Grounding Wire Size Calculator

The ElectriCalc Pro electrical calculator easily calculates grounding conductor wire sizes. You can use single or multiple service entrance conductors to find the grounding electrode conductor for AC systems.

When using multiple conductors, the ElectriCalc Pro uses the equivalent Circular Mils to find the grounding electrode conductor based on NEC® table 250-66

How To Find Grounding Conductor Wire Size

The example below shows how to calculate the ground wire size required when 2/0 is the largest 3-phase 75° copper service entrance conductor being used. It also shows how to find the equivalent aluminum wire size, and equivalent Circular Mils.

Steps Keystrokes Display
1: Clear calculator On/C On/C
3 PH
2: Set to 3-phase Set 3
30 75
Cu
3 PH
3: Set to 75° C Set 7
30 75
Cu
3 PH
4: Enter wire size (12) 1 2 WireSz
AWG
30 75
Cu
12 CU
WIRE SIZE
5: Find ground wire size Grnd
GRND
30 75
Cu
8 CU
WIRE SIZE
6: Find aluminum ground wire size Grnd
GRND
30 75
Cu
6 AL
WIRE SIZE
7: Find Circular Mils Grnd
CMIL
30 75
Cu
6,530.
WIRE
8: Display NEC Table Grnd
NEC
30 75
Cu
250.66

Note that wire size can also be entered in Circular Mils (e.g., 1 3 3 1 0 0 WireSz enters 133,100 CMILs and displays 00 AWG Wire Size).



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