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Description / Abstract:
These requirements cover the fire test investigation of
electrical circuit protective systems of various materials and
construction.
Under these requirements, samples of electrical circuit
protective systems are exposed to an external fire for a
predetermined time, and then to an application of a water hose
stream. The following measurements and determinations are made
during the fire exposure and water hose stream tests:
a) Measurement of temperature changes within the electrical
circuit protective system caused by the heat transfer through the
electrical circuit protective system to the electrical conductor or
raceway, or both, during the external fire exposure test.
b) Determination of the integrity of the electrical circuit
protective system during the external fire exposure and water hose
stream test.
c) Determination of the ability of insulated electrical
conductors to maintain electrical circuit integrity at the
temperature conditions present within the electrical circuit
protective system during the external fire exposure test and during
the water hose stream test.
The external fire exposure and water hose stream test may be
cited as the "Standard Fire Test," and the performance is expressed
in terms of maximum temperature rise within the electrical circuit
protective system at various increments of fire exposure time.
The external fire exposure and water hose stream tests may not
be representative of all fire conditions; conditions may vary with
changes in the amount, nature, and distribution of fire loading,
ventilation, compartment size an configuration, and heat conducting
and dissipating characteristics of the compartment in which the
electrical circuit protective system is installed. These
requirements provide a relative measure of fire performance of
comparable assemblies under these specified fire exposure
conditions. Any variation from the construction or operating
condition tested, such as size, method of assembly, and materials,
may substantially change the performance characteristics of the
system.
These requirements also cover sample systems which are subjected
to an internal fire exposure to evaluate their ability to contain
fires originating within the electrical circuit protective system
if, for example, the system contains ventilation means such as
holes, slots, louvers, or dampers. The internal fire exposure test
may be waived at the discretion of the testing body if the material
or installation, or both, obviate the need for such testing.
These requirements do not cover:
a) Accumulation of data as to performance of electrical circuit
protective systems constructed with components or sizes other than
those tested.
b) Evaluation of the contribution of the electrical circuit
protective systems to generation of smoke, toxic gases, or other
products of combustion.
c) Measurement of flame spread over the surface of the tested
elements.
d) Evaluation of the firestop system in floor openings
penetrated by the electrical circuit protective systems, unless
specifically provided for in the system tested.
e) Evaluation of the ampacity of electrical conductors within
the electrical circuit protective systems.
The results obtained by use of this test method are intended to
develop data that will assist authorities having jurisdiction, and
others, in determining the acceptability, with reference to circuit
integrity, of electrical circuit protective systems for use with
specific electrical conductors in specific applications.
Tests for burning characteristics of building materials, based
on rate of flame spread and the density of smoke developed when
exposed to a standard fire, can be found in the requirements for
surface burning characteristics of building materials, UL 723.
Tests for fire resistance of firestop systems which penetrate
through walls and floors can be found in the requirements for
Through-Penetrate Firestop Systems, UL 1479.
By the prescribing of the standard fire and water hose stream
exposures for comparing the performance of electrical circuit
protective systems, the results of these tests represent one factor
in determining the acceptability, with reference to circuit
integrity, of electrical circuit protective systems for use with
specific electrical conductors in specific applications.
Application of these test results to predict circuit integrity of
electrical conductors in actual installations requires careful
evaluation of the electrical conductor insulation materials and the
temperature within the electrical circuit protective system under
normal operating conditions.