I have always been taught for the past 30 years that you cannot use double pole (220/240V) breakers as single pole. When I moved into my newly built home, I ofcourse checked the checked the main panel. When I opened the panel I immediately noticed that there were several double pole breakers with single pole circuits. The "tie bar" was left intact on the breakers. I have been checking my NEC and cannot find the section that states that it cannot be done. Help!!!