All electrical installations and equipment shall be cleaned and inspected at intervals as experience has shown to be necessary. Any equipment or electrical installation known to be defective so as to endanger life or property shall be promptly repaired, permanently disconnected, or isolated until repairs can be made. Construction, repairs, additions, and changes to electrical equipment and conductors shall be made by qualified persons only.
Wis. Admin. Code Department of Safety and Professional Services SPS 316.010