All electrical equipment installed or used shall be in conformity with the provisions of this article, the statutes of the state and any orders, rules and regulations issued by authority thereof, and with approved electrical standards for safety to persons or to property. Unless by this article, by a statute of the state, or any orders, rules or regulations issued by authority thereof, a specific type or class of electrical equipment is disapproved for installation and use, conformity with the standards of Underwriter’s Laboratories, Inc., shall be prima facie evidence of conformity with approved standards for safety to persons or to property.
(`90 Code, § 4-27)