Whenever you shop for electrical wire, you will see that there are numbers of types and sizes from which you have to choose from. So different types of wire are made for different uses, but with any of these wire types knowing the right wire sizes or gauge, is key to making the right choices. Wire gauge refers to the physical size of the wire, rated with numerical designation that runs opposite to the diameter of the conductors . In other words, the smaller the wire gauge number, the larger the wire diameter.
Common sizes include 1.00 sq. mm, 1.50 sq. mm, 2.50 sq. mm, 4.00 sq. mm. The wire size shows how much current can safely pass through the wire. For standard non-metallic(NM) cable, these amperage capacities are
- 0.50 sq. mm : 4 amps
- 0.75 sq. mm : 8 amps
- 1.00 sq. mm : 12 amps
- 1.50 sq. mm : 16 amps
- 2.50 sq. mm : 22 amps
- 4.00 sq. mm : 29 amps
These ratings are for standard copper NM sheathed cable, but there are instances where these amperage ratings vary. Check all the wires and rates here
Stranded vs. Solid Wire
One more thing to keep in mind is to select the style of wire that best fits your needs. Some wire is stranded, while other wire consists of a solid copper conductor. In installations using metal conduit, the solid wire doesn’t always pull as easily if the conduit has a large number of bends. But solid wire is usually easier to secure under screw terminals, such as those found on standard switches and receptacles.
Why wire gauge is important?
Incase of overloading wire and overheating them, circuit breakers or fuses gives good protection but they are not much reliable and not a foolproof protection. Both circuit breakers and fuse are designed to sense current loads to “trip” or “blow” before the wires can overheat up to the danger point.
There is the potential for danger anytime a device or appliance tries to draw more power on a circuit than the wire gauge is rated for. For example, plugging a heater rated for 22 amps into a 16-amp circuit wired with 1.50 sq. mm wire poses a distinct danger.
Differently it will be very safe by plugging appliances with moderate electric load into circuit with heavier gauge and a higher amperage rating. So, for example, running a laptop computer with a very small amperage demand on a 22-amp circuit wired with 2.50 sq. mm wire is perfectly fine.
|Wire Use||Rated Amp capacity||Wire Gauge|
|Low-voltage lighting and lamp cords||12 amps||1.00 sq. mm|
|Light fixtures, lamps, lighting circuits||16 amps||1.50 sq. mm|
|Kitchen, bathroom, and outdoor receptacles (outlets);120-volt air conditioners||22 amps||2.50 sq. mm|
|Electric clothes dryers, 240-volt window air conditioners,electric water heaters||29 amps||4.00 sq. mm|
|Cooktops and ranges||37-51 amps||6 & 10 sq. mm|
|Electric furnaces, large electric heaters||68 amps||16.00 sq. mm|