Licensed Electrical Contractor Load Calculation and Services 2 — Questions and Answers
Question 1: When applying the optional calculation method for a dwelling unit, what is the minimum load in volt-amperes applied to the first 10 kVA of all other loads?
- 80%
- 100% (Correct answer)
- 40%
- 125%
Correct answer: 100%
Under NEC 220.82, the first 10 kVA of all other loads is calculated at 100%, with the remainder at 40%.
Question 2: A 240V, single-phase service feeds a 10 kW electric range. Using the standard calculation method, what demand load from NEC Table 220.55 applies for one range?
- 8 kW (Correct answer)
- 10 kW
- 12 kW
- 6 kW
Correct answer: 8 kW
NEC Table 220.55, Column C specifies an 8 kW demand for a single household range rated up to 12 kW.
Question 3: What is the minimum size service required for a single-family dwelling under NEC 230.79?
- 60 amperes
- 100 amperes (Correct answer)
- 150 amperes
- 200 amperes
Correct answer: 100 amperes
NEC 230.79(C) requires a minimum 100-ampere, 3-wire service for a single-family dwelling.
Question 4: When calculating feeder neutral load for a residential service, how is the unbalanced load between lines reduced per NEC 220.61?
- The neutral is sized at 100% of the maximum unbalanced load
- The portion of neutral load above 200A may be reduced by 70% (Correct answer)
- The neutral load is always equal to the phase load
- The neutral load is reduced by 25% for all loads
Correct answer: The portion of neutral load above 200A may be reduced by 70%
NEC 220.61(B)(1) permits the neutral load above 200A to be multiplied by 70% for further reduction.
Question 5: A commercial occupancy has 50,000 VA of receptacle load. What demand factor applies to the receptacle load above 10,000 VA per NEC Table 220.44?
- 100%
- 75%
- 50% (Correct answer)
- 25%
Correct answer: 50%
NEC Table 220.44 allows the receptacle load exceeding 10,000 VA to be calculated at 50% demand.
Question 6: Which NEC article governs services, including the number of service disconnects permitted?
- NEC Article 215
- NEC Article 225
- NEC Article 230 (Correct answer)
- NEC Article 240
Correct answer: NEC Article 230
NEC Article 230 covers services, including the rule that no more than six disconnecting means are permitted.
Question 7: When sizing a service for a building with multiple HVAC units, how are the hermetic refrigerant motor-compressor loads treated per NEC 440.6?
- At 80% of full-load current
- At 125% of the largest motor plus 100% of all others
- At the rated-load current or branch-circuit selection current, whichever is greater (Correct answer)
- At 75% of nameplate current
Correct answer: At the rated-load current or branch-circuit selection current, whichever is greater
NEC 440.6 requires using the rated-load current or branch-circuit selection current (whichever is larger) as the load for each hermetic compressor.
Licensed Electrical Contractor Load Calculation and Services 2
When applying the optional calculation method for a dwelling unit, what is the minimum load in volt-amperes applied to the first 10 kVA of all other loads?