Choosing the Right Wire Size for Powering a Wall/Fence with 50 Light Posts

When powering a wall or fence with 50 light posts, selecting the right wire size is crucial for both safety and efficiency. This article will guide you through the process of calculating total power requirements, determining current load, and choosing the appropriate wire size based on your specific setup.

Calculating Total Power Requirement

To determine the correct wire size, we first need to calculate the total power required to light the 50 light posts. The bulbs can be classified into two categories: 150-watt bulbs and 20-watt LED bulbs. Let's explore three scenarios:

All 150-watt bulbs:

Total Power 50 bulbs × 150 watts 7,500 watts

All 20-watt LED bulbs:

Total Power 50 bulbs × 20 watts 1,000 watts

Mixed setup (25 bulbs at 150 watts and 25 bulbs at 20 watts):

Total Power 25 × 150 25 × 20 3,750 500 4,250 watts

Calculating Total Current

Next, we need to calculate the current using the formula:

Power (W) Voltage (V) × Current (A)

Assuming a standard voltage of 120V, we can find the current for each scenario:

Scenario 1: 7,500 watts

Current 7500 W / 120 V ≈ 62.5 A

Scenario 2: 1,000 watts

Current 1000 W / 120 V ≈ 8.33 A

Scenario 3: 4,250 watts

Current 4250 W / 120 V ≈ 35.42 A

Selecting the Appropriate Wire Size

The appropriate wire size depends on the current and the distance from the power source to the light posts. Here are some general guidelines for copper wire based on the current calculated:

8.33 A (1000 watts)

1.5 mm2 is typically sufficient.

35.42 A (4250 watts)

6 mm2 is typically recommended.

62.5 A (7500 watts)

10 mm2 is typically necessary.

Conclusion

Based on the scenarios outlined:

If you are using only 150-watt bulbs, you should use 10 mm2 wire for optimal performance and safety. If you are using only 20-watt LED bulbs, a 1.5 mm2 wire is adequate. For a mixed setup, it’s safer to use 6 mm2 wire, especially if you anticipate running close to the maximum current at any point.

Always consider local electrical codes and regulations and consult with a qualified electrician for the final decision on wire sizing based on your specific installation details.