Bonding the neutral at a subpanel (also known as a downstream panel, or remote distribution panel) creates a dangerous situation called a parallel neutral path. Here's why

The Fundamental Issue: Parallel Current Paths
Proper Wiring

In a properly wired system, the only place the neutral conductor should be bonded to the ground (equipment grounding conductor) is at the

main service entrance (where the power enters the building from the utility). The Problem

When you bond the neutral to the ground at the subpanel, you create a second path for neutral current to return to the source (the main panel/transformer). Now, neutral current can flow through both the neutral conductor and the ground conductor (equipment grounding conductor).

The Dangers of Parallel Neutral Paths1. Overloaded Grounding Conductors

The ground wire is designed to carry fault current (current from a short circuit) back to the source to trip a breaker or fuse. It's not designed to carry continuous neutral current. If the ground wire carries neutral current continuously, it can:

Overheat

The ground wire may be too small to handle the normal neutral current. Overheating can melt insulation, create a fire hazard, and potentially damage equipment.

Reduce Grounding Effectiveness

If the ground wire is already carrying neutral current, its ability to quickly and effectively carry fault current is compromised. This can slow down breaker tripping times, increasing the risk of electrical shock.2.

Electromagnetic Fields (EMF)

When current flows through both the neutral and ground wires, it can create elevated EMF levels in the surrounding area. While the health effects of EMF are still debated, many people prefer to minimize their exposure.3.

Nuisance Tripping

In some cases, the imbalance created by the parallel neutral path can cause GFCI (Ground Fault Circuit Interrupter) breakers to trip unnecessarily.4.

Increased Risk of Electrical Shock

Because metal enclosures connected to the grounding system could now be carrying neutral current, you could get an electrical shock if you touch a grounded metal object and a live wire. This is especially dangerous in damp or wet environments.5.

Incorrect Voltage Readings

The parallel neutral path can cause voltage readings to be unstable or inaccurate, making troubleshooting difficult.

How to Prevent Bonding the Neutral at a Subpanel1. Use a 4-Wire Feed

Run a 4-wire feeder from the main panel to the subpanel: Two hot wires (e.g., L1 and L2) One neutral wire One separate equipment grounding conductor (EGC) – typically a bare or green wire2.

Isolate the Neutral Bus

At the subpanel, the neutral bus bar must be isolated* from the panel enclosure (and any other grounded metal parts). Typically, this is done by using insulated standoffs. Remove any bonding screws or straps that connect the neutral bus to the enclosure.3.

Connect the Ground Wire Properly

Connect the equipment grounding conductor to a separate ground bus bar that is bonded to the subpanel enclosure.

In Summary

Bonding the neutral at a subpanel is a serious electrical code violation and creates a dangerous situation. The correct wiring method is to use a 4-wire feed and keep the neutral isolated at the subpanel, relying on a separate equipment grounding conductor for safety. If you are not completely comfortable with electrical wiring, hire a qualified and licensed electrician to perform the work. Improper wiring can be deadly. Flag for review