A miniature circuit breaker, or MCB, functions similarly to a normal electrical circuit breaker but is much smaller in size. Using electronic circuitry to achieve its small overall size, an MCB takes up half the space of a normal circuit breaker inside the electrical panel. MCBs prevent too much current from flowing through electrical wiring by tripping, thus preventing damage to the circuit and to the appliance using the electricity.
Open the electrical panel inside your home, and turn off the main circuit breaker inside the panel. Unscrew the panel board cover with a screwdriver, and locate an empty slot on the panel board. Knock out an access hole on the service panel with a hammer and screw to allow the cable for the new circuit.
Run the wires coming from the receptacle, switch or appliance -- in case the appliance is hard-wired to the circuit -- to the electrical panel. Slip the wires through the hole punched out in Step 1, and pull the wires from inside the panel.
Divert the black wire to the base of the miniature circuit breaker, divert the white wire to the neutral bar and divert the green or bare wire to the ground bar. Strip off 1/2 inch of insulation from the tip of each wire using a wire stripper.
Plug the miniature circuit breaker into the vacant slot on the panel board. Insert the tip of the black wire into the slot beneath the terminal screw at the end of the breaker, and tighten the terminal screw to secure the connection. Attach the green wire to the terminal screw on the ground bar, and attach the white wire to the terminal screw on the neutral bar.
Replace the cover of the electrical panel. Switch on the main circuit breaker, and flip the switch of the miniature circuit breaker to its "On" position. Turn on the appliance or light connected to the circuit breaker to test the connection.
Working with electricity is dangerous; it can cause damage to property, injury or even death. Never attempt to perform any electrical task if you do not possess qualified training and experience. Working with electrical circuits requires knowledge of existing national and local electrical codes. Ignorance of these codes can lead to a fire. Electrical loads can only use up to 80 per cent of a circuit's total amperage.