To install barn lights, install the sub-panel and underground feeder, and follow this up the receptacle and lighting branch circuits. Set the lights along the side or front walls within the barn so that shadows decrease. For barn exteriors, set big lights in vapor-tight fixtures. Protect wiring with metal or plastic conduits, and set switches within easy reach.
Choose a combination of general aisle way and individual stall lighting for a barn. Dig a trench from the main electrical panel location to the barn at a depth of 18 inches as defined by the National Electrical Code. Install the electrical cable and conduit, and mount the sub-panel as close to the barn entry as possible. Install the feeder cable, and connect circuit conductors to the circuit breaker.
Mount device boxes for light switches and duplex receptacles, and mount the lighting outlet boxes high enough so that they do not touch the horse. Install circuit breakers for receptacle groups and light branch circuits, and complete connections to the grounding bar. Connect the receptacles and light switches, and secure fixtures to their boxes. Opt for vapor-tight fixtures, as barns may be dusty or moist. Protect all electric wiring with conduit to prevent rodents chewing wires and causing a fire hazard.