CME Advanced Load Calculations 2 — Questions and Answers
Question 1: A 3,600 sq ft dwelling has a 12 kW range. Using the NEC Table 220.55 demand factor, what is the demand load for the range?
- 8,000 W
- 8,400 W (Correct answer)
- 10,800 W
- 12,000 W
Correct answer: 8,400 W
NEC Table 220.55 for a single range rated 12 kW (over 8.75 kW) uses Column C: 8 kW + 5% per kW over 12 kW, but for exactly 12 kW the demand is 8,400 W per the note (8 kW + 400 W).
Question 2: When calculating the demand load for electric dryers in a multi-family building with 25 units, which NEC table applies?
- Table 220.42
- Table 220.54 (Correct answer)
- Table 220.55
- Table 220.61
Correct answer: Table 220.54
NEC Table 220.54 provides demand factors for household electric dryers in multi-family and similar installations.
Question 3: A commercial building has a 200 kVA transformer supplying a 208Y/120V panel. What is the maximum continuous load in amps at 208V three-phase?
- 480 A
- 555 A (Correct answer)
- 960 A
- 1,108 A
Correct answer: 555 A
I = kVA × 1000 / (V × √3) = 200,000 / (208 × 1.732) = 200,000 / 360.3 ≈ 555 A.
Question 4: Per NEC 220.82, the optional calculation method for dwelling units applies when the service or feeder does NOT exceed:
- 100 amperes
- 150 amperes
- 200 amperes (Correct answer)
- 400 amperes
Correct answer: 200 amperes
NEC 220.82 optional method is available for dwelling units served by a single 3-wire, 120/240V or 208Y/120V service of 100 A or greater — the section covers existing or new 100 A+ services but is commonly applied up to 200 A service entries.
Question 5: A 480V, 3-phase motor has a nameplate full-load current of 40 A. What minimum feeder ampacity is required per NEC 430.22 for a single motor?
- 40 A
- 44 A
- 50 A (Correct answer)
- 52 A
Correct answer: 50 A
NEC 430.22 requires the feeder to be sized at 125% of the motor FLC: 40 A × 1.25 = 50 A.
Question 6: For a school building, NEC 220.14(H) specifies the unit load per outlet for receptacle outlets in general-use spaces as:
- 90 VA per outlet
- 120 VA per outlet
- 150 VA per outlet
- 180 VA per outlet (Correct answer)
Correct answer: 180 VA per outlet
NEC 220.14(H) specifies 180 VA per outlet for receptacle outlets in general-use spaces when the number of receptacles is not known.
Question 7: A 10,000 sq ft office building requires general lighting load calculation. Per NEC Table 220.12, the unit load for office occupancy is:
- 1.0 VA/sq ft
- 2.0 VA/sq ft (Correct answer)
- 3.5 VA/sq ft
- 5.0 VA/sq ft
Correct answer: 2.0 VA/sq ft
NEC Table 220.12 lists office buildings at 3.5 VA per sq ft for general lighting — confirming the correct answer is 3.5 VA/sq ft.
CME Advanced Load Calculations 2
A 3,600 sq ft dwelling has a 12 kW range.
Using the NEC Table 220.55 demand factor, what is the demand load for the range?