How do you apply the NEC 220.44 receptacle demand factor?

A panel schedule lists the connected load on every circuit, but not every outlet is in use at once. NEC 220.44 lets the designer count receptacle loads in nondwelling units at less than their connected total. Confirm the section number and the rule against the edition of the code adopted where you build.

What is the demand calculation?

• Add up the connected receptacle load in kVA.
• Count the first 10 kVA at 100%.
• Count the part above 10 kVA at 50%.

Demand = 10 + 0.5 × (connected − 10), when connected load is above 10 kVA. The demand ratio is demand ÷ connected load, and multiplying each receptacle circuit by that ratio spreads the reduction across the phases.

What does a worked example look like?

A panel serves 28 kVA of connected receptacle load.

• Demand = 10 + 0.5 × (28 − 10) = 19 kVA.
• Demand ratio = 19 ÷ 28 = 0.679.
• Current for a 208 V three-phase supply = 19 × 1000 ÷ (√3 × 208) = 52.7 A.

The ratio goes on the receptacle circuits only. A circuit that is not a receptacle circuit keeps its own connected load.

How do circuits split across the phases?

A single-pole circuit puts its whole demand on its phase. A two-pole circuit puts half on each of its two phases, and a three-pole circuit a third on each. Phase imbalance is the largest deviation of any phase from the average, divided by the average, which shows whether loads should be moved between breakers.

What does this rule not cover?

It applies to receptacle loads, not to motors, continuous loads or other demand factors, and it does not check conductor ampacity, breaker coordination, voltage drop, harmonics or short-circuit ratings. Dwelling units follow different rules. Treat the result as a design aid and have the design reviewed against the applicable code and by a licensed professional.

The electrical panel load schedule applies this rule to a 42-circuit 208Y/120 V panel and reports the demand per phase.