Here is the question:

"How many 120V, two wire, 20 ampere branch circuits are required to supply

52 parking lot lights, which are rated 500va each and are continuous loads?"


I am getting ~ 14, but the answer in the book is 18

Can you help?

Here is the question:

"How many 120V, two wire, 20 ampere branch circuits are required to supply

52 parking lot lights, which are rated 500va each and are continuous loads?"


I am getting ~ 14, but the answer in the book is 18

Can you help?
Dont you have to derate it ; you get 18

52 lights at 500 VA=26000 VA / 120 Volts = 216.67 total amps

A 15 amp circuit with a continuous load must be derated 80%, so the max load allowed on a 15 amp circuit is 12 amps.

216 / 12 = 18 circuits