What Is the DC Circuit Breaker & Wire Ampacity Sizing Calculator?
Low-voltage DC circuits (12V, 24V, 48V) require much thicker copper wires than 120V/240V AC circuits because high currents create severe resistance losses.
How Does the DC Circuit Breaker & Wire Ampacity Sizing Calculator Work?
Computes continuous current: I = Watts ÷ Volts.
Applies the NEC 125% continuous duty rule to select standard overcurrent protective device (OCPD) breaker ratings.
Evaluates copper circular mil cross-sectional area to ensure circuit voltage drop stays below 3.0%.
DC Circuit Breaker & Wire Ampacity Sizing Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
NEC continuous load protection sizing coupled with copper conductor circular mil resistivity (K = 12.9 ohms-cmil/ft).
How to Use the DC Circuit Breaker & Wire Ampacity Sizing Calculator
- Enter total load wattage.
- Enter battery system voltage.
- Enter one-way wire distance in feet.
Step-by-Step Example Calculation
1,200W Load on a 24V System over a 25 ft Run
Input Values:
Understanding Your Result
Recommends minimum standard AWG copper wire gauge and DC-rated breaker size.
Factors That Affect the Result
- Conductor insulation temperature rating (60°C, 75°C, or 90°C) and engine bay ambient heat deratings.
When Should You Use This Calculator?
- Wiring campervan conversions, solar battery inverters, trolling motors, and boat electrical panels.
Assumptions & Limitations
- Assumes pure copper stranded conductor at 75°C rating.
Frequently Asked Questions
Calculation Accuracy & Reference Note
National Electrical Code (NEC Table 310.16) and ABYC marine standards.