OSHA 1910.303 covers details about general safety guidelines related to electrical systems.
All electrical conductors or equipment required or permitted to be used only if it is approved as defined in 190.399 (Definitions). Some of the important safety guidelines are listed below:
- Electrical equipment which is installed or used shall be free from any type of hazard which may lead to death or serious physical harm to employees. The safety of the equipment shall be determined based on parameters such as suitability for installation, mechanical strength & durability, electrical insulation strength, wire bending & connection space, heating effects of equipment under all operating conditions, arcing effects, classification based on type, size, voltage, current, capacity, and other safeguarding parameters.
- Electrical equipment which is listed or labeled shall be installed and used as per the instruction details provided
- Wiring installations which are completed shall be free from any short circuits or ground faults
- Electrical equipment provided for interrupting the current at fault levels shall have a sufficient interrupting rating for normal circuit voltage and current levels that are available at equipment line terminals. Electrical equipment that is supposed to interrupt the current other than fault current levels shall have interrupting ratings such that at nominal circuit voltage levels, the equipment shall interrupt the current.
- Overcurrent protection device selection & trip settings and circuit characteristics shall be coordinated such that during a fault conditions, the operation of the overcurrent protection device shall isolate the fault without creating extensive damage to circuit electrical components. Occurance of the fault can be either between two or more conductors (phase faults) or between the conductor(s) and ground.
- No electrical conductor or electrical equipment shall be installed or located in damp or wet conditions unless it is identified for use in such an operating environment. When a conductor or equipment is exposed to such environments ( gases, fumes, vapors, liquids, excessive temperatures, or other agents & materials causing deterioration effect), equipment loses insulation strength leading to failure of equipment or resulting in short circuits.
- Electrical conductors and equipment shall be installed in a neat and workmanlike manner. All unused openings in boxes, raceways, and cabinets shall be effectively closed. Internal parts of the electrical equipment (busbars, terminals, and insulators) shall not be contaminated or damaged by foreign materials such as paints, plasters, or abrasives.
- Electrical equipment shall be properly secured and mounted on a surface. Electrical equipment is provided with the proper cooling natural circulation of air so as to remove any heat generated during its operation. It has to be taken care that no hindrance in the flow of air over the equipment’s surface or exposed parts due to walls or adjacent equipment.
- Arcing parts of the electrical equipment shall be vulnerable to arcing during the operation of electrical equipment shall be enclosed and isolated from any combustible material.
- Disconnecting means of the electrical equipment shall be capable of locking in the open position
- For carrying out operation and maintenance activities of the electrical equipment (voltage rating less than 600 V) sufficient space clearances shall be provided. The width clearance required for performing the operation shall be 30 inches or width of the equipment whichever is greater. Working space depth clearances required shall be as given in Table S-1. Distance for clearance shall be considered from the live parts in case if they are exposed or from the front part of the cabinet or enclosure if closed. Proper headroom for all the working spaces shall be provided as per OSHA requirements (if the electrical installation operating at a voltage rating below 600 V is built before Aug 13, 2007, the minimum headroom required is 6.25 ft, and in case the electrical installation is built on or post-Aug 13, 2007 minimum headroom required is 6.5 ft).
- Proper lighting (illumination) shall be provided for all the working spaces (for all the cabinets, switchgear panels, motor control centers, and other electrical equipment enclosures) installed indoors.
- All the electrical equipment live parts operating at voltage ratings at or above 50 V shall be guarded against accidental contact by unauthorized personnel by suitable rooms, vaults, enclosures, partitions, screens, or by elevation above 8 ft or more from the floor or working surface.
- In case of electrical conductors or equipment operating at 600 V or above, the electrical installation shall be accessible to non-authorized personnel by enclosing the installation in rooms, vaults, screens, or fences. If the installation is located outdoors, it has to be separated or isolated from unauthorized personnel with a fence not less than 7 feet in height. If the installation is located indoors, it has to be enclosed in metal-enclosed panels or cabinets and shall be locked or isolated for access from unauthorized personnel and proper caution signs shall be marked. If the bottom of the metallic or non-metallic enclosure housing electrical equipment is less than 8 feet above the floor or working surface, the hinged cover or enclosure door shall be kept locked.
- Working space required for electrical installation with a voltage rating at or above 600V when live parts are exposed shall not be less than 6.5 feet in height (measured from the floor or working platform vertically up) and 3 feet in width from live parts.