 riser cable fire test is important because it ensures that riser cables installed in buildings meet the required fire-resistance capabilities. Cables that have passed this test can prevent or minimize the spread of fire through the vertical shafts or risers of a building, which is crucial for the safety of its occupants. Compliance with industry regulations is also necessary, and certification under UL 1666 provides assurance that the cables meet the minimum performance requirements. Building owners and managers should prioritize ensuring that their riser cables are up to code with UL 1666 certification to guarantee a safe and secure environment for their tenants.
IEEE 383 vertical flame test is conducted on cables that are attached to a vertical metal ladder tray. The source of combustion is a 70,000BTU ribbon burner flame source. The flame is applied for 20 minutes. IEEE 383
The rating requires the cable to self-extinguish before reaching the top of the tray. This test is very similar to the UL 1581-1160 vertical flame test and the CSA FT-4 vertical flame test.
IEEE 1202 vertical flame test is conducted on cables that are attached to a vertical metal ladder tray. The source of combustion is a 70,000BTU ribbon burner flame source. The IEEE 1202 test has its burner mounted at 20° from the horizontal with burner ports facing up. IEEE 1202
The flame is applied for 20 minutes. At the end of the 20 minute period, the burner flame shall be extinguished and the cable fire (if any) allowed to self-extinguish. The cable passes if the length of damage (charring or other affected portion) does not exceed 1.5meters (4.9ft). This test is almost the same as the CSA FT-4 Flame Test.
MSHA horizontal flame test (per U.S. Code of Federal Regulations 30 CFR Part 7.407) is required by MSHA (Mine Safety and Health Administration) to assure adequate fire resistance for cables used in the mining industry. The cable conductors are connected to a current source to raise the conductor temperature to 400 Deg F (204.4 Deg C). MSHA
The approximately 3000BTU flame source is applied to the cable for 60seconds. The flame source and the current is then removed. The cable passes if the burning does not exceed 4 minutes and the length of the burned (charred) area does not exceed 6 inches. The CSA FT-5 flame test is quite similar to the MSHA flame test.
NFPA 262 Standard Method of Test for Flame Travel and Smoke of Wires and Cables for Use in Air-Handling Spaces (Formerly UL 910) is a plenum cable test with a 300,000BTU flame source in a 25 foot tunnel chamber for 20minutes. To pass, a cable must have a flame spread of less than 5 feet with optical (smoke) density of 0.15 and maximum value of 0.50. NFPA 262
UL VW1 (UL Standard 1581-1080) vertical-wire flame test which is a small scale test conducted on a single length of wire. A 1700BTU Tirrill burner flame source (like a Bunsen burner) is applied to a vertically clamped sample at a 20° angle so that the inner flame makes contact with the wire’s surface. Below the sample is surgical cotton and near the top of the sample is a paper indicator flag. UL VW1
The flame is applied for 5 ~ 15second intervals, each time after the sample stops burning. To pass the test, the sample cannot burn longer than 60seconds after any flame application, or less than 25% of the paper indicator flag burns, or the cotton cannot ignite. This test is very similar to the CSA FT-1 flame test.
UL vertical tray flame test (UL Standard 1581-1160) is a large scale flame test in which cables are fastened to a 8 foot tall vertical metal ladder tray that is 1 foot wide. A 70,000BTU ribbon burner source is horizontally applied to vertically attached cables. In order to pass the test, the cable must self-extinguish before reaching to top of the tray. This test is similar to the CSA FT-4 Vertical Flame Test. UL Vertical Tray Flame Test
UL 1685 vertical tray test evaluates flame spread and smoke generation from wire and cable exposed to a flame. The test is essentially the same as the UL 1581-1160 Vertical Flame Test with the addition of smoke requirements. The 70,000BTU flame source is mounted at a 20° angle from the horizontal and applied to cables on a 8foot metal ladder tray for 20minutes. UL 1685 Vertical Tray Test
The cables pass the test if the cable char height is less than 8 feet, the total smoke released is 95m2 or less, and the peak smoke release rate is 0.25m2 /sec. This test determines flame propagation and smoke characteristics of these cables to qualify for a limited smoke marking.
UL 1666 riser flame test is required where cables are used in vertical runs in a shaft that may penetrate more than one floor. The tested cables are fastened vertically in a three story test chamber and a 527,500BTU flame source is applied for 30 minutes. To pass the test, the cables must have a maximum flame height of 12 feet and cable temperature must not exceed 850 Deg F. UL 1666 Riser Flame Test
The European Electrical Committee categorized the fire performance of the cables into three classes, namely IEC60332-1, IEC60332-2 & IEC60332-3. IEC Flame Retardant Grade
IEC 60332-1 and IEC 60332-2 are used to assess the flame propagation characteristics of a single wire.
