Licensed Electrical Contractor Licensed Electrical Contractor Branch Circuit Calculations Questions and Answers 3

Question 1

A 240V, single-phase branch circuit supplies three 1,200W baseboard heaters. What minimum branch circuit rating is required when treated as a continuous load?

Accepted Answer

25 amperes

Answer

The total load is 3,600W at 240V drawing 15A, and applying the 125% continuous load factor requires a minimum 18.75A rating, so a 25A circuit is needed.

Question 2

According to NEC Table 210.24, what is the maximum cord-and-plug-connected load permitted on a 20-ampere branch circuit?

Accepted Answer

16 amperes

Answer

NEC Table 210.24 limits a single cord-and-plug-connected load to 80% of the branch circuit rating, which is 16 amperes for a 20A circuit.

Question 3

When sizing a branch circuit for a 9,600W household electric range at 240V using NEC Table 220.55 Column C, what is the maximum demand load?

Accepted Answer

8,000 watts

Answer

NEC Table 220.55 Column C permits a maximum demand of 8,000 watts for a single household range rated up to 12 kW.

Question 4

A 120/240V branch circuit panel has a two-pole 30A breaker feeding a dryer circuit. What is the maximum VA capacity of this circuit?

Accepted Answer

7,200 VA

Answer

A 30A circuit at 240V provides a maximum capacity of 7,200 VA (30A x 240V).

Question 5

Per NEC 210.52(C), countertop receptacles in a dwelling kitchen must be supplied by a minimum of how many branch circuits?

Accepted Answer

2

Answer

NEC 210.52(C) requires that kitchen countertop receptacles be served by at least two small-appliance branch circuits.

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Licensed Electrical Contractor Licensed Electrical Contractor Branch Circuit Calculations Questions and Answers 3