Licensed Electrical Contractor Load Calculation and Services 5

Question 1

A 240V, single-phase service feeds six electric water heaters, each rated at 4,500 W. What demand factor applies per NEC 220.53?

Accepted Answer

75%

Answer

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.

Question 2

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?

Accepted Answer

NEC 230.70(A)(1)

Answer

NEC 230.70(A)(1) requires the service disconnect to be installed at a readily accessible location nearest the point of service entrance.

Question 3

A 1,200-ampere service is calculated for a large commercial building. Per NEC 230.79, is this service rating permitted?

Accepted Answer

Yes — no maximum service size is specified in NEC 230.79

Answer

NEC 230.79 only establishes minimum service ratings; there is no NEC maximum, so a 1,200A service is permitted.

Question 4

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?

Accepted Answer

80%

Answer

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).

Question 5

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?

Accepted Answer

200-ampere service

Answer

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.

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Load Calculation and Services 5