3.1 Standard Dwelling Unit Load Calculations

Why Standard Method Matters on the Arkansas JW Exam

The Arkansas Journeyman Electrician exam (Prov / ADLL, NEC 2023, 60 questions, 3 hours, 70% pass) weights General Knowledge of the Electrical Trade and Calculations at 9 items. Load calculations dominate that block. Under timed open-book conditions you will not invent demand percentages — you will open Article 220, read the section that matches the occupancy, and apply the published NEC tables. This section covers the standard method for a single dwelling unit (Part III of Article 220). Optional dwelling and multifamily methods are in the next section.

Prov questions typically give square footage, a short appliance list, and ask for calculated VA, amperes at 240 V, or which demand factor applies. Your job is a repeatable workflow, not memorized answers.

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Exam Workflow — Standard Dwelling Feeder/Service

Use this order every time:

1. Floor area — outside dimensions; exclude open porches, garages, and unfinished spaces not adaptable for future use (see area rules tied to the general lighting calculation in Part III / 220.5 application notes).
2. General lighting — 220.41: not less than 3 VA/ft² × floor area.
3. Small-appliance + laundry — 220.52(A) and (B): add 1500 VA × 2 (minimum two small-appliance branch circuits) and 1500 VA laundry before demand factors.
4. Apply Table 220.45 demand factors to that combined lighting/SA/laundry subtotal (dwelling row).
5. Fixed appliances — nameplate loads; if four or more qualifying fastened-in-place appliances, 220.53 allows 75% of the sum (exclusions apply).
6. Clothes dryer(s) — 220.54: 5000 VA or nameplate, whichever is larger; Table 220.54 if multiple dryers.
7. Cooking equipment — 220.55 and Table 220.55 (and Notes).
8. Heating / A/C — 220.60 noncoincident loads: use the larger of noncoincident loads (typically heating vs cooling), not both at full nameplate unless they can operate together.
9. Largest motor — add 25% of the largest motor load (220.50 / motor rules as applied in Part III).
10. Sum → convert to amperes if asked: I = VA ÷ V (often 240 V for service/feeder questions).

Do not skip steps 3–4. Candidates who apply Table 220.45 only to lighting and forget to fold in the 4500 VA of small-appliance/laundry before demand factors lose easy points.

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Floor Area and General Lighting (220.41)

For dwelling units, NEC 2023 220.41 requires a unit load of not less than 3 volt-amperes per square foot. Compute floor area from the outside dimensions of the building, dwelling unit, or other area involved. Exclude open porches, garages, and unused or unfinished spaces not adaptable for future use.

Example: Outside dimensions 40 ft × 50 ft → 2000 ft². General lighting load = 2000 × 3 = 6000 VA.

That 6000 VA is not yet the feeder lighting demand. You still add small-appliance and laundry VA, then apply Table 220.45.

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Small-Appliance and Laundry Loads (220.52)

Per 220.52(A), each required 20-ampere small-appliance branch circuit is calculated at 1500 VA, and dwelling units require at least two. Per 220.52(B), the laundry branch circuit is calculated at 1500 VA (where required).

These 220.52 loads are included with the general lighting load and the demand factors of Table 220.45 are applied to the combined total. Installing extra small-appliance circuits does not automatically increase the calculated load beyond the Code minimums used in the calculation — follow what 220.52 and the problem statement require.

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Table 220.45 — Dwelling Lighting Demand Factors

Open Table 220.45 (Lighting Load Demand Factors). For dwelling units, the published breakpoints are:

Numbering trap for 2026 candidates: the 2023 NEC reorganized Article 220. The dwelling lighting demand factors that older notes and 2020-edition study guides call Table 220.42 are printed as Table 220.45 in the NEC 2023 book you carry into a Prov session. In the 2023 edition, 220.42 / Table 220.42(A) is the non-dwelling lighting unit load rule instead (§3.3). Arkansas tests on NEC 2023 — tab 220.45 for demand factors and do not waste clock hunting a dwelling row inside Table 220.42(A).

Worked demand on a 2000 ft² dwelling:

• Lighting = 6000 VA
• Small-appliance + laundry = 4500 VA
• Combined = 10,500 VA

Apply Table 220.45:

• First 3000 VA × 100% = 3000 VA
• Remaining 7500 VA × 35% = 2625 VA
• Lighting/SA/laundry demand = 5625 VA

On the exam, if options show 10,500 VA, that answer usually forgot the demand factor. If options show demand applied only to 6000 VA, that answer forgot 220.52.

