Grounding wire size calculator
Related Calculators
Grounding Wire Size Calculator - complete guide
Table of Contents
Introduction
The grounding wire is a critical component of any electrical installation. Proper grounding ensures that fault currents safely travel to the earth, protecting both equipment and individuals.
Understanding how to select the correct wire gauge is essential. This calculator provides accurate recommendations for copper and aluminum conductors based on various electrical parameters.
Whether you are a professional electrician or a homeowner, using the right wire gauge for your grounding system guarantees optimal electrical safety.
Why Grounding Wires Are Important
Grounding wires prevent electrical shocks by providing a path for excess current to flow safely into the earth. This helps protect both people and sensitive electrical equipment.
Proper installation of grounding conductors reduces the risk of equipment damage during lightning strikes or short circuits. Always follow recommended guidelines.
Choosing the correct copper conductor or aluminum wire size is vital. Undersized wires can overheat, while oversized wires may be unnecessarily expensive.
Types of Calculations
This calculator supports three calculation types for grounding wires:
- By ampacity — select the current rating to determine wire size.
- By fault current and length — considers potential short-circuit currents and conductor distance.
- By breaker size — quick lookup based on the installed breaker rating.
Users can select their preferred calculation type, input values, and instantly receive recommended wire sizes in AWG and mm².
Ampacity Table
| Ampacity (A) | Copper AWG | Copper mm² | Aluminum AWG | Aluminum mm² | Recommended Usage | Notes |
|---|---|---|---|---|---|---|
| 15 | 14 | 2.08 | 12 | 3.31 | Lighting circuits | Residential standard |
| 20 | 12 | 3.31 | 10 | 5.26 | Small appliances | Kitchen outlets |
| 30 | 10 | 5.26 | 8 | 8.37 | Air conditioners | Residential & light commercial |
| 40 | 8 | 8.37 | 6 | 13.3 | Water heaters | Standard practice |
| 55 | 6 | 13.3 | 4 | 21.2 | HVAC | Commercial light |
| 70 | 4 | 21.2 | 2 | 33.6 | Industrial machinery | High demand |
| 95 | 2 | 33.6 | 1 | 42.4 | Large equipment | Ensure correct insulation |
Fault Current Table
| Fault Current (A) | Length (m) | Copper mm² | Aluminum mm² | Voltage Drop (V) | AWG | Recommended Use |
|---|---|---|---|---|---|---|
| 100 | 10 | 10 | 16 | 5 | 10 | Residential small circuit |
| 200 | 20 | 21 | 32 | 5 | 8 | Medium circuit |
| 300 | 30 | 31 | 50 | 5 | 6 | HVAC system |
| 400 | 40 | 42 | 67 | 5 | 4 | Industrial equipment |
| 500 | 50 | 53 | 85 | 5 | 2 | Large industrial |
| 600 | 60 | 64 | 107 | 5 | 1/0 | Heavy machinery |
| 700 | 70 | 76 | 128 | 5 | 2/0 | Industrial high load |
Breaker Size Table
| Breaker Size (A) | Copper AWG | Copper mm² | Aluminum AWG | Aluminum mm² | Application | Notes |
|---|---|---|---|---|---|---|
| 15 | 14 | 2.08 | 12 | 3.31 | Lighting circuits | Residential |
| 20 | 12 | 3.31 | 10 | 5.26 | Outlets | Kitchen & living |
| 30 | 10 | 5.26 | 8 | 8.37 | AC & small machines | Residential & commercial |
| 40 | 8 | 8.37 | 6 | 13.3 | Water heaters | Standard |
| 55 | 6 | 13.3 | 4 | 21.2 | HVAC | Commercial light |
| 70 | 4 | 21.2 | 2 | 33.6 | Industrial | High demand |
| 95 | 2 | 33.6 | 1 | 42.4 | Large machinery | Check insulation |
Calculation Examples
Example 1: A 20 A circuit with copper conductor → 12 AWG, 3.31 mm².
Example 2: Fault current 200 A over 20 m with aluminum → 32 mm², 8 AWG.
Example 3: Breaker 30 A with copper → 10 AWG, 5.26 mm².
Example 4: 50-foot copper wire for AC unit → ~8 AWG, 8.37 mm².
Example 5: Residential lighting 15 A → 14 AWG copper, 2.08 mm².
Calculation Formula
A = (I × L) / (K × Vd)
Where A = wire cross-sectional area (mm²), I = fault current (A), L = length (m), Vd = allowable voltage drop (V), K = conductivity constant (53 for copper, 32 for aluminum).