For internally illuminated fluorescent signs, always install plug bolts in the holes that remain after the hoisting hardware is removed. And never place access doors or covers on the top of a sign cabinet, where water will leak in. Despite all of your best precautions, some water will still make its way into your sign. So use horizontal lamps whenever possible to keep lamp sockets away from the bottom of the sign, where water collects. Ballasts should not be mounted on the bottom of the sign cabinet, even though many sign manufacturers continue this practice.
Water can easily seep between the seams of the ballast case and short out the internal wiring.
Ballasts mounted vertically on the sides of the cabinet, or attached to the internal supports above the bottom of the cabinet, are much more resistant to moisture. Moisture is also a problem at the base of sign poles. Steel anchor bolts need to be clear of soil and standing water. Even columns embedded directly in concrete should not have their bases buried or submerged. Concrete footer caps should be elevated at least 6 ft. above existing grade, and should never be located in low areas frequently subjected to standing puddles.