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Fixed Appliances (220.53)

220.53 permits a demand factor of 75% for four or more fastened-in-place appliances (other than electric ranges, clothes dryers, space-heating equipment, or air-conditioning equipment) in a one-family, two-family, or multifamily dwelling. Typical qualifying nameplates: dishwasher, food-waste disposer, water heater, trash compactor, freezer — if fastened-in-place and rated within the section’s scope.

Example: Dishwasher 1200 VA + disposer 800 VA + water heater 4500 VA + compactor 900 VA = 7400 VA connected. Four appliances → 7400 × 0.75 = 5550 VA demand.

If only three appliances are listed, use 100% of the sum — the 75% factor needs four or more.

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Clothes Dryers (220.54) and Ranges (220.55)

Electric clothes dryers — 220.54: The load is 5000 VA or the nameplate rating, whichever is larger. For five or more dryers, apply the demand factors in Table 220.54 (look up the table; do not invent percentages).

Household cooking — 220.55 / Table 220.55: For one range rated 8¾ kW through 12 kW, Column C demand is commonly 8 kW (verify the exact row/column in your NEC). Note 1 to Table 220.55: for ranges over 12 kW through 27 kW, increase the Column C demand by 5% for each kW (or major fraction) above 12 kW.

Example — 14 kW range: Excess above 12 kW = 2 kW → 2 × 5% = 10% increase. Demand = 8 kW × 1.10 = 8.8 kW = 8800 VA.

Always open Table 220.55 for number of appliances and which column the question points to (A, B, or C).

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Noncoincident Loads and Largest Motor

220.60 Noncoincident Loads: Where it is unlikely that two or more noncoincident loads will be in use simultaneously, use the largest of those loads in the calculation. Classic exam pair: electric space heating vs air conditioning — include the larger, not both full nameplates, when they are noncoincident.

Largest motor adder: After assembling other loads, add 25% of the full-load current (or equivalent VA) of the largest motor as required by the Part III motor/appliance rules (220.50 application). If the problem gives a 1 hp garbage disposer already counted under 220.53, check whether the question also expects a separate 25% motor adder on the largest motor — read the stem carefully and follow Article 220’s cross-references to Article 430 where stated.

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Full Worked Example — 1800 ft² Single-Family Dwelling

Given: 1800 ft²; 12 kW range; 5.5 kW dryer; dishwasher 1400 VA; disposer 900 VA; water heater 4000 VA; fastened freezer 1200 VA; A/C 6000 VA; heat 8000 VA; 120/240 V service. Find approximate standard-method demand VA (ignore service minimum sizing for this illustration).

1. Lighting = 1800 × 3 = 5400 VA
2. SA + laundry = 4500 VA → combined = 9900 VA
3. Table 220.45: 3000 + (6900 × 0.35) = 3000 + 2415 = 5415 VA
4. Four fixed appliances: 1400 + 900 + 4000 + 1200 = 7500 → × 0.75 = 5625 VA (220.53)
5. Dryer: max(5000, 5500) = 5500 VA (220.54)
6. Range 12 kW → Table 220.55 Column C = 8000 VA (verify in table)
7. HVAC noncoincident (220.60): larger of 6000 and 8000 = 8000 VA
8. Subtotal (before any separate motor-adder nuance): 5415 + 5625 + 5500 + 8000 + 8000 = 32,540 VA
9. Amperes at 240 V: 32,540 ÷ 240 ≈ 136 A (then compare to next standard service size / conductor rules — often a follow-up question)

On Prov, you may be asked only for the lighting demand, only for the range demand, or for the HVAC selection under 220.60. Isolate the asked piece; do not over-calculate.

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Timed Open-Book Tips

• Tab Article 220 Part III, Table 220.45, Table 220.54, and Table 220.55 before the exam clock starts.
• Write the 10-step list on scratch paper once, then reuse it.
• Convert kW ↔ VA carefully (1 kW = 1000 VA for these Code calculations unless the problem states otherwise).
• Never apply dwelling optional-method percentages (220.82) when the question specifies the standard method — or vice versa.