This question reminded me that when we bought our house, I found the previous owner had taken the dryer's 220v circuit and continued half of it from the 220v outlet to make a 110v circuit for the rest of the garage.
The 220v outlet still powered the dryer.
Even as a new naive home owner this struck me as probably incorrect and had it fixed when we upgraded the panel.
Can you explain the specific reasons why this was bad – and what code it breaks?
Best Answer
Other than what @ArchonOSX has pointed out as code requirements. Adding receptacles added on to a dryer circuit is just not considered good electrical practice.
Consider how you started your question "previous owner had taken the dryer's 220v circuit". You called it the Dryer's circuit. That means the original circuit installed is a specific circuit designed to service a dryer, not a dryer and anything else we can stick on it. Depending on what you put on the circuit, it could create an imbalance (impedance) between the two phases and directly affect the life of both the circuit and piece of equipment. I also have a question about what your overcurrent protection looks like since most branch wire is protected by 15A and 20A breakers. To add devices that should be protected by these breakers to be attached to a 30A breaker would they have to meet a whole new set of requirements. By the way if you have a problem with your dryer and call for warranty repair and the service representative sees the attached receptacles. He would be in his right to void the warranty.
Some could make an argument that it might not affect the dryer but we don't design circuits around what they might do. We design circuits that we know work.
So best advice install dryer circuits for dryers and add general power circuits for general power.
Hope this helps and stay safe.