Current through Register Vol. 54, No. 45, November 9, 2024
Section 39.177 - Guarding live parts(a)Enclosure. Switchboards operating at over 300 volts to ground and located near passageways shall be guarded from these by suitable inclosures or barriers and shall be made inaccessible to other than authorized persons, unless under constant attendance during operation.(b)Mats. For the protection of the operator, if parts over 300 volts to ground are not otherwise guarded or isolated by elevation, suitable insulating floors, mats, or platforms providing good footing shall be so placed that the operator does not readily touch the live parts, unless standing on such floors, mats, or platforms.(c)Parts over 750 volts on face of board. No switchboard shall have exposed on its face within six feet from floor line any current-carrying part over 750 volts, except as noted in subsection (e) and except direct current railway boards up to 1,500 volts, which, if above nominal 750 volts, shall be so constructed that the operator does not inadvertently come in contact with parts having a hazardous difference of potential. Dead face panels and remote control should be utilized to achieve this result if isolation by elevation is impracticable or undesirable.(d)Exposed live parts on face or back. When working space adjacent to live parts are not provided in accordance with § 39.104 (relating to working space about electrical equipment), suitable guards shall be arranged to protect the operator from accidental contact with parts over 750 volts. Suitable insulating guardrails, sufficiently spaced from the face or back of the board, or suitable guards perpendicular to the face or the back of the board, and extending out beyond the live parts should be used, if practicable.(e)Plug-type switchboard. Plug-type switchboards shall, except while connections are being changed, have no current-carrying part exposed on face of boards and, if practicable, they and their plug connectors shall be so arranged where the operating voltage exceeds 150 as to have current-carrying parts guarded so long as they are alive, even while connections are being changed.(f)Instruments. Metal cases of instruments, unless isolated by elevation, operating at over 750 volts should be grounded or enclosed in suitable covers of insulating material or of grounded metal.(g)Exposed parts over 7,500 volts. No switchboard shall have current-carrying parts above 7,500 volts exposed unguarded unless these parts are effectively isolated by elevation, except at times when occasionally left exposed by removal of covers or entrance into enclosures, such as switch and instrument transformer cells or compartments, which are ordinarily unoccupied by persons. For such parts, if exposed while alive for any purpose, including busses and disconnectors in compartments, working space shall be provided complying with the requirements under § 39.160(d) (relating to guarding live parts of switches and automatic cut-outs not installed on switchboards). This section cited in 34 Pa. Code § 39.171 (relating to accessibility and convenient attendance).