Free TN-LLE Commercial Load Calculations Questions and Answers 1

Question 1

What is the calculated general lighting load for a 20,000 sq. ft. office building after applying all applicable demand factors?

Accepted Answer

41,250 VA

Answer

First, calculate the total lighting VA: 20,000 sq. ft. x 3.5 VA/sq. ft. (Table 220.12) = 70,000 VA. Then, apply demand factors from Table 220.42: the first 12,500 VA is at 100%, and the remainder (57,500 VA) is at 50%. The final calculated load is 12,500 VA + (57,500 VA x 0.50) = 41,250 VA.

Question 2

A commercial occupancy has 100 general-purpose duplex receptacles. What is the calculated load for these receptacles after applying demand factors?

Accepted Answer

14,000 VA

Answer

Per NEC 220.14(I), each receptacle outlet is calculated at 180 VA. The total connected load is 100 outlets x 180 VA = 18,000 VA. According to NEC 220.44, the first 10 kVA (10,000 VA) is taken at 100%, and the remainder (8,000 VA) is at 50%. The calculated load is 10,000 VA + (8,000 VA x 0.50) = 14,000 VA.

Question 3

What is the calculated load for 40 linear feet of show-window lighting in a retail store?

Accepted Answer

8,000 VA

Answer

NEC 220.14(G) requires that show-window lighting be calculated at a minimum of 200 VA per linear foot. Therefore, the total calculated load is 40 ft x 200 VA/ft = 8,000 VA. This load is added to the general lighting load before general lighting demand factors are applied.

Question 4

A commercial kitchen contains 5 pieces of permanently installed cooking equipment with a total nameplate rating of 60 kW. What is the calculated demand load for this equipment?

Accepted Answer

42 kW

Answer

NEC 220.56 and the associated Table 220.56 allow for a demand factor to be applied to commercial kitchen equipment. For 5 appliances, the demand factor is 70%. The calculated load is 60 kW x 0.70 = 42 kW.

Question 5

A 4-wire, 3-phase, 208Y/120V system serves a non-linear load with a calculated maximum unbalanced current of 250A. What is the calculated demand load on the neutral conductor?

Accepted Answer

235A

Answer

According to NEC 220.61(C), a demand factor of 70% can be applied to the portion of the unbalanced load exceeding 200A. The first 200A is calculated at 100%. The calculation is: 200A + ((250A - 200A) x 0.70) = 200A + (50A x 0.70) = 200A + 35A = 235A.

TN LLE - Tennessee Limited Licensed Electrician Practice Test

TN LLE - Tennessee Limited Licensed Electrician Practice Test

Free TN-LLE Commercial Load Calculations Questions and Answers 1