Electricity enters a home via a 220v cable into the distribution board that contains circuit breakers (or fuses in older houses). These circuit breakers divert the electricity along wires running in conduits in the walls and roof, forming separate circuits around a house which deliver electricity to all the switches and power points. A building has multiple circuits to help the electrical current stay small, reducing the risk of overloading the circuits. Some appliances, such as a stove, dishwasher, air-conditioner/ heater or dryer, draw more power than a light point and therefore may require their own circuit.
It is important that the correct size of wire or cable is used for the maximum potential load on a circuit.
The following specifications may be used for guidance:
- 1 or 1.5 mm² for lighting, depending how many fittings are connected;
- 2.5 mm² for power circuits and ring mains, again depending on how many socket outlets are connected to the circuit and their application;
- 4 or 6 or 10 mm² for cookers, water heaters and air-conditioning, depending on current demand and output temperatures.
To work out how many watts an appliance is drawing, check the voltage and the amps of the appliance.
Therefore: 1 Amp at 12 volts = 12 watts.
- 1 Amp at 120 volts =120 watts.
Therefore: A 1200 watt hairdryer at 120 volts draws 10 amps (1200/120 = 10).