(a) Except as provided in subdivisions (b) and (c) and in Rules 400.1 and 1930.4, original process shall be served within the Commonwealth only by the sheriff.(b) In addition to service by the sheriff, original process may be served also by a competent adult in the following actions:
(1) civil action in which the complaint includes a request for injunctive relief under Rule 1531, perpetuation of testimony under Rule 1532 or appointment of a receiver under Rule 1533,(2) partition, and(3) declaratory judgment when declaratory relief is the only relief sought.(c) When the sheriff is a party to the action, original process shall be served by the coroner or other officer authorized by law to perform the duties of coroner. (d) If service is to be made by the sheriff in a county other than the county in which the action was commenced, the sheriff of the county where service may be made shall be deputized for that purpose by the sheriff of the county where the action was commenced.