4.4 Neutral Loads & Optional Calculation Methods

Neutral Conductor Sizing (220.61)

The feeder or service neutral is sized for the maximum unbalanced load — the largest net load between the neutral and any one ungrounded conductor [220.61(A)]. For a typical 120/240V single-phase service, that's the larger of the two ungrounded conductor loads minus what's balanced across the phases.

Permitted 70% Reductions (220.61(B))

(B)(1): The neutral for household electric ranges, wall-mounted ovens, counter-mounted cooking units, and electric dryers may be sized at 70% of the demand load determined by Tables 220.55 and 220.54. Example: a 12 kW range → 8 kW demand → neutral = 8 × 70% = 5.6 kW.

(B)(2): For 3-wire DC, single-phase AC, 4-wire 3-phase, and 3-wire or 5-wire 2-phase systems, the portion of unbalanced load exceeding 200 amperes may be reduced by 70%. Example: 600A neutral → first 200 A at 100% + (600-200) × 70% = 200 + 280 = 480 A.

Prohibited Reductions (220.61(C))

No neutral reduction is permitted for:

• Any portion of a 3-wire circuit (2 ungrounded + neutral) supplied by a 4-wire 3-phase wye system.
• Any portion consisting of nonlinear loads on a 4-wire wye-connected 3-phase system (harmonic currents can overload the neutral).

This is a heavily tested distinction: 220.61(B) gives the reduction, 220.61(C) takes it away for wye/nonlinear scenarios.

Optional Method — Single Dwelling (220.82)

220.82(A) allows the optional method for a dwelling served by a single 120/240V or 120/208V, 3-wire set of service/feeder conductors rated 100A or larger.

Step 1 — Total connected load less HVAC [220.82(B)]:

• General lighting at 3 VA/sq ft
• Two small-appliance circuits (1500 VA each)
• One laundry circuit (1500 VA)
• Fixed appliances/motors at nameplate

Step 2 — Apply demand factor:

• First 10 kVA at 100%
• Remainder at 40%

Step 3 — Add HVAC per 220.82(C), choosing the largest of:

• A/C at 100% nameplate
• Heat pump (no supplemental) at 100%
• Heat pump with supplemental: 100% compressor + 65% supplemental
• Electric space heating (≤3 units): 65%
• Electric space heating (≥4 units): 40%

Worked example: 2000 sq ft dwelling, range 8 kW, dryer 5 kW, dishwasher 1.2 kW, disposal 0.9 kW, water heater 4 kW, A/C 5 kW.

Step 1: 6000 (lighting) + 3000 (SA) + 1500 (laundry) + 8000 (range) + 5000 (dryer) + 1200 + 900 + 4000 = 29,600 VA

Step 2: First 10,000 × 100% = 10,000; remaining 19,600 × 40% = 7840. Demand = 17,840 VA

Step 3: A/C at 100% = 5000 VA

Total = 22,840 VA ÷ 240 = 95.2 A → 100A service.

Compare to the standard method in section 4.2, which yielded ~103 A — the optional method saved enough to land cleanly on 100 A.

Optional Method — Existing Dwelling (220.83)

220.83 applies when adding loads to an existing dwelling whose service/feeder already has enough capacity. Two tracks:

• (A) No added A/C or electric space heating: First 8 kVA at 100%, remainder at 40% (Table 220.83(A)).
• (B) With added A/C or electric space heating: Same 8 kVA/40% split for other loads, plus heating or cooling at 100% of nameplate — choose the larger of heat or cooling, not both.

220.83 is the clipboard method electrification retrofits use to justify a heat pump or EV charger on an existing 200A service.

Optional Method — Multifamily (220.84)

220.84 may be used when each dwelling unit has electric cooking and electric heating and/or A/C, and is supplied by no more than one feeder.

Procedure:

1. Sum the connected load across all units (general lighting, small-appliance, laundry, all appliance nameplate, motors, and the larger of A/C or space heating per unit).
2. Apply Table 220.84 demand factor by number of units (e.g., 12 units ≈ 41%, declining with more units).
3. Add house loads (corridors, parking, common laundry) calculated per Article 220 Part III.
4. Size the building service conductors per Table 310.16 — NOT 310.12 (310.12 is for individual dwelling-unit feeders only).

Other Optional Methods

• Schools (220.84, with separate table) — actually a different procedure; some references cite Annex D example D5.
• Restaurants — optional method per Annex D.
• Recreational — optional method per Annex D.

These are lower-frequency exam material but the pattern is identical: sum connected, apply a table demand factor, add HVAC.

Comparison Table — Standard vs Optional

The optional method usually yields a smaller service, which is its appeal — but you must check eligibility.

Common Exam Traps

• Applying 220.61(B)(1) 70% reduction to a 4-wire 3-phase wye system (prohibited by 220.61(C)).
• Using the 10 kVA/40% optional split on a dwelling served by a 60A service (must be 100A+).
• Forgetting to take the larger of heating or cooling in 220.82(C) — adding both double-counts.
• Using Table 310.12 for a multifamily building service instead of 310.16.
• Confusing 220.82 (new single dwelling) with 220.83 (existing dwelling, 8 kVA breakpoint instead of 10 kVA).