IEEE 848:2015 pdf free download – IEEE Standard Procedure for the Determination of the Ampacity Derating Factor for Fire-Protected Cable Systems
4.2.3 Conduit
Conduit ampacity tests shall utilize 25 mm and 100 mm (l in and 4 in) rigid steel conduits.Tests conductedusing these two sizes shall be considered representative of all sizes provided that the fire-protective systeminstallation methods and configurations are consistent across the entire size range. Where the installationmethods, configurations, or fit differ according to conduit size, the user shall test sizes to bound the specificapplication.Conduits shall be a minimum 3660 mm (12 ft) long. The conduit shall be isolated from itssupporting structure by wooden blocks.
The surface emissivity of the conduit can affect test results. In order to provide a mechanism that will allowcomparison of test results, the average surface emissivity of the conduit, along with the measuring device,shall be documented.The average surface emissivity of the conduit shall be determined at a minimum ofnine points. Each test point should be a minimum of 305 mm (1 ft) from any other test point. Conduitcouplings emissivities shall not be utilized in the calculation to determine the average surface emissivity.In addition to the conduit，the junction boxes and pull boxes may also be enclosed with a protectivematerial. Since the surface area of the boxes is significantly greater than the conduit，heat transfer isimproved proportionally.Therefore，junction boxes and pul boxes do not need to be included in theampacity test.
4.2.4 Tray
A commercially available 100 mm (4 in) deep,610 mm (24 in) wide ladder-back style steel cable tray, aminimum of 3660 mm (12 ft) long, shall be used. The tray shall be isolated from the support by woodenblocks.
Ampacity correction factors developed for ladder-back style trays will not be applicable to solid bottomtrays. If fire-protective material is intended for use with alternate tray configurations such as solid bottomor ladder-back with removable top or bottom covers,separate testing must be performed for both thebaselinc and protected conditions. Users of this standard must also ensure that configurations that result indead air spaces between covers and cables or between covers and protective materials are adequatelyreproduced in the baseline and wrapped test specimens as such gaps can significantly impact results.
4.2.5 Free-air drop
Ampacity tests shall be conducted on free-air drop configurations consisting of 4/C No.10 AWG and 123/C No.6 AWG,respectively. Tests conducted using these two sizes shall be considered representative ofall sizes provided that the fire-protective system installation methods and configurations are consistentacross the entire size range. Where the installation methods, configurations, or fit differ according to size,the user shall test sizes to bound the specific application.Free-air drops shall be a minimum of 3660 mm(12 ft) long. The test specimen shall be supported to prevent sagging and shall be isolated from itssupporting structure by woodcn blocks.
4.2.6 Fire-protective material
The protective material shall be representative of the installed product at maximum thickness. If theproduct is typically applied in a non-uniform manner, c.g., joints overlap when product is butted, then thesesections shall be included in the test.
Some fire-protected cable systems utilize an end seal at the barrier or wrap ends in order to prevent theintrusion of hot gases or fire into the end of the tray or conduit. If the end seal is less than 150 mm(6 in)thick, then the seal may be excluded from the test. Otherwise, the end seal should be treated and tested in asimilar manner to a cable fire stop, except the wall section will be excluded.