In case you don’t have the information here are the 2 McConnell households in Ballynadrentagh in the 1851 census. The first seems likely to be your immediate line. The second is proably also connected:
http://www.census.nationalarchives.ie/pages/1851/Antrim/Lower_Massereene/Killead/Ballynadrentagh/10/
http://www.census.nationalarchives.ie/pages/1851/Antrim/Lower_Massereene/Killead/Ballynadrentagh/16/