Understanding Panel Bond Screw Sizes: 8 To The Power Of 10

Bonding screws are used to connect the neutral and ground wires in a main electrical panel. The grounding screw is not used in sub-panels, where the neutral and ground wires are kept separate. The grounding bar in most panels is already bonded to the case. The grounding screw is used to connect the neutral and ground wires together, but only in a main panel. In sub-panels, the neutral and ground wires are isolated.

Screw size variety for different Square D panels

Square D panels come in a variety of sizes and types, and so do the screws that go with them. The screw size will depend on the specific Square D panel you have. Here are some common screw sizes and types for different Square D panels:

QO and Homeline Load Centers

Square D QO and Homeline load centers typically use #10 or #12 sheet metal screws. These screws have a course thread and are designed to fit into the spring metal clips over the holes in the panel. The replacement screws for these panels are usually sold in packs of six and can be found at most hardware stores or online.

Older QO Load Centers

For older QO load centers, you may need a different type of screw. The original screws that came with these panels are known to have a unique thread pattern, making it difficult to find an exact match. In this case, you may need to use a tap to create your own threads or find a similar screw that will fit.

GE Bonding Screw

If you are looking for a bonding screw for a Square D panel, the GE Bonding Screw TBS is a commonly used option. This screw is designed for use with powermark gold load centers and can be found at hardware stores or online.

Panel Cover Screws

Square D panel cover screws, such as the Square D by Schneider Electric S106, are typically smaller and have dimensions of approximately 0.55 x 0.55 x 0.94 inches. These screws are used to secure the cover of the load center and are often sold in packs of six as well.

It is important to identify the specific Square D panel you are working with to select the correct screw size and type. Always refer to the manufacturer's instructions or consult with a professional if you are unsure about the appropriate screw for your panel.

Grounding and bonding

Understanding the Basics

Electricity always seeks the path of least resistance to reach the ground, which can be through appliances, motors, lightbulbs, or any other powered device. When a fault occurs, the closed circuit is broken, and electricity looks for an alternative route to the ground. This is where grounding and bonding come into play, providing a safety net to guide electricity back to the ground and prevent hazards.

Grounding

Grounding involves creating a physical wiring path that allows electricity to reach the earth in case of a fault. It includes connecting electrical equipment and appliances to the electrical source, reducing the risk of shock or electrical fires. Grounding provides a safe route away from people and appliances, directing electricity through a neutral wire to a drain-off point, completing the circuit.

Ground wires are typically made of bare copper or copper with green insulation and possibly a yellow stripe. They become active during a surge, fault, or overcurrent situation, carrying electricity to a bus bar and then out through the neutral line to complete the circuit.

Bonding

Bonding works alongside grounding by connecting metallic objects that may encounter electrical faults to the grounding neutral. During a fault, bonding helps trip the breakers quickly and provides a path for static electricity and induced voltages to drain safely.

When establishing bonding connections, conductors must be sized to handle the largest load expected during a fault. Bonding is commonly used for metallic connectors, boxes, enclosures, pipes, machinery, and exposed electronics.

The Importance of Bonding and Grounding

Bonding and grounding are crucial for safety. By bonding materials to a ground system, faults are contained, and electricity is safely drained from affected appliances and machines. This also prevents dangerous shocks, protecting individuals who may come into contact with faulty equipment.

While bonding and grounding have distinct differences, they work together to prevent accidents, fires, and shocks. Understanding when and how to implement bonding and grounding ensures the safety of electrical systems.

Main panel vs subpanel

Understanding the electrical system in your home is important to safeguard your appliances and property from potential power surges and electrical fires. The main panel and sub-panel play a crucial role in this regard, and it is essential to know the differences between them.

The main panel, also known as the electrical breaker box, is the primary hub for electricity in your home. It is the first point of connection for power from the utility company and acts as the first line of defence against electrical surges. This panel includes a main switch that allows you to connect and disconnect power. It provides power, controls power, and regulates power distribution throughout your home. The main panel is the only point where you can disconnect your home entirely from the power grid. It is typically installed inside a business or home and requires professional installation due to safety concerns.

A sub-panel, on the other hand, is an additional control centre that distributes power to different areas within your property. It acts as an intermediary between the circuits in your property and the main panel. The sub-panel receives its power from the main panel and does not independently supply energy to a house. It is similar to the main panel in that it also has a breaker at each end to prevent electrical overloads and protect your appliances and property from potential damage. Sub-panels are often installed when additional circuits are needed, such as for a home addition, a detached garage, or high-demand appliances. They provide flexibility and allow for efficient energy distribution by dividing power into multiple smaller circuits.

