OSHA covers requirements for the provision of temporary wiring & wiring methods, associated equipment, and component details in OSHA Clause 1910.305.
General Wiring Methods:
The wiring system is not permitted to be installed in any ducts or shafts which carry flammable vapors, dust, or loose stack. Branch circuit wiring for electric equipment which is sensitive to electrical noise (electromagnetic interference) shall be isolated from raceways containing other branch circuit conductors. Metal raceways, cable trays, cable armor & sheath, and other non-current carrying parts of the electrical equipment shall be effectively bonded
Temporary Wiring:
In the case of temporary wiring provisions for electrical equipment, OSHA has stipulated the following requirements:
Temporary wiring supplying electrical power to installations & lighting loads rated at voltage 600V or less shall be used only for less than 90 days for any carnivals, Christmas, or other special purpose events. It shall be provided in case of any experimental or developmental works or in case of emergencies. It shall also be provided during any repairing, remodeling, or maintenance works carried out.
After completion of specific requirements for which temporary wiring is provided, has to be removed after completion of a specific purpose.
Electrical installations which are temporary in nature for use (experiments, emergencies, construction or other specific activities) rated at 600V or above, power supply to electrical equipment can be provided through temporary wiring
Temporary feeders supplying electrical installation shall originate from an approved distribution center. These feeder conductors connecting electrical installation shall run through multi-conductor conductor cords. In case these feeders are accessible by qualified persons, temporary feeders can be through single insulated cables.
Branch circuits supplying power temporary power supply to electrical installations shall originate from an approved panel board or outlet. These circuits shall not be laid on the ground for supplying power to the electrical equipment or installations. These conductors shall be routed through multi-conductor cords or cables and shall be fastened at every 10 feet interval to the ceiling. In the case, if the branch circuits are run as open conductors supplying power to electrical equipment or connected to receptacles, a separate equipment ground conductor shall be provided
Temporary wiring shall not use any earth return conductors or bare conductors while supplying power to electrical equipment or installations.
A disconnect means (switch, circuit breaker, or plug connector) shall be provided which is permitted to disconnect all the ungrounded branch conductors of the temporary wiring. In the case of multi-wire branch circuits that originate from a panel board or the power outlet, a disconnecting means shall be provided for isolating all the ungrounded conductors of the multi-wire branch circuits at the panel board.
Proper care shall be taken in case of flexible cords, cables, and cable assemblies used in temporary wiring against any accidental physical damages which may arise at sharp edges, projections, and doorways. Proper support at regular intervals shall be provided at regular intervals.
All illumination lamps shall be protected using lamp holders with guards against any accidental contact.
Cable Trays:
Type MV cables that are prone to sunlight exposure shall be identified as sunlight exposure resistant. Welding cables supplying power to welding equipment shall be placed in dedicated cable trays and shall not be mixed with other cables in cable trays. Cable trays located in hazardous locations shall house cables that are permitted in such locations. In the case of hoistway systems cable trays shall not be used as they are subjected to physical damage.
Open Wiring on Insulators:
Wiring conductors with insulator support in an open environment are provided for supplying power to electrical equipment or installation operating at a voltage of 600 V nominal or less in the case of industrial or agricultural applications. Open wiring conductors of size smaller than No.8 shall be supported on insulators within 6 inches from a tap or slice. These wiring conductors shall be supported at regular intervals not more than 4.5 ft in length. In case the conductors are routed through dry locations where they are not exposed to any physical damage, they can be routed through separately enclosed flexible non-metallic tubing with a length not exceeding 15 ft and supported at least at 4.5 ft intervals. If these conductors cross any ceiling joints or walls and are prone to physical damage, proper protection shall be provided. Protection shall be provided for the cable conductors which are entering the boxes or cabinets against abrasion. All the unused openings in boxes or cabinets shall be closed effectively.
Switches:
Single throw knife switch which is used to make or break the circuit shall be approved to be used in an inverted position along with a locking device such that it remains in an open position when in a set position. Double-throw knife switch shall be mounted such that it can be operated vertically or horizontally. In the case of vertical closure with a locking device, it shall be ensured that it remains in an open position when in the set condition.