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参考一下UL2021:
6 M& `, ^3 [. ^6 c15.2 Protection of wiring' z; V$ j, j5 l" [& X
15.2.1 The wiring and connections between parts of a heater shall be protected or enclosed, except that
6 j q& |) [( N" s6 ua length of flexible cord may be employed for external connections, or for internal connections that may. S2 c& {; O3 j4 D8 @
be exposed during servicing, if flexibility of the wiring is essential.* }4 I0 Z5 g, c; ?5 M# G
15.2.2 The internal wiring of a heater in the vicinity of a lampholder that accepts either an infrared lamp) d. w- Q+ w3 A3 T3 {# Q9 q5 l
or an ordinary lamp:6 E% m5 }8 r! m: b3 I: W/ p- A. j
a) Shall be a jacketed type at least equivalent to Type SP-2 flexible cord. Asbestos-insulated
" V( |+ X5 a9 N; Ewiring and appliance wiring material is not acceptable unless provided with sleeving or tubing., A G. ]+ R; ^
b) Shall be routed along the metal surface of the heater enclosure and shall be so secured as
6 b- R& n' q" n6 d& P) _to minimize the likelihood of its being hooked or grasped.
* o- C V4 h- K9 w2 [* f15.2.3 A conductor utilizing beads for insulation shall not be used outside an enclosure.
: |0 \7 l2 i, x8 y' \15.2.4 Internal wiring that is exposed through an opening in the enclosure of a heater is considered to be# ~( n6 P+ i+ |: k
protected as required in 15.2.1 – 15.2.3 if, when judged as though it were film-coated wire, the wiring' B0 m" M* q3 k/ ]) m
would be acceptable according to 7.17– 7.20. Internal wiring within an enclosure is acceptable if, even
- e/ E1 k$ z$ J# h& K& ^( X$ `( A; a0 c/ Tthough it can be touched with the probe, it is so protected or guarded that it cannot be grasped or hooked* J& u3 M# [) l( n. }8 a
in such a manner that it could be subjected to stress. |
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