One key distinction between the main panel and the sub-panel is their connection to the power source. The main panel is directly linked to the entrance point of the house and receives power directly from the utility company. In contrast, the sub-panel operates off the power provided by the main panel. Sub-panels are usually placed outside the building, providing a safety advantage in case of emergencies. They also offer more space for electrical distribution and convenience in accessing circuit breakers.

When deciding whether to install a sub-panel, it is important to consider the current load distribution and any recent increases in power requirements. Consulting with a professional electrician is recommended to ensure compliance with safety regulations and to choose the right sub-panel size.

Safety issues with improper subpanel bonding

Improper subpanel bonding can lead to several safety issues, and it is important to understand the difference between a main panel and a subpanel, and how they are wired.

Main Panel vs Subpanel

A main panel is the area where you have complete control over the power within your home. It contains the main "service disconnect" (i.e. shut-off). A subpanel, on the other hand, has its own breaker switches but not the main. These typically control specific rooms or appliances in your home or other buildings on your property. Not all homes have subpanels, and if you have one, it is usually located in the garage.

Wiring

Both the main panel and the subpanel contain four types of wires: two hot wires (black or red casing), one neutral wire (white casing), and one ground wire (green casing or bare metal wire, usually copper or aluminum). The hot wires carry energy to a fixture (e.g. a wall plug or stove). The neutral wires then carry the energy (current/amperage) from those circuits back to the panel, completing the electric circuit and generating power.

Ground Wire

The ground wire is a safety feature. Hot and neutral wires are dangerous as they constantly run electricity through them. Frayed wiring cords or loose wire connections can cause these wires and their electrical currents to mix, leading to short circuits, sparks, and fires. The ground wire prevents this by sending all faulty electrical currents back to the source or the ground.

Improper Subpanel Bonding

The ground and neutral wires must be bonded (or connected) together, but this is only allowed in the main panel, never in a subpanel or anywhere else in the home. This is a very common mistake, even made by some "professionals," but it is usually a sign of amateur electrical work.

In the main panel, the neutral wire is connected to the bus bar, and further down that bus bar is a screw or strap that "bonds" it to the metal bar that leads to the left side of the panel, where the ground wires (also known as the EGC/GEC's) are located. This effectively bonds the neutral and ground together in the same service enclosure.

In the subpanel, however, the neutral wires are not bonded to the ground wires. They both have their own individual paths. If the ground and neutral wires are bonded in the subpanel, it gives the neutral wire multiple pathways, which can lead to equipment chassis becoming energized. This can result in shocks and house fires.

Improper subpanel bonding can lead to serious safety issues, including shocks and house fires. It is important to ensure that the ground and neutral wires are only bonded in the main panel and that the subpanel wiring is left to qualified electricians.

Qualified electricians for subpanel work

Adding a subpanel to your electrical system is a complex process that requires careful consideration and expertise. Here's why you should hire qualified electricians for subpanel work:

Electrical Expertise

Qualified electricians have the necessary training and experience to handle subpanel installations safely and effectively. They understand the complex electrical system in your home or building and can ensure that the subpanel is installed correctly. This includes making sure that the subpanel is properly connected to the main electric panel, which can be a challenging task for those unfamiliar with electrical work.

Safety

Working with electricity can be dangerous, and it is always best to leave it to the professionals. Qualified electricians will follow strict safety protocols to protect your home and family during the installation process. They will also ensure that your electrical system meets local building codes and safety standards, giving you peace of mind.

Load Calculations

When adding a subpanel, it is crucial to consider the electrical load requirements of your property. Qualified electricians can assess your current and future electrical needs and recommend the appropriate subpanel size and breaker combination. They will ensure that your electrical system can handle the additional load without overloading the overall system.

Proper Wiring

One of the most important aspects of subpanel installation is proper wiring. Qualified electricians will plan and execute the wiring process with precision, ensuring that the wires are routed neatly and securely. They will also make sure that the correct types of wires and cables are used, depending on the amperage and distance between the main panel and the subpanel.

Troubleshooting and Maintenance

Qualified electricians can provide ongoing support and maintenance for your electrical system, including the subpanel. They can troubleshoot any issues that may arise and perform repairs or replacements as needed. This ensures that your electrical system remains safe and reliable over the long term.

In summary, hiring qualified electricians for subpanel work is essential to ensure the safety and functionality of your electrical system. Their expertise, experience, and adherence to safety standards will give you peace of mind and help protect your property. While it may be tempting to attempt a DIY installation, the potential risks and complexities involved make it a job best left to the professionals.

Frequently asked questions