CME Advanced Load Calculations 3 — Questions and Answers
Question 1: When applying demand factors to a 50-unit apartment building's general lighting load per NEC Table 220.42, what demand factor applies to the portion of load from 120,001 VA and above?
- 100%
- 45%
- 35% (Correct answer)
- 25%
Correct answer: 35%
NEC Table 220.42 applies 35% demand factor to the remainder of the lighting load above 120,000 VA in dwelling units.
Question 2: A 200A, 240V single-phase service feeds a dwelling. Using NEC 220.82 optional method, the first 10 kVA of total connected load is counted at what percentage?
- 40%
- 80%
- 100% (Correct answer)
- 125%
Correct answer: 100%
Under NEC 220.82 optional method, the first 10 kVA of all connected load is counted at 100%.
Question 3: A commercial kitchen has five 5 kW commercial cooking units. Per NEC Table 220.56, what demand factor applies?
- 100%
- 80%
- 70% (Correct answer)
- 65%
Correct answer: 70%
NEC Table 220.56 for 5 cooking units in commercial occupancies applies a 70% demand factor.
Question 4: Per NEC 220.87, when determining the existing load on a service being upgraded, the maximum demand data must cover a minimum period of:
- 7 days
- 14 days
- 30 days (Correct answer)
- 60 days
Correct answer: 30 days
NEC 220.87 requires that maximum demand data be based on a minimum 30-day period to determine existing load.
Question 5: For a 240V, 1-phase, 10 kW fixed electric space heater, what is the minimum circuit ampacity required per NEC 424.3(B)?
- 41.67 A
- 52.08 A (Correct answer)
- 62.5 A
- 50 A
Correct answer: 52.08 A
Fixed electric space heaters are considered continuous loads; 10,000 W / 240 V = 41.67 A × 125% = 52.08 A minimum ampacity.
Question 6: In a 480/277V, 3-phase, 4-wire system, what is the calculated line-to-neutral voltage used for lighting load calculations?
- 208 V
- 240 V
- 265 V
- 277 V (Correct answer)
Correct answer: 277 V
In a 480/277V wye system, 480V ÷ √3 = 277V, which is the line-to-neutral voltage used for single-phase lighting loads.
Question 7: A warehouse has 80,000 sq ft of storage space. Using NEC Table 220.12, the general lighting unit load for storage warehouses is:
- 0.25 VA/sq ft (Correct answer)
- 0.5 VA/sq ft
- 1.0 VA/sq ft
- 2.0 VA/sq ft
Correct answer: 0.25 VA/sq ft
NEC Table 220.12 lists storage warehouses at 0.25 VA per sq ft for general lighting load calculations.
CME Advanced Load Calculations 3
When applying demand factors to a 50-unit apartment building's general lighting load per NEC Table 220.42, what demand factor applies to the portion of load from 120,001 VA and above?