Master Electrician Practice Exam

What is the demand load, in VA, for two 20-ampere, 120-volt branch circuits provided for exterior electric signs?

1. 1,500 VA

2. 2,000 VA

3. 2,500 VA

4. 3,000 VA

The correct answer is: 3,000 VA

To calculate the demand load for two 20-ampere, 120-volt branch circuits, you start by determining the total capacity of one branch circuit. The formula for calculating the load in volt-amperes (VA) is: \[ \text{Load (VA)} = \text{Voltage (V)} \times \text{Current (A)} \] For a single circuit: \[ 120 \, \text{V} \times 20 \, \text{A} = 2,400 \, \text{VA} \] As there are two circuits, the initial thought might be to double that amount: \[ 2,400 \, \text{VA} \times 2 = 4,800 \, \text{VA} \] However, when calculating the demand load, you typically apply demand factors that take into account that not all circuits will be loaded to their maximum at the same time. According to the National Electrical Code (NEC), for branch circuits used for exterior signs and similar applications, considerable continuous loads are normally prepared using a demand factor to manage the overall expected load properly. For exterior electric signs, demand load calculations often use a demand factor of 0.