NEC 2023 Voltage Drop Changes: What You Need to Know
A comprehensive look at how NEC 2023 addresses voltage drop requirements.
The NEC 2023 edition brings important clarifications to voltage drop recommendations that every electrical professional should understand. While voltage drop remains an informational note rather than a mandatory requirement, the updated language provides clearer guidance for designers and installers.
Key Changes in NEC 2023
The 2023 NEC maintains the fundamental voltage drop recommendations from previous editions but includes refined language that emphasizes the importance of voltage drop analysis for efficient electrical system operation. The core recommendations remain unchanged: 3% maximum for branch circuits, 3% for feeders, and 5% total from service entrance to the farthest outlet.
Section 210.19(A) Informational Note No. 4
"Conductors for branch circuits as defined in Article 100, sized to prevent a voltage drop exceeding 3 percent at the farthest outlet of power, heating, and lighting loads, or combinations of such loads, and where the maximum total voltage drop on both feeders and branch circuits to the farthest outlet does not exceed 5 percent, provide reasonable efficiency of operation."
Practical Implications for Designers
- EV Charging Growth: The explosion of EV charger installations creates many long-run branch circuits where voltage drop is the controlling design factor.
- Energy Efficiency Focus: With increasing emphasis on building energy performance, specifiers are more frequently requiring voltage drop analysis.
- Sensitive Electronics: Modern buildings contain more electronic loads sensitive to voltage quality.
Best Practices for NEC 2023 Compliance
Do
- • Calculate voltage drop for all circuits over 50 feet
- • Document calculations in design files
- • Consider 2% branch / 3% feeder for sensitive loads
- • Verify with field measurements post-installation
Avoid
- • Ignoring voltage drop because it's "just informational"
- • Using voltage drop as the only sizing criterion
- • Assuming 5% is acceptable for all applications
- • Forgetting to account for motor starting currents
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