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Subchapter 5. Electrical Safety Orders
Group 2. High-Voltage Electrical Safety Orders
ARTICLE 20. INTERRUPTING AND ISOLATING DEVICES
(a) Use. Where fuses are used to protect conductors and equipment, a fuse shall be placed in each ungrounded conductor.
(1) Parallel (Multiple) Power Fuses. Two power fuses shall be permitted to be used in parallel (multiple) to protect the same load, provided:
(A) Both fuses have identical ratings, and
(B) Both fuses are installed in an identified common mounting with electrical connections that will divide the current equally.
(b) Vented Power Fuses. Power fuses of the vented type shall not be used indoors, underground or in metal enclosures unless identified for the use.
(c) Interrupting Rating. The interrupting rating of power fuses shall equal or exceed the maximum fault current the fuse will be required to interrupt, including contributions from all connected sources of energy.
(d) Voltage Rating. The maximum voltage rating of power fuses shall equal or exceed the maximum circuit voltage. Fuses having a minimum recommended operating voltage shall not be applied below this voltage.
(e) Installation. Fuses shall be installed in suitable metal enclosures.
Exception: Fuses shall be permitted to be installed without metal enclosures in substations, vaults, or outdoor locations.
(f) Structure Mounted Indoor or Outdoor. The height of fuse mountings on structures shall provide safe clearance between lowest energized part (open or closed position) and standing surface. For mounting heights, see Article 35.
(g) Disconnecting Means. A suitable means shall be installed to isolate each fuse from all sources of potential. Provision for installation and removal of the fuse by suitable live line tools meets this requirement.
(h) Identification of Fuse Mountings and Fuse Units. The fuse mountings and fuse units shall be permanently and legibly identified to include the following information: manufacturer's type or designation, continuous current rating, interrupting current rating, and maximum voltage rating.
(i) Clear Workspace. Space shall be provided for fuse handling in accordance with Article 35.
(j) Door Interlock. Means shall be provided to prevent access to fuses installed in metal enclosures until all sources of energy are disconnected.
(k) Enclosed Fuse Types. Fuses installed in metal enclosures shall be of the non-vented or controlled-vented type. Adequate volume or other means shall be provided to prevent the operation of fuses from causing dangerous pressures in enclosures.
(l) Fused cutouts installed in buildings or transformer vaults shall be of a type approved for the purpose. They shall be readily accessible for fuse replacement.
4. Change without regulatory affect redesignating subsections (b) through (k) as (c) through (l) filed pursuant to section 100, Title 1, California Code of Regulations (Register 91, No. 7).
5. Removal of article 23 heading and amendment of subsection (a)(1)(B) filed 4-1-2009; operative 4-1-2009. Submitted to OAL for printing only pursuant to Labor Code section 142.3 (Register 2009, No. 14).