Because of the power it needs, a dishwasher should always have its own circuit, separate from the two individual appliance circuits that are often positioned above your countertop. Although you may see dishwashers connected to existing wiring in older homes, the problem really lies in the breaker or fuse. In older homes, the breaker or fuse may not be as functional as current ones. Thus, if your dishwasher overloads the circuit, the older breaker or fuse may not pop, and your wiring will heat up to dangerous levels.
Dishwashers run on 115-volt or 120-volt power. The dishwasher circuit should be a 125-volt, 15-amp circuit. You can feed the dishwasher a 20-amp circuit with a ground. This will mean running cable from the breaker box to the dishwasher. You’ll need to drill a hole into the cabinet box through drywall for a cable or through the floor if the cable will come up from below. You will need to install a breaker in a free space, attach the wires and run the cable to the dishwasher.