NEC Load Calculation Applications 3

Question 1

Per NEC 220.12, what is the minimum general illumination load in VA per square foot for a hospital?

Accepted Answer

2 VA/sq ft

Answer

NEC Table 220.12 lists hospitals at 2 VA per square foot for the general lighting load calculation.

Question 2

When calculating feeder load for fixed electric space heating under NEC 220.51, what percentage of the total connected heating load must be used?

Accepted Answer

100%

Answer

NEC 220.51 requires that 100% of the total connected fixed electric space heating load be included in feeder calculations with no demand factor reduction.

Question 3

A 400-ampere, 208Y/120V, three-phase service is installed. What is the calculated kVA capacity of this service?

Accepted Answer

144 kVA

Answer

Three-phase kVA = √3 × 208 V × 400 A ÷ 1000 = 1.732 × 208 × 400 ÷ 1000 ≈ 144 kVA.

Question 4

Under NEC 220.55, how many household cooking units must be on a single feeder before demand factors from Table 220.55 can be applied?

Accepted Answer

Two or more

Answer

NEC 220.55 allows demand factors from Table 220.55 to be applied when two or more single-phase household ranges are supplied by a three-phase feeder.

Question 5

What NEC section governs the calculation of feeder loads for marinas and boatyards?

Accepted Answer

553.12

Answer

NEC 553.12 provides the specific feeder and service load calculation requirements for floating buildings and marina receptacle loads.

NEC Practice Test

NEC Practice Test

NEC Load Calculation Applications 3