NEC 215.1 + 215.3 — Feeder Overcurrent Protection

What 215.1 (scope) and 215.3 (feeder overcurrent protection) actually say — verbatim 2017, 2020, and 2023 — the 125%-of-continuous-load OCPD floor, the 100%-listed-assembly exception, how 240.4 and Table 240.6(A) turn that floor into a real breaker, and the edition history that deleted Exception No. 2 and moved over-1000 V feeders to Article 235. Five worked examples, every number computed by the shipped calculator core. Last updated 2026-09-04 (written for PanelWright v1.16).

What 215.3 is (and the one mix-up to avoid)

215.3 answers one question: what is the minimum rating of the overcurrent device that protects the feeder? That is all it does. It is the device rule, not the conductor rule. The conductor side is 215.2 — the larger-of (a)/(b) ampacity rule with the 125% continuous multiplier and the temperature-column trap — and it gets its own treatment in the NEC 215.2 feeder ampacity article →.

Because the two rules carry the same 125% language, they are constantly confused in the field: 215.3 sizes the breaker; 215.2 sizes the wire. Run them in parallel and quote both — "feeder OCPD 100 A per 215.3, conductors 3 AWG Cu at 75 °C per 215.2." This article covers 215.1 (what the article covers) and 215.3 (the OCPD floor) in full, across three editions, because 215.3 is where the interesting edition history lives.

215.1 — Scope: what Article 215 covers

The 2023 NEC changed the scope sentence — the over-1000 V feeders left the article:

Two things to take from 215.1:

• Article 215 is the whole feeder package — installation, overcurrent protection, minimum size, ampacity. 215.3 is the overcurrent slice of it.
• The electrolytic-cell exception (668.3(C)(1) and (C)(4)) carves out cell-line conductors: they are exempt from Articles 110, 210, 215, 220, and 225, and cell process power circuits from Article 240. Niche, but it is the only thing in 215.1's exception list in every edition on disk (2017 and 2020).
• Edition boundary: in 2017/2020 the article covers feeders at all voltages (215.2 splits into (A) not more than 600 V [2017] / 1000 V [2020] and (B) over 600 V [2017] / over 1000 V [2020]). In 2023, 215.1 itself draws the line at 1000 V ac / 1500 V dc and points over-1000 V feeders to Article 235.

215.3 — the OCPD rule, verbatim, three editions

2020 and 2023 (identical)

Three rules in two sentences:

1. Hand-off: feeder OCPD follows Part I of Article 240 — the general OCPD requirements (location, listing, protection of conductors per 240.4, standard ratings per 240.6(A)). For a feeder ≤1000 V nominal, Part I of Article 240 is the whole relevant rule set in every edition on disk.
2. The floor: where the feeder carries continuous loads, OCPD rating ≥ noncontinuous + 125% × continuous. Note this is a minimum — a bigger standard size is always permitted as long as the conductors are protected per 240.4.
3. The exception: if the assembly — including the OCPDs themselves — is listed for operation at 100% of its rating, the floor drops to the plain sum (continuous + noncontinuous). The listing must cover the whole assembly, not just the conductors.

2017 (the edition with the deleted exception)

Exception No. 2 is the part that mattered for 600 V systems: it routed mid-voltage feeders to Parts I–VII of Article 240 and the >1000 V feeders to Part IX ("Overcurrent Protection over 1000 Volts, Nominal" — verified in the 2017 TOC and Article 240 part headings on disk).

One more piece of the 2017 wording, because the 100% exception has a conductor-side twin in 215.2(A)(1) — the ampacity rule that EX2 relies on (2017 text on disk, verbatim):

The edition history, verified line by line

Why the 2020 deletion? The AJB 2020 Code Change Analysis (Paul W. Abernathy, "Changes in the 2020 NEC," on disk) is explicit about 215.3: "While there were no significant changes to 215.3 Overcurrent Protection itself, I did want to bring the code user's attention to the removal of Exception 2 … So just to clear that exception is deleted for the 2020 NEC but I just wanted to let you know. The real reason for the deletion is that finally all 600-volt statements have been increased to 1000 volts, so it made the exception irrelevant in the eyes of the CMP." (The newsletter's own quotation of the deleted text — "Parts I through VIII … Part X" — carries two off-by-one part numbers versus the actual 2017 NEC on disk, which says Parts I through VII and Part IX; the deletion itself is confirmed against both the 2017 full text and the 2020 full text on disk.)

