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Table 28.1
Spacings for converters or inverters intended for use in a general environment
Table 28.1 revised September 11, 1998
Involved in V
RMS (peak)
Minimum spacings, inch (mm)
Between any uninsulated live part and an uninsulated live part of
opposite polarity, uninsulated grounded part other than the
enclosure, or exposed metal part
a
Between any uninsulated live
part and the walls of a metal
enclosure including a fitting for
conduit or armored cable
b
,
shortest distance
Through air Over surface
0–50
(0 – 70.7) 1/16 (1.6)
c
1/16 (1.6)
c
1/16 (1.6)
c
51 – 150
(70.7 – 212.1) 1/8 (3.2)
c
1/4 (6.4) 1/4 (6.4)
151 – 300
(212.1 – 424.3) 1/4 (6.4) 3/8 (9.5) 1/2 (12.7)
301 – 600
(424.3 – 848.5) 3/8 (9.5) 1/2 (12.7) 1/2 (12.7)
a
For printed wiring boards, see Exception Nos.2–4to28.1.1.
b
For the purpose of this requirement, a metal piece attached to the enclosure is considered to be a part of the enclosure if
deformation of the enclosure is likely to reduce spacings between the adjacent metal piece and uninsulated live parts.
c
The spacing between field-wiring terminals of opposite polarity and the spacing between a field-wiring terminal and a
grounded dead-metal part shall not be less than 1/4 inch (6.4 mm).
DECEMBER 14, 1993 UL 458 39
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