The cross-section of the wire from the machine to the junction box is determined by several factors:
Chain load:
– Calculate the maximum power (in watts) consumed by all devices that will be connected to the circuit.
– Divide the power by the voltage (usually 220V in residential applications) to obtain the current (in amps).
Permissible current load of the wire:
– Use the current carrying capacity table to select a wire with a cross-section sufficient to carry current safely.
Wire length:
– Longer wires have more resistance, resulting in a voltage drop. Select a wire size that compensates for the voltage drop over the length of the wire.
Wire type:
– Copper wires are usually used because they have lower resistance than aluminum wires.
The following are recommended wire sizes for general loads:
* Lighting: 1.5mm?
*Sockets: 2.5mm?
* Air conditioning: 4 mm? and more (depending on power)
* Oven: 6 mm? and more (depending on power)
Example:
If the total power of the devices in the circuit is 2000 W, the current will be equal to 9.1 A. When choosing a wire from the table of permissible current loads, you can choose a copper wire with a cross-section of 1.5 mm?, which is designed for a current of up to 15 A.
It is always better to choose a wire with a slightly larger gauge to provide a margin of safety and prevent overheating.