Last updated: October 4, 2026
NEC 215.2 requires feeder conductors to have an ampacity not less than the calculated load they serve — sized at 125% of the continuous load plus the non-continuous load — with voltage drop recommended to stay under 3% on the feeder and 5% total. Those two numbers decide most feeder sizing questions on commercial jobs.
Feeder conductors are the lifeline of commercial electrical systems, carrying power from service equipment to distribution panels across a facility, and feeder sizing mistakes are one of the top reasons projects get flagged during inspections. This guide breaks down the NEC 215.2 requirements, the logic behind load and voltage drop calculations, and field-level tips for passing inspection the first time. For broader context, review our guide on NEC Services and Feeders first.
What does NEC 215.2 require?
NEC 215.2 sets three sizing requirements for feeders: minimum ampacity for the load, a minimum size for safe overcurrent protection, and a recommended voltage drop limit.
NEC 215.2(A)(1) — Feeder sizing by load.
- Feeder conductors must have an ampacity not less than the calculated load served.
- The load is determined per Article 220, which covers general load calculations for lighting, receptacles, HVAC, and equipment.
- Where continuous loads are supplied, feeders must be sized at 125% of the continuous load plus the non-continuous load.
NEC 215.2(A)(3) — Minimum size.
- Feeders must be large enough to allow safe overcurrent protection — for example, conductors must match the OCPD rating per NEC 240.4.
NEC 215.2(A)(4) — Voltage drop recommendation.
- Not an enforceable requirement, but an Informational Note (formerly FPN) strongly recommends limiting voltage drop to 3% on any feeder and 5% total (feeder plus branch circuit combined).
- Contractors often overlook this, but inspectors use it as a benchmark of quality workmanship.
How do you calculate the feeder load under Article 220?
The feeder load is the sum of the Article 220 component loads, with demand factors applied where allowed:
- General lighting load: based on building occupancy type (NEC 220.12) — see our guide to NEC 220.42 lighting load calculations.
- Receptacle loads: calculated at not less than 180 VA per receptacle (NEC 220.14).
- HVAC and motors: largest motor load plus 25% (NEC 430.24).
- Demand factors: apply demand factors where allowed to avoid oversizing.
👉 Correct load calculations are the foundation of feeder sizing and compliance with NEC 215.2.
How much voltage drop is acceptable on a feeder?
Keep voltage drop under 3% on the feeder and 5% total (feeder plus branch circuit). The limit is an Informational Note rather than an enforceable rule, but it is the benchmark inspectors and engineers use — and voltage drop is a real-world performance issue. Too much drop causes dimming lights, reduced motor torque, heat buildup in equipment, and energy waste.
Practical example: a 200-amp feeder runs 250 feet to a subpanel. Aluminum conductors may produce excessive drop unless upsized; copper costs more upfront but avoids long-term headaches.
Contractors should calculate voltage drop using NEC Chapter 9 tables or software tools, then upsize feeders as needed. For more feeder-specific considerations, see NEC Services and Feeders.
What are the most common NEC 215.2 mistakes?
- Ignoring continuous load adjustments → undersized feeders.
- Failing to consider future expansion → feeders maxed out too soon.
- Misusing demand factors → oversimplified calculations.
- Skipping voltage drop analysis → failed performance under load.
- Mismatched OCPD ratings → inspectors red-tagging installations.
What are the labeling requirements for feeders?
NEC 110.22 and 215.5 require that feeder disconnects and panels be clearly identified. On large commercial jobs, improper labeling can be as costly as improper sizing.
✅ At Print Pro, we provide custom NEC-compliant labels for feeder panels, disconnects, and distribution equipment, ensuring projects pass inspection without delays.
How do you size feeders that pass inspection?
- Always size feeders at 125% of continuous load — don't cut corners.
- Run voltage drop calculations for long runs, even when not required.
- Upsize conductors when running aluminum, especially for motors.
- Factor in future load growth when designing feeders.
- Pre-label feeder disconnects and panels to save time during final inspection.
NEC 215.2 frequently asked questions
What ampacity must a feeder conductor have?
Not less than the calculated load it serves, determined per Article 220. Where continuous loads are supplied, the feeder must be sized at 125% of the continuous load plus the non-continuous load.
Is the NEC voltage drop limit enforceable?
No. The 3% feeder / 5% total guidance in NEC 215.2 is an Informational Note, not an enforceable requirement — but inspectors treat it as the benchmark of quality workmanship, and excessive drop causes real performance problems.
Which loads go into a feeder calculation?
General lighting by occupancy (NEC 220.12), receptacles at not less than 180 VA each (NEC 220.14), and HVAC/motors at the largest motor load plus 25% (NEC 430.24), with demand factors applied where allowed.
Do feeder disconnects and panels need labels?
Yes. NEC 110.22 and 215.5 require feeder disconnects and panels to be clearly identified, and on large commercial jobs improper labeling can be as costly at inspection as improper sizing.
Conclusion
NEC 215.2 ensures feeder conductors are properly sized to handle demand and protect against hazards. Accurate load calculations, voltage drop analysis, and NEC-compliant labels save time, avoid red tags, and deliver safer, more efficient installations.
To see how feeders fit into the bigger NEC picture, read our detailed guide on Services and Feeders.
👉 Ready to pass inspections with ease? Order feeder panel and disconnect labels at PrintProAZ.com.