21.1 A general-use cord set (see Sections 17 – 27) employing flexible cord having No. 18 or No. 17 AWG
conductors shall be provided with overcurrent protection (short circuit and overload protection) rated equal
to or less than the ampacity of the flexible cord.
21.2 The overcurrent protective device shall have a minimum short circuit rating of 1000 A and shall be
of the replaceable or manually resettable type. A replaceable fuse shall be of a readily available type to
reduce the likelihood of the plug being replaced with one that is unfused. The overcurrent protective
device shall not be of the automatic resetting type.
Revised 21.2 effective June 1, 2003
21.3 The overcurrent protective device shall be located in the attachment plug or current tap, or be of a
through-cord design located so it is not more than 6 inches (152 mm) from the face of the plug to the rear
of the fuseholder.
21.4 Supplementary overcurrent protection is an acceptable method of providing the protection required
in 21.1, however, thermal cutouts, thermal relays, and other devices not intended to open short circuits
shall not be used.
21.5 The overcurrent protective device shall provide protection for each ungrounded circuit conductor but
not for any grounded circuit conductor or grounding conductor.
Exception: An overcurrent protective device may be used if it opens all circuit conductors – including the
grounded circuit conductor(s)– and cannot open the grounded circuit conductor without opening all
ungrounded circuit conductors.
以上是UL817中有關過流保護裝置的規定，上個月我向UL提交了一個我開發的將保險絲成型在5-15P插頭中的樣品（保險絲不可拆換式），UL以用戶可能會將插頭剪除，然後再配一個無保險絲的插頭為由，將我的案子close掉，現在，我想按照上述規范中的要求，在線材上裝一個可以手動回復的保險裝置，不知那位有這種裝置的供應商，可以介紹給我，或那位在這方面有經驗，可以給予指點。
