UL 263:2015 free download Fire Tests of Building Construction and Materials
3.3 Temperatures of unexposed surfaces of floors, roofs, walls, and partitions
3.3.1 Temperatures at unexposed surfaces are to be measured with thermocouples or thermometers (under certain condition it may be impracticable to use thermometers), placed under flexible, dry, felted pads. The properties of these pads shall comply with the requirements specified in Requirements for Thermocouple Pads, Appendix B. 3
.3.2 The wire leads of the thermocouple or the stem of the thermometer are to have an immersion under the pad and be in contact with the unexposed surface for not less than 3-1 /2 ins (88.9 mm). The hot junction of the thermocouple or the bulb of the thermometer is to be placed approximately under the center of the pad. The outside diameter of protecting or insulating tubes and of thermometer stems is to be not more than 5/1 6 in (7.9 mm). The pad is to be held firmly against the surface and is to fit closely about the thermocouples or the thermometer stems. Thermometers are to be of the partial immersion type with a 3-in (76.2-mm) length of stem measured between the end of the bulb and the immersion mark. The wires for the thermocouple in the length covered by the pad are not to be heavier than No. 1 8 B&S gage [0.04 in (1 .02 mm)] and are to be electrically insulated with heat- and moisture-resistant coatings.
3.3.3 For the purpose of testing roof assemblies, the ″unexposed surface″ is defined as the surface exposed to ambient air.
3.3.4 Temperature readings are to be taken at not less than nine points on the surface. Five of these are to be symmetrically disposed, one at approximately the center of the specimen and four at approximately the center of its quarter sections. The other four are to be located at the discretion of the testing body to obtain representative information on the performance of the construction under test. No thermocouple is to be located nearer to the edges of the test specimen than one and one-half times the thickness of the construction, or 1 2 in (305 mm), unless necessary to include an element of the construction not otherwise represented in the remainder of the test specimen.
3.3.5 Thermocouples located opposite or on top of fasteners, such as screws, nails, or staples that will be obviously higher or lower in temperature than at more representative locations, are not to be used in determining the classification period if: a) The aggregate area of any part of such fasteners projected to the unexposed surface is less than 0.8% of the area within any 5-in (1 27-mm) square area, and b) The fasteners do not extend through the assembly.
UL 263:2015 free download