IEC 60332-3 is used to assess the flame propagation characteristics of bundled cables. Comparatively speaking, IEC 60332-3 for bundled cables is more demanding than IEC60332-1 for single wires.
IEC 60332-1/BS 4066-1(Flame Test On Single VerticalInsulated Wires/Cables)
IEC 60332-1 BS 4066-1(Flame Test On Single VerticalInsulated WiresCables)
This test details a method of test for the assessment of the flame propagation characteristics of a single wire or cable. In this test, a 60cm cable sample is fixed vertically inside a metallic box and a 175mm long flame is applied at 45C from a gas burner placed at 450mm from the top at the upper portion.
The specimen is deemed to have passed this test, of after burning has ceased, the charred or affected position does not reach within 50mm of the lower edge of the top clamp which is equivalent to 425mm above the point of flame application. The test method is not suitable for the testing of some small wires due to the melting of the conductors during the time of application of the flame.
IEC 60332-3/BS 4066-3(Flame Test On Bunched Wires/Cables)
IEC 60332-3 BS 4066-3(Flame Test On Bunched WiresCables)
IEC60332-3 describes a method of type approval testing to define the ability of bunched cables to resist fire propagation. In this test, a cable specimen, consisting of number of 3.5m lengths of cables are fixed to a vertical ladder tray where they are applied with a flame from a gas burner for a specified times under controlled air flow.
Four categories (A, B, C & D) are defined and distinguished by test duration and the volume of non metallic material of the sample under test. The cable specimen is deemed to have met the requirements of the standard if, after burning has ceased, the extent of charred or affected portion does not reach a height exceeding 2.5m above the bottom edge of the burner.
If a cable can pass a specified UL fire standard, an UL performance verification mark can be applied onto the cable jacket, illustrating both the UL class and the number. There are four primary fire testing standards as follows: UL Fire standard
Plenum rated cables meet the NFPA -262 standard (formerly known as UL910) which provides the most stringent requirement of all the tests. Cable samples on a horizontal tray in a tunnel type of chamber are burned at 87.9KW (300000 BTU/Hr) for 20 minutes. To qualify for a plenum rating, the cables must have the flame spread of less than 5 feet or 1.5 meters, with a smoke density during the test of (a) 0.5 peak; and 0.15 maximum averages. Plenum Flame Test|Steiner Tunnel Test
The cable is usually installed in air ventilation duct and air return widely used in Canada and USA. The fire retardancy properties of CMP cable is much better than LSOH cable complying with IEC 60332-1 and IEC 60332-3.
Riser rated cables meets UL 1666. Cable samples on a vertical shaft are burned at 154.5KW (527500 BTU/Hr) for 30 minutes. To qualify for a riser rating, the cables must have the flame spread of less than 12 feet beyond the ignition point. This test does not look at the smoke density or toxicity. Riser cable is suitable for vertical shafts not defined as an environmental air plenum. Riser Flame Test
General purpose cables meet UL 1581. Cable samples on a 8 feet vertical tray are burned at 20KW (70,000 BTU/Hr) for 20 minutes. The cable is deemed to pass the test if the flame spread will not extend to the upper portion and extinguish by itself. UL 1581 is similar to IEC 60332-3C, except for that the number of testing samples is different. This test does not look at the smoke density or toxicity. The CMG cables are usually used in runs penetrating single floor. This cable cannot be installed in vertical pathways. Vertical Tray Flame Test
This general purpose cables also meets UL 1581. CM and CMG are similar, both recognized in Canada and USA. This test does not look at the smoke density or toxicity. The CMG cables are usually used in runs penetrating single floor. This cable cannot be installed in vertical pathways. Vertical Tray Flame Test
The restricted cable meets UL 1581, Limited-use. The test consists of 25 feet long ventilated tunnel. The cable is placed on a ladder inside the tunnel and the flame of 30,000 BTU/Hr is applied to the cable 15 seconds on and 15 seconds off five times for a total exposure to the flame of 1 minute and 15 seconds. To quality for this test, after the test flame is removed, the cable can flame for not more than 60 seconds and the charred portion will not exceed by 25%. Vertical Wire Flame Test
UL 1581, VW-1 is similar to IEC 60332-1, except for the difference in the time for flame applied. This test does not look at the smoke density or toxicity. The CMG cable is suitable for use in. dwellings and for use in raceway. This cable cannot be installed in bundles and must be protected in metal conduit. This type of cable is the minimum requirement in commercial installations.
