(Iz) = current carryng capacity of the cable where it is installed. (It) = tabulated current for a single circuit at ambient temp of 30°

(Ib) = the actual current to be carried. (In) = is the Circuit Breaker rating in Amps.(I2) = the current at which the CB opens.

(Ca) = correction factor for Ambient temp. (Cg) = correction factor for grouping. (Ci) = correction factor for thermal insulation.

One method to determine the Potential short circuit current if you do not have a Loop Impedance Tester.

Find the volt drop of the system V1-V2 Divided by the Load gives Zs. Where V1 is the open circuit voltage,

V2 is the voltage under load and load is the amperage of the system.

IE: (V1)240 - (V2)238 = 2 divided by the Load 40Amps = 0.05 Ω.

Then PSC = System voltage (Uo) / (Zs) 240 ÷ 0.05 = 4800 Amp.

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