Comparison of large‐and small‐scale heat release tests with electrical cables

A total of 21 electrical cables were made, all with identical construction but differing in the chemical composition of their plastic components, both jacket (or sheath) and insulation. All the compounds used were commercially available materials, but they covered a variety of polymers, both halogenated and non‐halogenated. All cables were tested in a large‐scale cable tray test, the proposed ASTM D9.21 test, based on the IEEE 1202 or the CSA FT‐4 test, modified to measure heat and smoke release in the duct and with a total length of 2.44 m. The peak rate of heat release measured served as an excellent criterion for distinguishing between cables passing and failing the test (the traditional criterion being char length). The average rate of heat released also served to distinguish the two classes of cables. Moreover, cables passing the test tended to release less smoke than those failing the test. The cables were also tested in the IEC 332‐3 cable tray test. The small‐scale fire test used for the cables was the cone calorimeter, ASTM E 1354. The trends observed in this heat release test were similar to those in the large‐scale test. The results indicate that cables with excellent fire performance can be made by using a variety of materials, so that it would seem to follow that it is important to specify fire performance and leave material choice to manufacturers.