UL 555C-2021 pdf free download.Ceiling Dampers. 6 Fire Endurance Test 6.1 Test assembly 6.1.1 The ceiling damper or ceiling air diffuser shall be installed in a ceiling of a type previously tested in a rated fire resistive floor-ceiling or roof-ceiling assembly. Each test assembly shall indude a reference hinged-door type damper installed in a floor-ceiling test construction identical to that used with the ceiling damper or ceiling air diffuser installation. The ceiling compartments containing the reference hinged-door damper and the ceiling damper or ceiling air diffuser shall be separated by means of an insulated wall or barrier to prevent heat transfer from one ceiling compartment to the other during the fire test. 6.1.2 The duct outlet provided with the reference hinged-door damper is to be representative of the smallest duct outlet size for which comparative performance data is desired. The comparative performance data shall apply to hourly rated assemblies incorporating hinged-door sheet metal type dampers protecting duct outlets of the size tested and larger. 6.1.3 The area of each ceiling construction exposed to fire shall not be less than 48 ft2 (4.5 m2), with neither dimension less than 70 in (1.8 m). The dimensions of the ceiling incorporating the reference hinged-door damper and the dimensions of the ceiling with the ceiling damper or ceiling air diffuser shall be identical. 6.1.4 Ceiling dampers and ceiling air diffusers tested in ceilings with exposed grid suspension systems are eligible for installation in ceilings of rated assemblies with exposed or concealed grid suspension systems or with “hard” ceilings of gypsum wallboard or plaster. Ceiling dampers and ceiling air diffusers tested in ceilings with concealed grid suspension systems are eligible for installation only in ceilings of rated assemblies with concealed grid suspension systems or with Thard” ceilings of gypsum wallboard or plaster. Ceiling dampers and ceiling air diffusers tested in “hard” ceilings of gypsum wallboard or plaster are only eligible for installation in rated assemblies with “hard” ceilings, The ceiling dampers or ceiling air diffusers shall be tested in a ceiling incorporating the least number of ceiling hanger wire supports in the vicinity of the air-handling opening as specified for the rated assemblies in which the ceiling damper or ceiling air diffuser is intended to be installed. 6.1.5 The floor is to consist of cellular steel floor units topped with structural or non-structural concrete or sand. The cellular steel floor units shall be provided with...
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