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28.1.8 If an uninsulated live part is not rigidly secured in position by means other than friction between
surfaces, or if a movable dead metal part is in proximity to an uninsulated live part, the construction shall
be such that, for any position resulting from turning or other movement of the parts in question, at least
the minimum acceptable spacings will be maintained.
Exception No. 1: The spacing requirements in Tables 28.2 and 28.3 do not necessarily apply to the
inherent spacings of a component of a converter, such as a switch, fuse, or attachment plug. Such
spacings are to comply with the requirements for the component in question if they are less than the
values specified in Tables 28.2 and 28.3.
Exception No. 2: As provided in 28.2.1.
28.1.8 effective April 13, 1993
Table 28.3
Minimum acceptable spacings between an uninsulated live part and a metal enclosure or other
accessible dead metalpart, including a fitting for conduit or armored cable
Potential involved, volts Minimum spacing through air and over surface
inch (mm)
50 or less 1/16 (1.6)
51 – 150 1/4 (6.4)
151 – 230 1/2 (12.7)
28.1.9 With reference to 28.1.8, a properly applied lock washer is considered an acceptable method of
rigidly securing a part.
28.1.9 effective April 13, 1993
28.1.10 With respect to determining spacings, an uninsulated live part is considered to be at opposite
polarity to uninsulated live parts in another circuit. Spacings are to be based on the highest of the circuit
voltages.
28.1.10 effective April 13, 1993
28.1.11 Film-coated wire is considered to be an uninsulated live part when determining spacings.
28.1.11 effective April 13, 1993
28.1.12 Spacings at field wiring terminals are to be measured with conductors installed in the terminals.
The gauge of the conductors is to be based on the rating of the circuit containing the terminals.
28.1.12 effective April 13, 1993
28.1.13 Spacings between uninsulated live parts of different potential and between such parts and dead
metal that may be grounded in service are not specified for parts of low-voltage limited energy circuits in
accordance with 2.14. Spacings are determined by the applicable dielectric voltage withstand test
specified in Section 39, Dielectric Voltage-Withstand Test.
28.1.13 revised September 11, 1998
DECEMBER 14, 1993 UL 458 41
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