Fire resistant cables are designed for maintaining circuit integrity during a fire. Both the IEC and the BEC adopted two different standards, namely the IEC 60331 and BS 6387. Comparatively speaking, the fire performance requirement for BS 6387 is more demanding. IEC Fire Resistance Testing
IEC60331 Fire Performance Standard
Fire Performance Testing
A cable sample of 1200mm in length is placed over a gas burner and connected to an electrical supply at it’s rated voltage.Fire is applied for a period of 90min or 120min according to different specified standards. The temperature on the cable is 750℃ or 830℃
BS 6387 specifies the performance requirements for cables required to maintain circuit integrity under fire conditions. It details the following methods to categorize the cables according to cable withstand capacities.
Resistance to fire alone – the cables is tested by gas burner flame while passing a current at its rate voltage. Four survival categories are defined: Cat A (3hours at 650 ℃ ); Cat B (3 hours at 750 ℃ ; Cat C (3 hours at 950 ℃ ) & Cat S (20 minutes at 950 ℃ ).
Resistance to fire with water spray – a new sample of cable is exposed to flame at 650C for 15 minutes while passing a current at its rated voltage and then the spray is turned on to give exposure to both fire and water for a further 15 minutes. A single survival category W is defined if the cables surpassed the testing requirement.
Resistance to fire with mechanical shock – the final requirement is mechanical shock damage. A fresh sample is mounted on a backing panel in an S bend and is exposed flames while the backing panel is stuck with a steel bar with same diameter as the cable under test every 30 seconds for 15 minutes. The cables will be tested under the following temperatures: X (650 ℃), Y (750 ℃) and Z (950 ℃).
Vertical-tray flame tests are commonly used in the wire and cable industry to analyze cable flame propagation for industrial control and power cables. These tests specifically examine the flame spread on cables installed in a vertical test chamber, simulating real-world industrial cable conditions when installed in a cable tray or other support systems. Vertical-Tray Flame Tests
Standard cable flame-propagation tests benefit cable manufacturers, electrical distributors and end-users. These procedures provide consistent, repeatable results and measurable test acceptance criteria that allow the selection of the correct product for the application. The standard flame tests commonly specified in the industry are UL 1685, IEEE 1202, and IEEE 383.
UL 1685 Vertical-Tray Fire-Propagation and Smoke-Release Test for Electrical and Optical-Fiber Cables is an industry standard that provides the test methods for two types of vertical flame tests: ① UL Flame Exposure ② FT4/IEEE 1202 Type of Flame Exposure UL 1685 Standard
The UL version and the FT4/IEEE 1202 version both measure flame propagation by testing groups of cables. These tests vary in the cable loading, spacing, burner angle, flame spread and optional smoke requirements. UL cable standards provided in Table 1 allow control and industrial cables to meet one of the UL 1685 vertical flame tests to be UL listed.
UL Control and Instrumentation Cable Standards Containing Vertical Flame Tests
The UL Flame Exposure test of UL 1685 measures the flame spread in groups of cables in a steel ladder tray. The tray is 12 inches wide, 3 inches deep and 96 inches long. UL 1685 → UL Flame Exposure Test
The rungs measure 1 inch in the direction parallel to the length of the tray and are spaced 9 inches apart. The tray is mounted vertically on the floor of the test chamber or on an optional tray base and the center of the tray is filled with cable samples in one layer spaced 1/2 cable diameter apart.
A mixture of air and propane is burned using a ribbon burner. The burner is placed horizontally 3 inches from the surface of the cable, 18 inches from the bottom of the tray and midway between two rungs. The power output of the burner is 70,000 Btu/hr. The flame is applied for twenty minutes and then removed.
A cable passes the vertical-tray test if the cable char height is less than 8 feet. A cable may continue to burn after the burner is shut off.
However, The test is not complete until the cable stops burning. The UL Flame Exposure test also contains an optional smoke test. Cables that meet the smoke test have to meet the following requirements: (a) The total smoke released is to be 95 m² or less (b) The peak smoke release rate is to be 0.25 m²/s or less.
UL Flame Exposure Test Chamber's Inner Structure + FT4 IEEE 1202 Test Chamber Test Chamber's Inner Structure
The FT4/IEEE 1202 Flame Exposure version of UL 1685 is similar to the UL Flame Exposure version but contains a few variations. This test measures the flame spread in groups of cables in a steel ladder tray. The tray is 12 inches wide, 3 inches deep and 96 inches long. The rungs measure 1 inch in the direction parallel to the length of the tray and are spaced 9 inches apart. UL 1685FT4|IEEE 1202 Flame Exposure Test
The tray is mounted vertically on the floor of the test chamber or on an optional tray base. The tray is filled with cable samples. Depending on the outer diameter of the cable, different spacing requirements apply. A mixture of air and propane is burned using a ribbon burner.
