(1) Where, and only where, the submission expressly so provides may an umpire be appointed by the arbitrators; the same to be done by them in writing.
(2) The umpire shall sit with the original arbitrators upon the hearing; if testimony has been taken before the umpire's appointment, the matter must be reheard unless a rehearing is waived in the original submission or by subsequent written consent of the parties.
(3) One (1) or more points in dispute may be referred to an umpire.