NEC 430.32 + 430.36 — Motor Overload Protection (Nameplate vs Table FLC)

How to set the motor overload device — 430.32 (the separate overload device at 125%/115% of the NAMEPLATE, the thermal protector at 170/156/140% of the TABLE FLC, the 430.32(C) 140/130% higher-setting cap, the 430.32(D) branch-OCPD path, and 430.35(A)'s 400% shunt ceiling), plus 430.33 (intermittent duty), 430.36/430.37/430.38 (which conductors and how many units), 430.31 (the scope). The nameplate-current pair to the previous article (430.22/430.52 single-motor branch circuit). Verbatim 2017 and 2023, the verified edition deltas, and six worked examples — every number computed by the shipped calculator core. Last updated 2026-09-04 (written for PanelWright v1.16).

What these sections are (and the one distinction that drives them)

Article 430, Part III is "Overload Protection," and 430.31 says what the whole part is for: it specifies the overload devices intended to protect motors, motor-control apparatus, and motor branch-circuit conductors against excessive heating due to motor overloads and failure to start. The sections below answer the practical questions in order:

• 430.32 — "How do I SET the overload?" The main rule. For a continuous-duty motor over 1 hp, a separate overload device responsive to motor current is set/rated at no more than 125% of the NAMEPLATE full-load current (or 115% for standard motors). A thermal protector is capped at 170/156/140% of the TABLE FLC. And 430.32(C) lets you go higher to start the motor, capped at 140/130%.
• 430.33 — "Is this even continuous duty?" A short-time/intermittent/periodic/varying-duty motor may use the branch OCPD (430.52) as its overload protection instead of a separate device.
• 430.35 — "Can I cut it out while starting?" Shunting/cutout during starting is allowed for a manually-started motor only under the 400% OCPD condition; it is barred for an automatically-started motor except with listed means.
• 430.36 / 430.37 — "Which conductors get the overload?" Fuses go in each ungrounded conductor (plus the grounded one on a 3-wire 3-phase ac system); non-fuse devices follow Table 430.37 (number and location of overload units).
• 430.38 — "How many conductors must it open?" A non-fuse, non-thermal overload device must simultaneously open enough ungrounded conductors to interrupt current to the motor.

The one distinction that drives all of Part III: the separate overload device (430.32(A)(1)) is sized on the nameplate full-load current, while the thermal protector (430.32(A)(2)) and the branch OCPD (430.52) are sized on the table full-load current (430.248/430.250). Mixing those two bases is the single most common motor-overload error — and it is why this article (the "nameplate-current" article) is the natural companion to the previous one (the "table-FLC-current" article, 430.22/430.52).

430.31 — General (the scope of Part III)

2017 (verbatim on disk)

Three scope facts to keep: (1) Part III covers the overload device — a different device from the branch-circuit short-circuit/ground-fault OCPD of Part IV (430.52). (2) Where a power loss would be hazardous (fire pumps), the code does not require overload protection at all — the 695.7 fire-pump supply-conductor rule governs instead. (3) Part III stops at 1000 volts nominal; higher-voltage motor circuits are in Part XI. 430.31's own Informational Note No. 1 points to Annex D, Example D8 — a worked motor-overload example.

430.32 — Continuous-Duty Motors: the overload rule (A)–(E)

2017 (verbatim on disk)

Break the section down, in the order you would apply it in the field:

1. (A)(1) Separate Overload Device — the default, the NAMEPLATE path. The device is "selected to trip or rated at no more than" 125% of the nameplate FLC (SF ≥ 1.15 or temp-rise ≤ 40 °C) or 115% (all other motors). The basis is the nameplate, not the table. EX1 and EX2 apply it. The wye-delta note is the reminder that when the device does not see the full nameplate current, the percentage is adjusted (and the manufacturer's table governs).
2. (A)(2) Thermal Protector — the TABLE path. A thermal protector (the bimetal/wax element inside a small motor's winding) has its ultimate trip current capped at 170/156/140% of the table FLC (430.248/249/250), bucketed at 9 A and 20 A. EX3 applies it. This is the flip side of the (A)(1) rule: same section, different device, different current basis.
3. (A)(3) Integral with Motor and (A)(4) Larger Than 1500 hp are the two remaining >1 hp means — an approved-assembly integral device, and (for >1500 hp) embedded temperature detectors. Rare in the field but present on exams.
4. (B) One Horsepower or Less, Automatically Started — four means: (B)(1) a separate device per (A)(1) [EX4], (B)(2) a thermal protector, (B)(3) an integral device (including the oil-burner safety-controls case), (B)(4) impedance protection. The 1/20 hp Informational Note (clock motors, series/torque motors) is the small-motor scope.
5. (C) Selection of Overload Device — the higher-setting cap. If (A)(1)/(B)(1) is too small to start, you may go higher, but only to 140% (SF ≥ 1.15 / temp-rise ≤ 40 °C) or 130% (all other) of the nameplate. The device needs time delay (or a 430.35 shunt) to ride through the start. The Class 10/20/30 Informational Note is the practical "more class = more starting margin" rule.
6. (D) One Horsepower or Less, Nonautomatically Started — the "do I need a separate device?" section. (D)(2)(a): controller within sight → the branch OCPD (430.52) IS the overload protection [EX5]; the 120-V/20-A exception is for the not-permanently-installed case. (D)(1)/(D)(2)(b): permanently installed, or controller not within sight → full 430.32(B) protection.
7. (E) Wound-Rotor Secondaries — the secondary circuits may ride on the motor-overload device.

The (A)(1) vs (A)(2) split, side by side (this is the whole article in one table):

430.33 + 430.35 — duty, and shunting during starting

430.33 Intermittent and Similar Duty (2017, verbatim on disk)

430.33 is the "get out of jail free" for non-continuous duty: if the motor is genuinely short-time/intermittent/periodic/varying (the Table 430.22(E) classifications), the branch OCPD may serve as the overload protection — no separate element. The default is the strong one, though: any motor is continuous duty unless you can show it cannot run continuously under any condition of use. EX6's second half touches this.

430.35 Shunting During Starting Period (2017, verbatim on disk)

The 400% number in 430.35(A) is the ceiling for the OCPD (not the overload element) that must be operative during starting if you want to shunt the overload out: fuses or an inverse-time breaker at not over 400% of the FLC, and the shunting device must not be leaveable in the start position. For an automatically-started motor the answer is generally "no" — the overload must stay in — except under the listed-means Exception (sense rotation, limit shunt time, shutdown/manual restart). EX6 computes the 400% ceiling and checks the OCPD against it.

430.36 / 430.37 / 430.38 — which conductors, how many units, how many to open

430.36 Fuses — In Which Conductor (2017, verbatim on disk)

One overload fuse per ungrounded conductor, always. The only place the grounded conductor gets a fuse is the 3-wire, 3-phase ac system with one grounded conductor. This is a "where does the device live" rule, not a sizing rule.

430.37 Devices Other Than Fuses — In Which Conductor + Table 430.37 (2017, verbatim on disk)

Table 430.37 is a "how many and where" table for non-fuse overload devices (the trip coil / relay / electronic element). The common rows: a 2-wire 1-phase circuit needs 1 unit (in either conductor if ungrounded, the ungrounded one if grounded); a 3-phase circuit needs 3 (one in each phase) — with the exception that a unit per phase is not required where other approved protection exists (e.g. a thermal protector that interrupts all phases by construction). 2-phase rows (mostly legacy) need 2.

430.38 Number of Conductors Opened by Overload Device (2017, verbatim on disk)

430.38 is the "does it actually stop the motor" rule: a non-fuse, non-thermal overload device must open enough ungrounded conductors at the same time to de-energize the motor. (A thermal protector or a fuse inherently opens in a single conductor path or per the 430.36/37 layout; a relay that only opened one phase of a 3-phase motor would leave it running on two phases — locked-rotor heating — and would violate 430.38.)

The edition history, verified line by line

Bottom line: the numbers never moved. 125/115% (nameplate), 170/156/140% (table), 140/130% (the (C) cap), and the 400% shunt ceiling are identical in 2017 and 2023. What moved: 2023 adds the electronic-protection sentence to the two thermal-protector subsections — (A)(2) gains it, plus "approved..."→"shall be approved..." and "thermally protected"→"thermally or electronically protected"; (B)(2) gains the same sentence — reflecting that "overload protection" now commonly means an electronic element, not just a bimetal one. Also: (A)(1) 460.9 note reworded, 430.33 re-cites 430.52→430.52(C)(1), 430.31 restructures into (A)/(B), 430.35 renumbers its exception. A 2017 design note citing "430.32(A)(2)" with 170/156/140% is still correct in substance in the 2023 code. 2014 not on disk (no 2014 claim).

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

Every number below is produced by the shipped cores in app.js (nextStdBreaker(), pickConductor31016(), smallConductorCap() — node-invoked this session via compute_art39.js) and is asserted in the public test suite (test/run_tests.js in the public repo). The overload PERCENTAGES (125/115, 170/156/140, 140/130, 400) and the two FLA tables (430.248 single-phase, 430.250 three-phase) are code — the percentages transcribed verbatim from the on-disk 2017 scan (verified by verify_art39.py, 73/73), the FLA cells from the same clean live tables Article 38 live-verified (extended with the ≤1 hp rows). Table 310.16 values are base values (30 °C ambient, ≤3 current-carrying conductors). The branch-conductor picks in EX1/EX6 run the shipped pickConductor31016() at 430.22's 125% (the previous article's rule) so the two articles show the full motor-circuit picture together.

EX1 — 3 hp, 230 V, 3-phase, SF 1.15, continuous: the everyday nameplate setting (430.32(A)(1))

A 3 hp, 230 V three-phase continuous-duty motor with a marked service factor of 1.15. Nameplate FLC: 9.5 A; table FLC (Table 430.250): 9.6 A. The overload setting uses the nameplate.

The separate overload element is set at 125% of the nameplate (9.5 A → 11.88 A). Note the table FLC (9.6 A) is shown for contrast only — it is not the setting basis for a separate device; it is the basis for the (A)(2) thermal path and for the 430.22 conductors / 430.52 OCPD. If 11.88 A nuisance-trips on the start, 430.32(C) permits going up to 140% of nameplate = 13.30 A — no further.

EX2 — 5 hp, 230 V, 3-phase, standard motor (no SF ≥ 1.15): the 115% / 130% pair

A 5 hp, 230 V three-phase continuous motor with no marked service factor ≥ 1.15 and a temperature rise over 40 °C (a "standard" motor). Nameplate FLC: 15.6 A; table FLC: 15.2 A.

The distinction that trips people up: a standard motor (no SF ≥ 1.15, temp-rise > 40 °C) gets 115% of nameplate as the setting and 130% as the (C) cap — not 125/140. The SF/temperature-rise class determines which column you are in, for both the base and the cap.

EX3 — 430.32(A)(2) thermal protector: the table-FLC buckets (170 / 156 / 140)

Two motors that rely on an integral thermal protector. The trip current is a percentage of the table FLC, bucketed at 9 A and 20 A.

Same section as EX1/EX2, different device, different basis: the thermal protector rides on the table FLC, not the nameplate. 5.8 A is in the ≤9 A bucket (170%); 15.2 A is in the 9.1–20 A bucket (156%). A motor with table FLC above 20 A would be in the 140% bucket. This is the mirror image of the (A)(1) nameplate rule — the two bases coexist in one section, which is why the article exists.

EX4 — 1/2 hp, 230 V, 1-phase, ≤1 hp automatically started (430.32(B)(1))

A 1/2 hp, 230 V single-phase motor that starts automatically (e.g. a small pump or fan with a float or thermostat). Nameplate FLC: 4.4 A, SF 1.15. Using mean (B)(1), it follows the (A)(1) nameplate rule.

A ≤1 hp automatically-started motor must have one of four means (430.32(B)): (B)(1) a separate device per (A)(1) — shown here, (B)(2) a thermal protector, (B)(3) safety controls (the oil-burner case), or (B)(4) impedance protection. (B)(1) simply re-uses the (A)(1) nameplate percentages, so 4.4 A → 5.50 A (cap 6.16 A).

EX5 — 1/4 hp, 230 V, 1-phase, manually started, controller within sight (430.32(D)(2)(a))

A 1/4 hp, 230 V single-phase motor that is manually started (a switch at the machine) with the controller in sight. Table FLC (430.248): 2.8 A. No separate overload device is required — the branch OCPD is the overload protection.

This is the "no separate overload" path: 430.32(D)(2)(a) lets the 430.52 branch OCPD serve as the overload protection for a ≤1 hp manually-started motor with the controller in sight. The 15 A inverse-time breaker (250% of the 2.8 A table FLC, rounded up to the next standard size) is both the short-circuit/ground-fault device and the overload protection. The 120-V/20-A exception covers a not-permanently-installed motor on a 120-volt circuit. (If the controller were not in sight, or the motor permanently installed, 430.32(B) would apply instead.)

EX6 — 10 hp, 230 V, 3-phase wye-start: the 430.35(A) 400% shunt ceiling + 430.33 duty

A 10 hp, 230 V three-phase wye-start motor with a long starting period. Table FLC: 28.0 A; nameplate FLC: 28.5 A. The controller shunts the overload out during starting; 430.35(A) sets the condition for that to be allowed.

The overload (35.63 A, 125% of nameplate) is shunted out during the start — legal because the inverse-time branch OCPD (70 A) is at or below the 430.35(A) 400% ceiling (112 A) and is operative during the starting period. Once the motor reaches speed, the overload is restored and protects the 8 AWG Cu conductors at running current. If this motor were on short-time/intermittent/periodic/varying duty (Table 430.22(E)), 430.33 would instead let the OCPD be the overload protection outright — no shunt dance needed.

Gotchas

• Nameplate for the separate device, table for the thermal protector. 430.32(A)(1) sizes on the NAMEPLATE FLC (125/115%); 430.32(A)(2) sizes on the TABLE FLC (170/156/140%). They are in the same section but use different current bases — the #1 motor-overload error is applying the table FLC to a separate device (or the nameplate to a thermal cap). EX1/EX2 vs EX3 make the split concrete.
• The 125/115% and 140/130% are class-dependent, not fixed. The SF ≥ 1.15 / temp-rise ≤ 40 °C class gets 125% (base) and 140% (the (C) cap); the "all other motors" class gets 115% and 130%. Check the nameplate markings before picking a column.
• 430.32(C) is a cap, not a free pass. You may raise the setting to start the motor, but only to 140% (or 130%) of nameplate — never higher. And the device still needs time delay (or a 430.35 shunt) to ride the start.
• The 400% in 430.35(A) is an OCPD ceiling, not an overload setting. It is the maximum rating of the fuses/inverse-time breaker that must be operative during starting to allow shunting the overload out. Do not set the overload element at 400% — it stays at the (A)(1)/(C) value and is simply cut out during the start.
• Automatically started = no shunt (except listed means). 430.35(B) bars shunting/cutout for an automatically-started motor unless the starting period exceeds available overload time delay AND listed means sense rotation, limit shunt time, and provide shutdown/manual restart. A float-switched pump (auto-start) cannot just have its overload bypassed on start.
• ≤1 hp manually-started, controller in sight = no separate device needed. 430.32(D)(2)(a): the 430.52 branch OCPD is the overload protection (with the 120-V/20-A exception). ≤1 hp automatically-started, or permanently installed, or controller not in sight → 430.32(B) applies (a separate device or one of the other three means).
• Continuous duty is the default. 430.33's "any motor application shall be considered continuous duty unless..." means you must positively show non-continuous operation before using the OCPD as the overload protection. When in doubt, install the separate overload device.
• One unit per ungrounded conductor (Table 430.37), and open enough to stop the motor (430.38). 3-phase → 3 overload units (one per phase), with the exception for other approved means; the device must simultaneously open enough ungrounded conductors to de-energize the motor. A relay that opened only one phase of a 3-phase motor leaves it running (locked-rotor heating) and violates 430.38.
• The 2023 "electronically protected" addition. 2023 adds, to both thermal-protector subsections, that an electronically protected motor must be approved to prevent dangerous overheating due to failure of the electronic control. The numeric percentages are unchanged — but if you are specifying an electronic overload element in the 2023 code, the approval basis is now stated in the code, not just in the listing.
• The 2020 body of Article 430 is not on disk. The on-disk 2020 full-code scan ends at Article 230 (its only Article 430 references are cross-references inside Articles 110–230), so the 430.32/430.36 2017→2020 word-diff is not available. The numeric rules are stable 2017–2023; the verified deltas are 2017→2023 (the electronic-protection sentence, the 460.9 reword, the 430.52(C)(1) re-cite, the 430.35 renumber). If your jurisdiction adopted 2020, the rule set is the same.

