7.4 Continuous Loads & OCPD Sizing

Continuous Loads Tie Feeder Ampacity to Breaker Size

Sections 7.1–7.3 taught feeder ampacity, Article 240 device selection, and taps. This section welds them together with the continuous-load 125% rules that appear repeatedly on the Arkansas Journeyman (Prov) exam. If you remember only one sizing slogan for this chapter, make it: size for continuous load at 125%, then pick a standard OCPD that protects the conductors under 240.4.

Tab Article 100 (Continuous Load), 210.19, 210.20, 215.2, 215.3, 230.42 (for service comparisons), 240.4, and 240.6.

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Definition — Continuous Load

Continuous load (Art. 100): A load where the maximum current is expected to continue for 3 hours or more.

Exam recognition cues:

• Store or warehouse lighting left on for business hours.
• Office lighting and certain receptacle loads treated as continuous in design notes.
• Industrial process heaters or equipment specified as continuous.
• Stems that explicitly say “continuous load” or “operates for 3 hours or more.”

If the stem does not establish continuity, do not invent a 125% adder for the entire load. Conversely, when the stem says continuous, missing the 125% factor is an instant miss.

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Why 125% Exists

Continuous current heats conductors and OCPDs for extended periods. The Code’s 125% factor builds margin into:

• Conductor ampacity requirements for feeders and branch circuits.
• OCPD ratings that supply those circuits (unless equipment is listed for operation at 100% of its rating under the applicable section).

Think of 125% as applying to the continuous portion, then adding noncontinuous load at 100%, unless a specific rule says otherwise.

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Branch-Circuit Continuous-Load Rules — 210.19 / 210.20

For branch circuits (needed because feeder stems sometimes mix in branch math, and the same 125% logic appears in both places):

• 210.19(A) — branch-circuit conductors shall have ampacity not less than the maximum load to be served; for continuous loads, ampacity not less than noncontinuous + 125% continuous (parallel structure to feeders).
• 210.20(A) — branch-circuit OCPDs shall have a rating not less than the noncontinuous load plus 125% of the continuous load, with the listed 100%-rated assembly exception path.

These branch rules mirror feeder rules so you do not learn two contradictory formulas.

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Feeder Continuous-Load Rules — 215.2 / 215.3

Conductors — 215.2(A)(1)

Feeder conductor ampacity ≥ noncontinuous load + 125% continuous load (absent the listed-assembly exception).

Overcurrent devices — 215.3

215.3 requires the feeder overcurrent device rating / setting to be not less than the noncontinuous load plus 125% of the continuous load. Exception: where the assembly — including the OCPD — is listed for operation at 100% of its rating, the continuous load may be permitted up to the device’s rating under the exception’s conditions.

Prov paired question pattern:

1. Compute minimum feeder ampacity (215.2).
2. Compute minimum OCPD rating (215.3).
3. Choose conductors from Table 310.16 that meet ampacity.
4. Choose a standard OCPD from 240.6(A) that is ≥ the 215.3 minimum.
5. Verify 240.4 still protects those conductors (including 240.4(B)/(C)/(D) as applicable).

Often the conductor ampacity minimum and the OCPD minimum calculate to the same 125% number before standard-size rounding — then 240.4(B) may allow the next standard size above conductor ampacity when conditions are met.

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Worked Example (Open-Book Style)

Feeder load: 80 A continuous + 30 A noncontinuous.

1. Minimum ampacity / minimum OCPD basis = 30 + (80 × 1.25) = 30 + 100 = 130 A.
2. Conductors: select a copper size from Table 310.16 (correct temperature column) with ampacity ≥ 130 A after adjustment/correction.
3. OCPD: 130 A is not a standard 240.6(A) rating. Nearby standards include 125 A and 150 A. Because 125 A is below the 130 A continuous-load minimum, 125 A is too small. Select 150 A if that rating also satisfies conductor protection rules.
4. Confirm the chosen conductors’ ampacity can be protected by 150 A under 240.4 (next-size-up / ampacity relationship).

Trap: Calculating 80 + 30 = 110 A and picking a 110 A or 125 A breaker without the continuous 125% adder.

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100%-Rated Assemblies — Use Only When the Stem Gives Them

The exception path for equipment listed for 100% continuous operation is real, but Prov distractors love it. Apply it only when:

• The stem states the breaker/assembly is listed/rated for 100% operation, and
• You verify the exception language in 215.3 / 210.20 (and related equipment standards).

Otherwise, default to 125% of continuous + 100% noncontinuous.

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Interaction with Services (Do Not Cross-Wire Articles)

230.42 uses the same continuous-load philosophy for service-entrance conductors. That does not mean you cite 230.42 on a feeder stem. Identity check:

Same math family, different section numbers — answers are often wrong solely because of the wrong article citation in a “which section requires…” stem.

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Continuous Loads on Taps

If a feeder tap terminates in an OCPD that supplies continuous load, the terminating device still needs the 215.3 / 210.20 continuous-load rating logic for what it supplies. The upstream feeder OCPD protecting the large feeder is sized for the feeder’s load; the tap rule only allows unprotected (or differently protected) conductor length under 240.21 — it does not erase continuous-load sizing at the load-end device.

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Multioutlet and Receptacle Nuances

For branch circuits supplying cord-and-plug connected equipment, continuous-load and receptacle rules interact with Article 210 ratings. Also remember 240.4(B) denies next-size-up for certain multi-receptacle portable-load branch circuits. Continuous-load math and next-size-up permission are independent checks — both must pass.

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Practical Exam Checklist — Continuous Load Stems

1. Does the stem establish a continuous load (definition or explicit label)?
2. Split continuous vs noncontinuous amperes.
3. Compute I_req = noncontinuous + 1.25 × continuous.
4. Apply I_req to conductors (215.2 / 210.19) and to OCPDs (215.3 / 210.20).
5. Select standard OCPD ≥ I_req from 240.6(A).
6. Confirm 240.4 conductor protection (small-conductor caps, ≤800 A next size, >800 A no round-up).
7. Only if listed 100%-rated assembly is in the stem, reopen the exception.

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Timed Tips for the Whole Chapter 7 Cluster

• Feeder identity first (Art. 100 / 215 vs 230 vs 210).
• Continuous 125% next (215.2 / 215.3).
• Table 310.16 + 110.14(C) for conductors.
• 240.6 + 240.4 for device pairing.
• 240.21 only when length-from-supply / tap language appears.

Mastering that order turns the 8-item Services/Feeders/OCP block into a lookup sequence instead of a memory contest on a 3-hour, 60-question, 70% Prov Arkansas JW exam using NEC 2023.