OCPD Question

[deputygrsmith]

I am studying a sign question that has 1800VA x 125% = 2250VA /120V = 18.8a and requires a 20a OCPD (continuous load).

If a 20a OCPD has a max of 80% (16a), what NEC rule allows this 20a OCPD to protect 18.8a?

Thanks

 

[charlie b]

You already accounted for the 80% by having multiplied the actual load by 125%. The two numbers are reciprocals of each other. You could have done it in the other order. 1800VA/120V = 15 amps. 15 is lower than 16 (i.e., 80%of 20 amps), so it is acceptable.