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Wire sizing calculator NEC

The wire size calculator calculates the AWG wire size of electrical cables and wires according to the National Electricity Code (NEC) in the USA

Voltage (V)

Load
   cosΦ
Maximum volt drop (%)

Distance (m, ft)
 
Short circuit current and time
 kA    ms
Number of conductors

Insulation type

Number of parallel conductors

Installation


Load current 7 A
Recommended cable 1 x 12 AWG
NEC table TABLE 310.15(B)(16)
AWGSize mm2Rating AVolt drop %Fault rating kA
142.08020.03.743.5
123.31025.02.425.5
105.26135.01.438.7

See Also

Parameters:

Current rating:

Derating:

Voltage drop calculation:

\(V_{d1\phi}=\dfrac{I L (2 Z_c)}{1000}\)

where I is the load current, L is the distance, and \(Z_c\) is the cable impedance in O/km.

\(V_{d3\phi}=\dfrac{I L (\sqrt{3}Z_c)}{1000}\)

\(Z_c =\sqrt{R_c^2 + X_c^2}\)

where \(R_c\) is the resistance and \(X_c\) is the reactance. This method calculates the impedance for the worse case power factor, i.e. when the cable and load power factor is the same.

Short circuit calculation:

\(\bigg(\dfrac{I}{A}\bigg)^2 t = 0.0297 \log\bigg(\dfrac{T_2+234}{T_1+234}\bigg)\)

where: