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参考一下UL2021:
7 x {, e1 H! I6 N# U15.2 Protection of wiring
' C m- J% I V9 I/ W15.2.1 The wiring and connections between parts of a heater shall be protected or enclosed, except that
* j: F; [. V7 D/ s' q- a9 R' A7 Pa length of flexible cord may be employed for external connections, or for internal connections that may8 K% _6 s) _: O+ R9 ~
be exposed during servicing, if flexibility of the wiring is essential.
3 \ r, |+ Y' \3 W* k: ?15.2.2 The internal wiring of a heater in the vicinity of a lampholder that accepts either an infrared lamp3 m3 R3 |8 o6 z0 |. Z6 g/ R
or an ordinary lamp:
i7 P( z) \7 p6 D7 T* Ea) Shall be a jacketed type at least equivalent to Type SP-2 flexible cord. Asbestos-insulated
, i0 r5 C! i) f; f$ ^3 j" b! twiring and appliance wiring material is not acceptable unless provided with sleeving or tubing.5 e* ^* J9 |4 s- J5 |+ S- i8 w
b) Shall be routed along the metal surface of the heater enclosure and shall be so secured as4 S4 q9 [9 k! Z1 `
to minimize the likelihood of its being hooked or grasped. J, _8 J9 Q7 a# w
15.2.3 A conductor utilizing beads for insulation shall not be used outside an enclosure.2 f. i) o) c& p+ g% j |
15.2.4 Internal wiring that is exposed through an opening in the enclosure of a heater is considered to be8 n- Y, z m- a8 I" u5 V3 ` L6 A
protected as required in 15.2.1 – 15.2.3 if, when judged as though it were film-coated wire, the wiring$ h b2 i* C9 Q K: ]( p/ N; H( ^
would be acceptable according to 7.17– 7.20. Internal wiring within an enclosure is acceptable if, even
" w. ]/ T; A# R" {$ d9 |though it can be touched with the probe, it is so protected or guarded that it cannot be grasped or hooked( J+ j+ t7 C {( x! v- E4 h$ v( x8 d) \
in such a manner that it could be subjected to stress. |
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