The same 600 V→1000 V migration is visible in 215.2 on disk: 2017's "(A) Feeders Not More Than 600 Volts … (B) Feeders over 600 Volts" becomes 2020's "(A) Feeders Not More Than 1000 Volts … (B) Feeders over 1000 Volts." The 2023 NEC then completes the move by pulling the over-1000 V content entirely out of Article 215: 215.1 draws the line at 1000 V ac / 1500 V dc and points over-1000 V feeders to Article 235 Part III, and 235.202 carries the former 215.2(B) transformer-nameplate-sum and supervised-installation rules essentially intact. Meanwhile Article 240 Part IX (the old home of over-1000 V OCPD) is dropped and its subject moves to the new Article 245.

Practical consequence: a 2017 design note that cites "215.3 Exception No. 2 → Article 240 Part IX" for a 600–1000 V feeder is dead in the 2020/2023 codes (the exception is deleted). For a genuinely >1000 V feeder, the 2020 code still keeps the OCPD content in Article 240 Part IX (transitional), but in 2023 the over-1000 V feeder OCPD device requirements are in the new Article 245, with 235.203 as the one-line feeder-OCPD pointer and 235.202 as the ampacity rule.

The interplay: 215.3 floor → 240.6(A) list → 240.4 protection

215.3 gives a number (the minimum OCPD rating). Three more rules turn it into an installed device:

1. 240.6(A) — standard ratings. The OCPD rating must be a standard ampere rating: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, 6000 A (2017/2020; the 2023 NEC prepends 10 A). Full treatment in the NEC 240.6 standard ampere ratings article →.
2. 240.4 — conductor protection. The conductors the OCPD protects must have ampacity at least equal to the OCPD rating — "unless otherwise permitted or required in 240.4(A) through (H)" (2023 text; the 2017/2020 list ran (A) through (G)).
3. 240.4(B) — the next-standard-size allowance. Where the required ampacity does not correspond to a standard rating, the next higher standard size is permitted, provided (1) the conductors are not part of a branch circuit supplying more than one receptacle for cord-and-plug-connected portable loads (feeders always pass this), (2) the ampacity does not correspond to a standard rating without overload trip adjustments above its rating, and (3) the next higher standard rating does not exceed 800 A. Verbatim 2023 text:

And the other side of the 800 A wall — where the allowance stops working entirely (240.4(C), verbatim 2023):

This is where 215.3's "minimum" language and 240.4's conductor protection meet: the OCPD must be at least the 215.3 floor, and the conductors must protect against that OCPD — and 240.4(B) is what lets a feeder OCPD sit one standard size above its conductors' ampacity (the EX4 case below).

Worked examples (all computed by the shipped core under node)

Every number below is produced by the shipped cores in app.js (reqBreakerA(), nextStdBreaker(), pickConductor31016(), node-invoked this session) and is asserted in the public test suite (test/run_tests.js in the public repo). Table 310.16 values are base values: 30 °C ambient, ≤3 current-carrying conductors — apply 310.15 ambient-temperature and conductor-count correction yourself for other conditions (the Table 310.16 article → covers the table; the conductor-sizing article → covers the corrections).

EX1 — 25 A noncontinuous + 60 A continuous, 75 °C terminations

The standard path through 215.3:

A clean landing: 100 A is both the 215.3 floor and a standard rating, and 3 AWG Cu at 75 °C (100 A) exactly matches it — no 240.4(B) allowance needed.

