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47.1.3.2 During these tests the converter or inverter is to be placed on a softwood surface covered with
a white tissue paper and a single layer of cheesecloth is to be draped loosely over the entire enclosure.
The cheesecloth is to be untreated cotton cloth 36 inches (910 mm) wide, running 14 – 15 yards per
pound (28 – 30 m/kg), and having, for any square inch, a count of 32 threads in one direction and 28 in
the other direction (for any square centimeter, 13 threads in one direction and 11 in the other direction).
Exception: Units not having any bottom openings need not be placed on a softwood surface covered with
tissue paper.
47.1.3.2 added January 27, 1995
47.1.3.3 The supply circuit is to have branch circuit overcurrent protection, the size of which equals 125
percent of the input current rating (20-ampere minimum), except where this value does not correspond
with the standard rating of a fuse or circuit breaker, the next higher standard device rating shall be used.
The test voltage is to be adjusted to the value specified in 31.1.
Exception: If a marking on the product indicates the use of branch circuit protection exceeding 125
percent of the input current, such protection shall be used.
47.1.3.3 added January 27, 1995
47.1.3.4 The enclosure of the unit is to be connected directly to ground.
47.1.3.4 added January 27, 1995
47.1.3.5 Each test is to be continued until further change as a result of the test condition is not likely. If
an automatically reset protector functions during a test, the test is to be continued for 7 hours. If a manual
reset protector functions during a test, the test is to be continued until the protector is operated for 10
cycles using the minimum resetting time, but not at a faster rate than 10 cycles of operation per minute.
The following are considered as an acceptable termination of the test:
a) Opening or shorting of one or more components such as capacitors, diodes, resistors, solid
state devices, printed wiring board traces, or the like.
b) Opening of the intended branch circuit overcurrent protection device.
c) Opening of an internal fuse.
Exception No. 1: If the manually reset protector is a circuit breaker that complies with the Standard for
Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures, UL 489, it is to be
operated for 3 cycles using the minimum resetting time but not at a rate faster than 10 cycles of operation
per minute.
Exception No. 2: A manual reset protector that becomes inoperative in the open condition may be
operated fewer than 10 cycles, but not less than 3 cycles.
47.1.3.5 revised September 11, 1998
47.1.4 The output short-circuit and specific-value-overload tests are to be conducted on the bench and
under the conditions described in 37.3.2 and 37.3.3.
Exception: A converter or inverter that employs integral fuses need not be subjected to the short-circuit
test under the conditions described in 37.3.2 and 37.3.3.
47.1.4 effective April 13, 1993
OCTOBER 15, 2004 UL 458 60A
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