Any change in a nonconforming use shall comply with the applicable regulations of this Planning and Zoning Code. A change in ownership or occupancy shall not in itself constitute a change of use. When a previously nonconforming use has been changed to a conforming use, such nonconforming use shall not thereafter be changed to a nonconforming use. A nonconforming use may not be changed, except in accordance with the following provisions:
(a) A nonconforming use that is subject to termination in accordance with the requirements of this Code shall not be substituted for another nonconforming use.
(b) A nonconforming use of land involving a building or structure, where the assessed value of the buildings or structures is more than twenty thousand dollars ($20,000), shall not be changed to another nonconforming use.
(c) A nonconforming retail use located within a Residential District may be changed to a residential use, except a multiple-family use, unless such use is located within a district permitting multiple-family uses.
(d) A nonconforming manufacturing use located within a Residential District may be changed to a residential use, except a multiple-family use, unless such use is located within a district permitting multiple-family uses.
(e) A nonconforming retail or manufacturing use located within a Commercial District may be changed to any use permitted in that particular zoning district or in the next most restrictive Commercial District from that in which the nonconforming use is located.
(f) The change of nonconforming uses as provided in this section shall not extend the time for the termination of nonconforming uses.