Load Calculation and Services Flashcards
7 cards from real Licensed Electrical Contractor practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Load Calculation and Services flashcards as text
A 240V, single-phase service feeds six electric water heaters, each rated at 4,500 W. What demand factor applies per NEC 220.53?
Answer: 75%
NEC 220.53 allows a 75% demand factor when four or more fixed appliances (other than dryers, ranges, A/C, heat) are on the same feeder or service.
Which NEC section requires the service disconnecting means to be located at a readily accessible location either outside or inside nearest the point of entry?
Answer: NEC 230.70(A)(1)
NEC 230.70(A)(1) requires the service disconnect to be installed at a readily accessible location nearest the point of service entrance.
A 1,200-ampere service is calculated for a large commercial building. Per NEC 230.79, is this service rating permitted?
Answer: Yes — no maximum service size is specified in NEC 230.79
NEC 230.79 only establishes minimum service ratings; there is no NEC maximum, so a 1,200A service is permitted.
For a continuous load, service or feeder conductors must be sized so that the calculated load does not exceed what percentage of the conductor's ampacity before applying correction or adjustment factors?
Answer: 80%
NEC 215.2(A)(1) and 230.42 require that continuous loads not exceed 80% of the conductor's ampacity (or the overcurrent device rating).
A service calculation yields a total demand of 175 amperes for a single-family home. Per NEC 230.79, what is the minimum service size that must be installed?
Answer: 200-ampere service
Because NEC 230.79 sets 100A as the minimum and 175A exceeds standard 150A panels, a 200A service is the next standard size that meets or exceeds 175A.
Per NEC Table 220.12, what is the general lighting unit load for a hospital (volt-amperes per square foot)?
Answer: 3.5 VA/sq ft
NEC Table 220.12 assigns hospitals a unit load of 2.0 VA per square foot for general lighting calculations.
When using the standard calculation method for a multi-family dwelling, what demand factor per NEC Table 220.42 applies to lighting loads exceeding 120,000 VA?
Answer: 25%
NEC Table 220.42 applies a 25% demand factor to the portion of dwelling lighting loads exceeding 120,000 VA.