The burner is placed at a 20° angle 3 inches from the surface of the tray, 12 inches from the bottom of the tray. The power output of the burner is 70,000 Btu/hr. The flame is applied for twenty minutes and then removed.
A cable passes the vertical tray test if the cable char height is less than 4 feet, 11 inches. A cable may continue to burn after the burner is shut off; however, the test is not complete until the cable stops burning.
The FT4/IEEE 1202 also contains an optional smoke test. Cables that meet the smoke test have to meet the following requirements: (a) The total smoke released is to be 150 m² or less (b) The peak smoke release rate is to be 0.40 m²/s or less
IEEE 383 is a Class 1E Nuclear Standard and provides requirements for cables and installations used in nuclear power generation facilities. IEEE 383 previously contained a flame test in the 1974 version but was updated in 2003 and again in 2015. IEEE 383 Flame Test
In 2003, the flame-test procedure was removed from the standard. Instead, IEEE 383-2003 Section 8 points users to IEEE 1202 as shown below: Cables shall be flame retardant in accordance with the requirements of IEEE Std 1202-1991 or NFPA 262-2002. Switchboard cables, coaxial, twinaxial, and triaxial cables shall as a minimum pass the UL VW-1 flame test.
Many existing cable specifications reference IEEE 383 in the cable flame-performance section for historical reasons. Based on the above reference, cables that meets the IEEE 1202 flame test meet the flame-requirements of IEEE 383.
The riser cables tests is designed to evaluate the fire-retardant properties of cables, including their ability to resist flame spread and minimize smoke generation during a fire incident. The test measures cable performance based on various parameters, including flame propagation, heat release rate, smoke density, and burning behavior. During the test, riser cables are subjected to high temperatures and fire exposure. The test evaluates whether the cables will pass or fail based on criteria such as char length and duration of sustained combustion. If your riser cables have passed this rigorous standard, you can rest assured that they meet industry regulations for safety and compliance.
related page logoFire Tests for Evaluating Wire & Cable Flammability|Cable Fire Tests – NFPA 262 Plenum Steiner Tunnel Test – UL 1666 Riser Cable Fire Test – UL 1685 Vertical Tray Tests – UL 1581 / UL 2556 VW-1 Vertical Flame Test
related page logoNIST Technical Note 1291|Fire Performance of Wire and Cable: Reaction-to-Fire Tests -A Critical Review of the Existing Methods and of New Concepts
related page logoUL 1666 Riser Cable Flame Test Equipment for Flame Propagation Height of Cables → China Manufacturer
related page logoCables And Wires Flame Resistance Test UL 1581 UL 2556 UL 1685|VW-1, FV-2/VW-1, FT1, FT2, UL 1581 Part 1090
Agencies like UL, CSA, ISO, and NEC define tests within their respective standards to determine a cable’s flame resistance capability. All these agencies consider the following aspects for flammability tests: ①Flame Propagation ②Smoke Generation and Propagation ③Additional Support for Combustion. The NEC focuses on fire hazards in buildings, while UL and CSA focuses on application requirements.
UL Flammability Tests: These are divided into one small, and two large scale flame tests. UL Flammability Tests
This is a small scale, vertical flame test. Cable that carry currents up to 500 Watts are subjected to this test. The UL 1061 is mainly used appliance wiring. UL 1061
This test is performed to check flame resistance of power and communication cables used in trays. The test is similar to the CSA FT4 flammability test, but not as stringent. UL Vertical Tray
This is also called a Riser Cable test. It is performed on cables that are used in vertical runs in a shaft. Like the UL vertical tray, the test is similar to the CSA FT4 flammability test, but not as stringent. UL 1666
These are divided into two small, and one large scale flame tests. FT1 and 2 are the small scale tests. CSA Flammability Tests
This is a vertical flame test that should only be performed on manufactured cables. The FT1 is mainly used to test industrial equipment wire or Appliance Wire Material (AWM) with 500W. FT1
This is a horizontal flame test that is performed on finished cables. It is a minimum and mandatory requirement for flame testing flexible cords. FT2
The FT4 test is designed to test cables, which are going to be installed and used in tray and shaft applications. FT4
There is a test that is defined by both UL and CSA organizations – VW-1. This is also a vertical flame test, but is performed on flexible cords, as well as finished cables with 500 W. VW-1
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