If the neutral and ground wires are bonded at the sub-panel, any fault current on the ground wire could travel along the grounded parts of the electrical system, including metal parts like conduit, electrical boxes, and even appliances. This poses a risk of electric shock to anyone who comes into contact with these surfaces, even if the electrical system appears to be properly grounded.

In a properly wired system, the neutral wire serves as the return path for electrical current, while the ground wire is only intended for safety purposes, providing a path for fault current to return to the earth. When these wires are bonded inappropriately at the sub-panel, it can create improper current flow, causing the neutral wire to carry more current than it is designed to handle. This can lead to overheating of wires, circuit breakers tripping, or even fire hazards.

When the neutral and ground are bonded at the sub-panel, the grounding system might be forced to carry return current from the neutral. This can overwhelm the ground wire and grounding system, leading to overheating or failure of ground connections. In the event of a fault, this can result in unsafe conditions.

According to the National Electrical Code (NEC), neutral and ground wires should only be bonded in the main service panel (also known as the main disconnect panel). In a sub-panel, the neutral and ground should be kept separate to ensure the proper operation of the electrical system. Bonding them in the sub-panel is a violation of electrical codes and could result in failed inspections or penalties.

When the neutral and ground conductors are incorrectly bonded at the sub-panel, the additional current flowing through the ground conductor can cause excessive heating. This can lead to degradation of insulation, wire damage, or even fires.

Open the sub-panel and inspect the neutral bar and the ground bar. If they are physically connected (bonded), this indicates that neutral and ground wires are improperly bonded. In a properly wired sub-panel, the neutral bar and ground bar should not be connected. The neutral bar should only carry neutral wires, and the ground bar should only carry ground wires.

In a properly installed sub-panel, there should be a separate ground rod or ground connection at the sub-panel. If the ground is improperly bonded to the neutral, it may indicate an issue with the wiring that could lead to hazardous conditions.

Using a voltage tester or multimeter, you can check the voltage between the ground and neutral bars. If there is a voltage present, this indicates that the neutral and ground are improperly bonded at the sub-panel, as no voltage should be present between these two points in a correctly wired system.

If you notice that breakers are frequently tripping or if certain appliances or devices are malfunctioning, this could be a sign of improper bonding between the neutral and ground conductors, leading to overloaded circuits or ground faults.

The first step in correcting this issue is to separate the neutral and ground bars in the sub-panel. This may involve installing an insulating barrier that isolates the neutral bar from the ground bar, ensuring that they are not physically connected.

In some cases, it may be necessary to install separate ground and neutral bars in the sub-panel if they are not already present. The neutral bar should be used exclusively for neutral conductors, and the ground bar should only carry the ground wires.

Ensure that the neutral wire is properly connected to the neutral bus bar in the sub-panel, and the ground wire is connected to the ground bus bar. These connections should be secure and free from any loose or damaged wiring.

Verify that the neutral and ground are properly bonded in the main service panel (main disconnect panel), as required by electrical codes. The bonding should only occur in the main panel, not in any sub-panels downstream.

If you are unsure about how to correct the bonding issue or if the work involves more complex wiring adjustments, it is highly recommended to consult a licensed electrician. They can ensure that the sub-panel is properly wired according to electrical codes, preventing potential safety hazards.

Always adhere to the National Electrical Code (NEC) and local regulations when installing or modifying electrical systems. Neutral and ground conductors must be correctly separated at sub-panels, and any work should be inspected to ensure compliance with safety standards.

Use appropriate grounding materials and ensure that the electrical panel is properly installed with clear separation between neutral and ground bars. Avoid using makeshift or incorrect solutions that may lead to bonding issues.

Schedule routine inspections of your electrical system, including the main and sub-panels, to ensure that neutral and ground wires are properly separated and that all connections are secure and safe.

If you are an electrician or contractor, make sure to educate all team members about the proper installation techniques for separating neutral and ground conductors in sub-panels. Proper training helps prevent common mistakes and ensures the system is safe for use.