If a regular member of a zoning board of appeals is absent, he may designate an alternate from the panel of alternates to act in his place. If he fails to make such designation or if he is disqualified, the chairman of the board shall designate an alternate from such panel, choosing alternates in rotation so that they shall act as nearly equal a number of times as possible. If any alternate is not available in accordance with such rotation, such fact shall be recorded in the minutes of the meeting.