(a) There shall be no communication, direct or indirect, while a proceeding is pending regarding the merits of any issue in the proceeding, between the presiding officer and the agency head or other person or body to which the power to hear or decide in the proceeding is delegated.
(b) This section does not apply where the agency head or other person or body to which the power to hear or decide in the proceeding is delegated serves as both presiding officer and agency head, or where the presiding officer does not issue a decision in the proceeding.