When working with electrical cables, the markings on a cable sheath contain a set of two digits separated by either “-” or “/”, such as 12-2, 12/2, 14-2, 14/2 or similar combinations, the number on the left if punctuated, the AWG meter indicates the conductors inside the cable while the one on the right indicates how many conductors are inside the cable, but excluding the ground wire. Figures 1a, 1b and 1c show these markings for three different types of cables.
AWG Cable Size –The wire size or AWG meter number has nothing to do with the amount of voltage applied through it, but indicates the maximum amplifiers or current that can be sent to it without heating, but there is another marking on the cable sheath, however, to indicate the maximum voltage which cable is safe to use – usually 300V or 600V. So if you connect a line with 120 volt sockets that require 20 amp distribution – around the kitchen counter, for example where many appliances can run at the same time during high season – you need 12/2 cables and 20 amp rated sockets — Not all outlets are created equal. The 12 AWG cables can withstand the current having a larger diameter, where the 14 AWG cable which is smaller will heat up over 15 amps and cause the cable or a 15 A socket to melt or catch fire.
Amplifier by wire size—Note that the number of AWG decreases, the wire diameter increases.
14 AWG leaders can handle a load of no more than 15 amps.
12 AWG measuring cables can withstand up to 20 amps at 120 volts if a lead is white for the neutral return lead. If neither of the two wires is white, it is black. red, blue or other color, each should carry one side of the 240 volt line. So even with just two wires, beware if you come across a circuit with a supply that does not have a white neutral gift.
10 AWG leaders is for loads up to 30 amps, usually at 240 volts. If the appliances they supply have internal circuits that run on 120 volts – light bulbs or controls – 10/3 cables with a white wire should be used, but if 120 volts are not needed, a 10/2 cable would be ideal and cheaper.
8 AWG measuring cables can handle up to 45 amps. Whether it will be 8/2 or 8/3 here again, the same recommendations follow as above.
A 6 AWG cable capable of handling 60 amps is better suited for feeding a sub-panel, a series, a double oven, depending on the current indicated on the device. For any of these situations, it should be a 6/3 cable to also supply 120 volts.
Number of leaders –As shown in Figures 1a, b, & c, there is always the number to the right of the AWG cable size that indicates how many conductors are in a cable. This number of conductors does not include the ground wire, which is an additional wire with the sole purpose of providing a common ground reference to the house’s electrical.
Most of the wires needed for a house are Romex 14/2 and 12/2 for the 120 volt circuits. For the load of 240 volts, however, it depends on the load cycle whether it requires a 12/2, 10/2, 8/2 or a 12/3, 10/3 or 8/3 cable.
A 14/3 and 12/3 cables have a black, a white and another colored cable (red, blue or other colors) for a more specialized use in hard line smoke and CO detectors, with the extra line that feeds the signal from a triggered alarm to all other alarms around the house.
Another use of a 14/3 cable is to connect a three-way switch where two different switches can activate the same luminaire in a room. The third wire, called the “traveler”, is used to ensure that there is always voltage at one or the other switch to power the lamp.
“G”, “w / G” or “with ground” markings –on the cable sheath the ground wire is mentioned but is not always used.
Absence of a white neutral wire –Sometimes there are indications on the jacket markings that limit the voltage a cable should carry. If we look at Figure 2, for example, the marking “2” follows another marking that indicates “RED-BLACK” which is the color of the two threads. Knowing that a neutral “white” wire is required for the return path when connecting a 120 volt circuit, such cables should only be used for 240 volts, as colored wires are always for hot power lines.
“NM” or “Romex” markings—The type of cable to be used around the homes is normally NM (meaning non-metallic) and is called and marked as Romex. Figures 1a and 1b are both NM or Romex cables (Figure 3).
“NMD” or “NMD90” markings –The addition of the letter “D” to the NM mark refers only to the use of that cable in dry places and in addition the figure “90” refers to its calorific value at 90 ° C.
“CU” or “AL” marks –sometimes spelled out completely because COPPER or ALUMINUM refers to the material with which the threads are made (Figure 4).
“U”, “UF” and “UF-Sunlight Resistant” markings –Sometimes when a supply from the house’s electrical panel is connected to an external load, such as an external floor lamp, a pump, the exterior or an adjacent structure, a UF cable (underground feeder shown in Figure 1c) is used if it is to be exposed to moisture. or water, and for that reason should always be connected via a GFCI switch. The UF markings sometimes include “Sunlight resistant”.
A “B” or “-B” marking –can be included after the NM and UF cable markings instead of “D” to indicate a higher calorific value of 194 ° Fahrenheit.
Date or year marking—also complements the mantle to indicate the date of its production.
So in the end, just understand what the coding says.