Electrical Sub Panel Wiring Diagram: A Comprehensive Guide

Electrical sub panel wiring diagrams are essential for every residential and commercial building. It provides a clear understanding of the electrical system, how it works, and how it can be maintained. In this article, we will cover everything you need to know about electrical sub-panel wiring diagrams, including sub-panel types, installation, and troubleshooting.

What is an Electrical Sub Panel?

Before we dive into the wiring diagram, let’s first understand what an electrical sub-panel is. A sub-panel is a smaller panel that distributes power from the main electrical panel to different parts of the building. It is used when the main panel does not have enough space to accommodate additional circuits, or when there is a need to separate certain electrical loads.

Sub-panels can be installed in various locations, such as basements, garages, and outbuildings. They are also commonly used in commercial buildings to distribute power to different floors or sections of the building.

Types of Electrical Sub Panels

There are two main types of electrical sub-panels that you may encounter:

1. Main Lug Only (MLO) Sub Panel

A main lug only sub-panel does not have a main breaker installed. Instead, it is connected directly to the main panel, which provides the overcurrent protection. These sub-panels are typically used when the main panel is located nearby, and there is no need for additional disconnect switches.

The MLO sub-panel can be wired in a variety of ways, such as a 120-volt or 240-volt circuit. The wiring diagram for MLO sub-panels is relatively simple and straightforward, as there is no need to include a main breaker in the circuit.

2. Main Breaker Sub-Panel

A main breaker sub-panel, on the other hand, has a built-in main breaker that provides overcurrent protection. These sub-panels are typically larger than MLO sub-panels and are used when there is a need to separate specific electrical loads or when the main panel is located far away from the sub-panel.

The wiring diagram for a main breaker sub-panel is slightly more complex than an MLO sub-panel. It includes the main breaker, branch circuit breakers, neutral bus, and ground bus.

Electrical Sub Panel Wiring Diagram

Now that we understand the different types of sub-panels, let’s take a closer look at the wiring diagram. In this section, we will provide a step-by-step guide on how to wire an electrical sub-panel.

Step 1: Turn off Power

Before starting any electrical work, it is important to turn off the power to the main panel. This can be done by switching off the main breaker or by turning off the power supply from the utility company.

Step 2: Choose the Location

Choose the location where you want to install the sub-panel. Make sure that the location is easily accessible and that there is enough space to mount the sub-panel.

Step 3: Mount the Sub-Panel

Mount the sub-panel on the wall or other suitable location. Ensure that the sub-panel is level and plumb.

Step 4: Install the Cable

Install the cable from the main panel to the sub-panel. Use cable clamps to secure the cable in place. The size of the cable will depend on the amperage of the sub-panel and the distance between the main panel and the sub-panel.

Step 5: Install the Ground Wire

Connect the ground wire to the ground bus bar in the sub-panel. Make sure that the ground wire is properly attached and tightened.

Step 6: Install the Neutral Bar

Install the neutral bar in the sub-panel. The neutral bar should be securely mounted, and the neutral wires should be properly attached.

Step 7: Install the Breakers

Install the branch circuit breakers in the sub-panel. Make sure that the breakers are the correct size and that they are properly wired. The wiring diagram will indicate the correct wiring for each circuit.

Step 8: Connect the Load Wires

Connect the load wires to the breakers. The load wires should be properly connected to ensure that the circuit is complete and safe.

Step 9: Turn on Power

Once you have completed the wiring, turn on the power to the main panel. Test the sub-panel to ensure that it is working correctly.

Frequently Asked Questions (FAQ)

Question Answer
What size wire do I need for a sub-panel? The size of the wire will depend on the amperage of the sub-panel and the distance between the main panel and the sub-panel. Refer to the wiring diagram for the correct wire size.
Can I install a sub-panel myself? Yes, you can install a sub-panel yourself if you have the proper knowledge and experience. However, it is recommended that you hire a licensed electrician to ensure that the installation is safe and up to code.
What is the difference between an MLO sub-panel and a main breaker sub-panel? An MLO sub-panel does not have a main breaker installed, while a main breaker sub-panel has a built-in main breaker that provides overcurrent protection. The type of sub-panel you need will depend on your specific electrical requirements.
Can I add more circuits to a sub-panel? Yes, you can add more circuits to a sub-panel as long as you do not exceed the amperage rating of the sub-panel. Refer to the wiring diagram for the correct wiring of additional circuits.

Conclusion

Electrical sub-panel wiring diagrams are essential for every building that requires a reliable and safe electrical system. In this article, we have covered the different types of sub-panels, the installation process, and some common FAQs. Remember to always follow the wiring diagram and consult a licensed electrician if you are unsure about any aspect of the installation process.