Section 8. An appointing authority, with the approval of the administrator, may promote an employee in the official service from one title to the next higher title in the same series in the same departmental unit, subject to the following requirements: (a) such employee shall have been employed in such unit in such lower title as a permanent employee for three years or longer immediately preceding the request for approval of such promotion; (b) such employee is the first, second, or third ranking employee in length of service in such departmental unit who is willing to accept the promotion; and (c) such employee shall demonstrate, by the passing of an examination prescribed by the administrator, that he possesses the qualifications and abilities necessary to perform the duties of the higher title; provided that an employee in a departmental unit of a city, town or district who has been employed in such unit in a lower title as a permanent employee for not less than one year next preceding the date of such request may be promoted to the next higher title in the same series if there is no other employee in such lower title or any other lower title in such series who has also been so employed, and if such employee shall demonstrate, by the passing of an examination prescribed by the administrator, that he possesses the qualifications and abilities necessary to perform the duties of such higher title. The relative ranking of titles as next higher or lower shall be determined by the administrator.

In case of promotional appointments of more than one employee, the appointing authority may select from among the same number of employees with the greatest length of service as the number provided in the civil service rules governing appointments to fill more than one vacancy.

The effective date of a promotional appointment made pursuant to this section shall be the date on which the person promoted assumes the duties of the higher title, as certified by the appointing authority, following the approval of the promotion by the administrator.

The provisions of this section may be utilized to make a temporary promotional appointment to fill a temporary vacancy in a permanent position if the administrator is satisfied that such vacancy is likely to become permanent within a reasonable period of time. If a person has received such a promotional appointment, the administrator, upon the request of the appointing authority, may approve such promotional appointment on a permanent basis when the position to which the temporary promotional appointment has been made becomes permanently vacated.