EX2 — same load, assembly listed for 100% operation

With the 215.3 exception (and its twin, 215.2(A)(1) Exception No. 1, which runs the same 100% language for ampacity):

Same load, one size of breaker and one size of wire smaller — if the assembly (including the OCPDs) is actually listed for 100% operation. Check the listing; the exception does not create the capability, it only removes the 125% margin where the listing already provides it. Note the 90 A OCPD now sits one standard size above the 85 A conductors (85 A is not a standard rating, and 90 A ≤ 800 A), so this path leans on 240.4(B) for the OCPD-to-conductor step — the same allowance EX4 relies on at full scale.

EX3 — 125 A noncontinuous + 40 A continuous

175 A is a standard rating (240.6(A) — note it is NOT one of the 210.18 multioutlet branch-circuit ratings; see the 210.18 article → for the two-list trap), and 2/0 AWG Cu at 75 °C (175 A) matches exactly. The 100% exception would give the same 175 A OCPD here (125 + 40 = 165 → next standard is still 175 A), so for this load split the exception buys nothing.

EX4 — 5 A noncontinuous + 200 A continuous (the 240.4(B) case)

Now the OCPD (300 A) is above the conductors' ampacity (255 A). That is legal only because of 240.4(B): 255 A does not correspond to a standard rating, the feeder is not a multioutlet receptacle branch circuit, and 300 A ≤ 800 A — so the next higher standard size is permitted. If the required rating had landed on a standard value (say 250 A exactly), 240.4(B) would not apply and the OCPD could not exceed the conductor ampacity without other 240.4 permission. The 100% exception is a trap here: it drops the OCPD to 205 → 225 A (one standard size smaller), but the conductors must still be protected at the OCPD rating — and the smallest 75 °C Cu conductor at ≥225 A is 4/0 AWG (230 A), a size larger than the 250 kcmil the standard path uses at 255 A. The exception's wire savings only appear when the 100% sum lands on a smaller Table 310.16 row — as in EX2.

EX5 — 60 A all-continuous, 60 °C terminations (the column that bites)

The OCPD side (75 A → 80 A) is identical in both columns — 215.3 does not care about temperature. The conductor side is where 110.14(C) bites: at 60 °C terminations (equipment ≤100 A, or marked 14 AWG–1 AWG), 4 AWG's 60 °C ampacity is only 70 A < 75 A, so you step up to 3 AWG. Quote the column with the size. Full treatment of the temperature-column trap in the 215.2 feeder ampacity article → and the 110.14(C) article →.

Gotchas

• "215.3 sizes the wire" — wrong. 215.3 sets the OCPD floor; 215.2 sets the conductor ampacity. Same 125% language, two different deliverables. Write both on the schedule.
• The exception is one exception (post-2020). Pre-2018 designs citing "215.3 Exception No. 2" for 600–1000 V feeders are citing a section that no longer exists. The 2020/2023 text has a single (unnumbered) Exception for the 100% listed assembly.
• The 100% exception covers the assembly, not the wire. "Where the assembly, including the overcurrent devices, is listed for operation at 100 percent of its rating." A listed panel alone is not the whole assembly.
• 240.4(B) is the only reason EX4 works. OCPD 300 A on 255 A conductors needs the next-standard-size allowance — and its three conditions (not a multioutlet receptacle branch circuit, ampacity not a standard rating, next size ≤ 800 A) all have to hold. Above 800 A the allowance stops working entirely (2023: 240.4(C) then requires conductor ampacity ≥ OCPD rating).
• 215.3's floor is a floor. You may always go to a larger standard size (up to the conductor-protection limits) — e.g. a 125 A OCPD on the EX1 feeder is permitted if 3 AWG (100 A) still cannot be protected at 125 A … wait: it can't (125 > 100, and 240.4(B) is unavailable because the next step from 100 A would be 125 A with the ampacity being a standard rating — 240.4(B) condition 2 fails). Larger OCPD = larger wire. The floor is the minimum, the conductors are the ceiling.
• Over-1000 V is a different article now. In 2023, Article 215 stops at 1000 V ac / 1500 V dc. Over-1000 V feeders: 235.201–235.203 (Part III of Article 235, with 235.203 the OCPD pointer and 235.202 the ampacity rule), and the over-1000 V OCPD device requirements live in the new Article 245. In 2020 the picture was transitional: 215.3's Exception No. 2 (which pointed 600–1000 V feeders at Parts I–VII and >1000 V feeders at Part IX) was deleted, but Article 240 Part IX itself was still in the 2020 code. 2017 designs cite Part IX of Article 240 via the deleted exception.
• The 215.2(A)(3) 55-A service guard is not here. If the feeder carries the total load of a ≤55 A service, the feeder conductors must match the service conductors' ampacity — that is 215.2(A)(3), covered in the 215.2 article →.

