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UL 14129 z4 M" C" H( s# o% X! K. I* g
15 Overload Test) u# O8 V+ `% U
15.1 A resistor shall withstand the overload test described in this section without resulting in a fire.
$ q. q& z& D( T* U15.2 A single layer of cheesecloth is to be wrapped around, and be in contact with, the resistor under test.3 X1 b" H9 R/ ^, i, P6 ^1 y6 C
Exception: At the manufacturer’s option, the cheesecloth may be spaced 1/2 inch (127 mm) – or 1 inch
3 C7 b) w" y& p/ T! d(25.4 mm) for a resistor rated greater than 10 W – from the resistor body as described herein. In this case,4 d9 V9 S8 H }6 N7 S2 K
a positive spacing of 1/2 inch (or 1 inch, as appropriate) between the resistor body and combustible" I' O/ ~# Z: c
materials is to be provided in the complete appliance. A single layer of cheesecloth is to be placed around
; \- C" \. O* G- {7 [2 z% K. F( rthe resistor under test to form a cylinder with open ends. The length of the cylinder is not to be less than
, e# ~& W! g5 P$ Cthree times the length of the resistor body and the diameter of the cylinder is to be such that the; t$ d3 C) D5 H. {2 d! i3 V, X y
cheesecloth is spaced 1/2 inch (or 1 inch, as appropriate) from the outermost part of the resistor body.( w9 L8 R5 O2 Y; B( q8 ]) b
The resistor body is to be centered end-to-end within the cylinder and the longitudinal axis of the resistor: u0 K( z4 i$ J5 S
body is to be coincident with the longitudinal axis of the cylinder.
0 E9 V& e4 Y1 _1 t4 G15.3 The resistor is to be connected to a 60-Hz variable voltage source of supply fused at 30 A. Prior to1 I# G9 q) m% M" m' W/ e' C$ f) c
energizing, the supply voltage is to be adjusted to produce rated current (or rated power dissipation) in% x& z9 m! J: Y
the resistor. At 1-minute intervals after energizing, the supply voltage is to be raised in steps of 2, 3, 4, 5,
+ {% v9 t: c* R+ Q& F: }( K0 aand so forth, times that initial voltage until the resistor opens. In no case is the voltage rating of the resistor5 J) k( i; T) Q$ U9 S2 h4 y
to be exceeded.
& ]) U1 D8 o* v! h2 k+ }# X15.4 Five complete separate tests are to be made using new samples for each test.3 c! y7 D7 K2 i2 h3 m! b
15.5 The results are not acceptable if the cheesecloth flames.* Z4 Y- o+ Z9 F4 w( ~
15.6 The cheesecloth used for the overload test shall be untreated cotton cloth 36 inches (0.9 m) wide,
7 z: J0 }: g6 P9 a. N, |; _running 14 – 15 yd2 /lb and having what is known to the trade as a count of 32 by 28. |
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