Conductor size

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A comparison of standard mm² conductor sizes and standard AWG conductor sizes. AWG decreases as conductor size increases, mm² increases as conductor size increases.

Conductors come in standard sizes depending upon the location. The proper conductor size for a particular circuit depends on two important considerations:

  1. The amount of current that they can safely carry given the conditions in which they will be used. The conditions of use that must be considered include: the number of wires in the conduit, the maximum ambient temperature, and the appropriate overcurrent protectiond device size.
  2. The amount of voltage that will be lost under operation, which is called voltage drop

The wires for an off-grid system must will be sized and selected based upon the load evaluation and the physical evaluation for a particular site. This process must be done in conjunction with the sizing and selection of an overcurrent protection device for the circuit - see Dimensionamiento y selección de cables, protección contra sobrecorrientes y medios de desconexión for more information.

The two most common standards for conductor size are American Wire Gauge (AWG) and mm². These two systems are not directly equivalent. The table below shows conductor sizes in AWG and mm² with the ampacity (maximum current) rating of depending upon its temperature rating of the conductor in °C. This chart assumes that there are are 1-3 copper conductors in conduit with a 30°C ambient temperature.[1] These values must be adjusted for the actual conditions of use of the conductor.

60°C 75°C 90°C
AWG size Area (mm²) Metric equivalent (mm²) Types TW, UF Types RHW, THHW, THW, THWN, XHHW, USE, ZW Types TBS, SA, SIS, FEP, FEPB, MI, RHH, RHW-2, THHN, THHW, THW-2, THWN-2, USE-2, XHH, XHHW, XHHW-2, ZW-2
14 2.08 mm² 2.5 mm² 15 A 20 A 25 A
12 3.31 mm² 4 mm² 20 A 25 A 30 A
10 5.26 mm² 6 mm² 30 A 35 A 40 A
8 8.37 mm² 10 mm² 40 A 50 A 55 A
6 13.3 mm² 16 mm² 55 A 65 A 75 A
4 21.2 mm² 25 mm² 70 A 85 A 95 A
3 26.7 mm² 85 A 100 A 110 A
2 33.6 mm² 35 mm² 95 A 115 A 130 A
1 42.4 mm² 50 mm² 110 A 130 A 150 A
1/0 53.5 mm² 125 A 150 A 170 A
2/0 67.4 mm² 70 mm² 145 A 175 A 195 A
3/0 85 mm² 95 mm² 165 A 200 A 225 A
4/0 107 mm² 120 mm² 195 A 230 A 260 A

Cable size

Cables are typically designed to contain all of the conductors that are needed for a particular circuit. Therefore there are many different configurations of cable that vary based upon the size of the conductors, the number of conductors, and the color of the conductors. Cables will be labeled with the size of the current carrying conductors and the quantity. For example a cable with three 12 AWG conductors will be labeled "12/3". A cable with three 2.5mm² conductors will be labeled "2.5mm²/3" or "2.5mm² three core". Equipment grounding conductors (EGCs) are generally excluded from the count of conductors and should be specified separately.

Notes/references

  1. NFPA 70 - National Electrical Code 2020: Table 310.15(B)(16)