The method, step by step

1. Split the load into continuous (3+ hours expected — Article 100 definition) and noncontinuous.
2. 215.3 floor: OCPD rating ≥ noncontinuous + 125% × continuous. If the assembly (including the OCPDs) is listed for 100% operation, the floor is the plain sum.
3. Standard rating: round the floor up to the next value in Table 240.6(A) (15 … 6000 A).
4. Conductors (215.2): ampacity ≥ larger of (a) the same 125%-loaded number and (b) the maximum load served after 310.14/310.15 adjustments — in the applicable 110.14(C) column (60 °C / 75 °C / 90 °C derating base). Full method in the 215.2 article →.
5. 240.4 check: the OCPD must protect the conductors per their ampacity; 240.4(B) permits one standard size up when the ampacity is not a standard rating (≤ 800 A, not a multioutlet receptacle branch circuit).
6. Quote both: "OCPD 100 A (215.3), 3 AWG Cu @ 75 °C (215.2 / Table 310.16)" — and the edition.

FAQ

Q: Is the 215.3 OCPD rule different for 480 V feeders versus 120/240 V feeders?
A: No, not anymore. In the 2017 NEC, a 600–1000 V feeder went through deleted Exception No. 2 to Parts I–VII of Article 240 anyway — the same general OCPD requirements 120/240 V feeders use. Since 2020, all feeders up to 1000 V nominal take the plain 215.3 text with no exception; since 2023, all feeders up to 1000 V ac / 1500 V dc are in scope of Article 215 at all. Only above that line does the article split (235.201 onward).

Q: Can a feeder OCPD be smaller than the 215.3 floor?
A: No. "The rating of the overcurrent device shall not be less than the noncontinuous load plus 125 percent of the continuous load." The only path to a smaller floor is the 100% listed-assembly exception — and it changes the floor to the sum, not below it.

Q: What protects the feeder's neutral?
A: Nothing — 240.22 prohibits an OCPD in the grounded conductor unless it opens all conductors simultaneously (and 230.90(B) says the same for the service). Feeder neutral sizing is 215.2(A)(2) / 250.122, with the load per 220.61 — see the 220.61 article →.

Q: Where do I find the 2017 668.3(C) exemption in full?
A: Article 668 (Electrolytic Cells), 668.3 "Other Articles": (C)(1) exempts cell-line conductors from Articles 110, 210, 215, 220, and 225 (see 668.11); (C)(2) exempts cell process power from Article 240; (C)(4) exempts cell line working-zone equipment from Articles 110, 210, 215, 220, and 225 (see 668.30). All three quoted from the 2017 text on disk.

Q: Which edition does PanelWright implement?
A: The 2017–2023 rule set for feeders ≤1000 V — the 215.3 floor is identical 2020/2023, and the 125% multiplier + 240.6(A) standard list (15–6000 A, pre-2023) is what the cores use. The 2023 addition of 10 A to Table 240.6(A) is documented but not implemented in the cores yet. Verify against the edition adopted in your jurisdiction.

Free, in-browser, no account. The 220.82 service card rolls a real dwelling load up to the feeder current; the 215.2/240.6 rules above are the code-side explanation of the numbers it produces.