New York State Master Electrician Practice Exam

How many 20A branch circuits are needed for 80 linear feet of show window lighting space?

1. 5 circuits

2. 7 circuits

3. 9 circuits

4. 11 circuits

The correct answer is: 9 circuits

To determine the number of 20A branch circuits required for 80 linear feet of show window lighting space, it's essential to understand the electrical load that will be placed on each circuit and the lighting requirements for such an area. In commercial setups, the National Electrical Code (NEC) suggests a general guideline for lighting circuits. For general illumination, a common rule of thumb is to allocate about 3 watts per linear foot of show window lighting. Therefore, for 80 linear feet, you would calculate the total wattage as follows: 80 linear feet x 3 watts/foot = 240 watts. Next, since each circuit can handle a specific load, you need to consider the capacity of a 20A circuit. The formula to calculate the maximum wattage for a circuit is: Watts = Volts x Amperes. For standard circuits in the U.S., the voltage is typically 120 volts. Thus, for a 20A circuit: Watts = 120 volts x 20 amps = 2400 watts. This means that a single 20A circuit can handle significantly more than the total wattage required for the show window lighting. However, it's advisable to utilize only 80% of the circuit's capacity for