As Sean notes above there are potential problems to adding additional supply lines to your system, and is why I always advocate simulating a proposed additional line(s) setup for those who need/or want to try. There's even more potential problems with AGG's setup.
For starters it violates the National Electric Code which requires seperate a neutral (white) wire to the neutral side and seperate ground (usually bare or green) to the ground connection of a 115 volt outlet. The reason for this is to avoid the dangerous potential of a floating ground.
AGG, if your lines breaker is a double wide unit with a common lever, the two lines are most likely out of phase with each other. That's the normal way to get 230 volts in a common residential system. Don't even think of putting one of these lines on a different breaker (to create a common phase supply). You risk creating an extremely dangerous situation where 40 amps can travel thru a very undersized wire.
Like other posters to power related postings on this site: If you are not clear of the code requirements for a safe installation. Hire a licensed electrician for his knowledge.
For starters it violates the National Electric Code which requires seperate a neutral (white) wire to the neutral side and seperate ground (usually bare or green) to the ground connection of a 115 volt outlet. The reason for this is to avoid the dangerous potential of a floating ground.
AGG, if your lines breaker is a double wide unit with a common lever, the two lines are most likely out of phase with each other. That's the normal way to get 230 volts in a common residential system. Don't even think of putting one of these lines on a different breaker (to create a common phase supply). You risk creating an extremely dangerous situation where 40 amps can travel thru a very undersized wire.
Like other posters to power related postings on this site: If you are not clear of the code requirements for a safe installation. Hire a licensed electrician for his knowledge.