The method, step by step

1. Decide the duty. Continuous duty (the default) → 430.32. Short-time/intermittent/periodic/varying (Table 430.22(E)) → 430.33 may let the OCPD be the overload protection. ≤1 hp → check the (B) auto-started vs (D) manual-started path first.
2. Pick the device and the current basis. Separate overload device → NAMEPLATE FLC (430.32(A)(1)). Thermal protector → TABLE FLC (430.32(A)(2), 430.248/249/250). ≤1 hp manually-started controller-in-sight → the 430.52 OCPD (430.32(D)(2)(a)).
3. Apply the percentage. (A)(1): 125% (SF ≥ 1.15 / 40 °C) or 115% (all other) of nameplate. (A)(2): 170/156/140% of table FLC (buckets ≤9 A / 9.1–20 A / >20 A).
4. If it trips on start, use 430.32(C). Raise the setting, but only to 140% (or 130%) of nameplate. Add time delay (Class 20/30), or shunt per 430.35 if the OCPD is ≤400% FLC and operative during start.
5. Place the device (430.36/430.37). Fuses: one per ungrounded conductor (+ the grounded one on 3-wire 3-phase ac). Non-fuse: Table 430.37 number/location. Ensure it opens enough ungrounded conductors to stop the motor (430.38).
6. Quote both, with the edition. "Overload 12 A (430.32(A)(1), 125% of 9.5 A nameplate, SF 1.15); branch OCPD 15 A inverse (430.52, 250% of 9.6 A table FLC); conductors 14 AWG Cu (430.22, 125% table FLC, 60 °C column). 2017/2023 numbers identical; 2023 adds the electronic-protection sentence to (A)(2)." — and note the nameplate-vs-table basis explicitly, because it is the whole point.

FAQ

Q: What percentage do I set my motor overload relay at?
A: 430.32(A)(1) — 125% of the NAMEPLATE full-load current if the motor has a marked service factor of 1.15 or greater or a marked temperature rise of 40 °C or less, else 115%. 3 hp, 230 V, 3-ph, SF 1.15 (nameplate 9.5 A) → 11.88 A. The basis is the nameplate, not the table FLC — that is the key difference from the conductor/OCPD rules.

Q: The motor only has a thermal protector. What's the cap?
A: 430.32(A)(2) — a percentage of the TABLE FLC: 170% (≤9 A), 156% (9.1–20 A), 140% (>20 A). 1 hp 3-ph 230 V (5.8 A) → 9.86 A; 5 hp 3-ph 230 V (15.2 A) → 23.71 A.

Q: It trips on starting. Can I raise it?
A: Yes, up to 430.32(C)'s cap — 140% of nameplate (SF ≥ 1.15 / 40 °C) or 130% (all other). Add time delay (Class 20/30) or shunt per 430.35 (OCPD ≤400% FLC, operative during start). Never above the (C) cap.

Q: Do I need a separate overload on a small motor?
A: Not if it's ≤1 hp, manually started, and the controller is in sight — 430.32(D)(2)(a) lets the 430.52 branch OCPD be the overload protection (120-V/20-A exception for not-permanently-installed). ≤1 hp automatically started → 430.32(B) (one of four means). 430.33: a short-time/intermittent/periodic/varying-duty motor may use the OCPD outright.

Q: When can I cut the overload out during starting?
A: 430.35(A) — only for a manually-started motor, and only if the shunt device can't be left in the start position AND fuses/inverse OCPD at ≤400% of FLC are operative during the start. 430.35(B) — not for an automatically-started motor, except with listed means (sense rotation, limit shunt time, shutdown/manual restart).

Q: Which conductors get the overload, and what changed in 2023?
A: 430.36 (fuses: one per ungrounded conductor, + grounded on 3-wire 3-phase ac); 430.37 Table 430.37 (non-fuse: 1 unit 1-phase, 3 one-per-phase 3-phase, with the other-approved-means exception); 430.38 (open enough ungrounded conductors to stop the motor). 2017→2023: the "electronically protected motor" sentence added to (A)(2)/(B)(2), the 460.9 note reworded, 430.52→430.52(C)(1) re-cite, 430.35 renumber. Numbers unchanged; 430.36/37/38 bodies word-identical.

Free, in-browser, no account. The panel schedule's conductor and OCPD picks run the same shipped cores that computed the six examples above.