You've hit on a complex and often misunderstood area of electrical work, especially when dealing with portable generators and DIY installations. Here's a breakdown of the core issues and considerations, as well as arguments for both sides, and a potential path forward

The Core Problem: Bonded vs. Floating Neutrals in Generators

The heart of the debate revolves around whether the neutral conductor in a portable generator's output is bonded to the generator's frame. Bonded Neutral

In this configuration, the neutral conductor is electrically connected (bonded) to the generator's frame, which is typically made of steel. This makes the frame effectively part of the neutral return path.

Floating Neutral

In this case, the neutral conductor is not bonded to the frame. It's electrically isolated.

The Code (NEC) Perspective (In the US)

The NEC (National Electrical Code) provides guidance on portable generators, primarily addressing situations where they are used to supply premises wiring systems (e.g., powering a house during an outage).

NEC 250.34(A): Separately Derived Systems

If the generator is used to power a building's wiring system through a transfer switch (and the generator is not connected through a cord and plug), the generator is considered a "separately derived system" (SDS). In this case, the NEC requires the generator's neutral to be bonded to the generator frame at the generator if it is powering through a manual/automatic transfer switch and the main is off. The grounding electrode conductor system of the building is then required to be connected to the generator frame. The NEC also describes certain circumstances where the neutral may not be bonded to the generator frame at the generator (250.34(B)). This is where the confusion comes from because, in order to understand whether that specific portion of code applies, you need to know the specific use case, which is often the part that DIYers have the most trouble with.

NEC 250.30(A)(1): Grounding Electrode Conductor

This section reinforces that a grounding electrode conductor (GEC) must be connected from the generator's frame to a grounding electrode (like a ground rod) when it's serving as an SDS.

NEC 250.34(C): Generator used on construction sites

This section says that generators used on construction sites only need to be grounded to the equipment grounding conductors through the cord-and-plug that supply receptacles mounted on the generator, provided that certain conditions are met, such as the generator is not supplying a fixed wiring system.

Why the Code Often Requires Bonding (or at least considers it the default)



Fault Current Path

The primary goal is to provide a low-impedance path for fault current. If a fault occurs (e.g., a hot wire touches the frame), the fault current needs a clear path back to the source (the generator) to trip a circuit breaker or GFCI. A bonded neutral and frame provides that path.

Safety in Single-Load Situations

For single-load situations (e.g., powering a single appliance directly from the generator), a bonded neutral provides a more reliable ground fault path.

Why DIYers Break the Bond (or why they think they should)

This is where the trouble starts. DIYers often incorrectly interpret the code or listen to misinformation. The primary reasons they cite for breaking the bond include:

Misunderstanding of Transfer Switches

Many believe that if they are using a transfer switch, that it will handle the grounding and bonding. This is false.

"Neutral-Ground Bond in Multiple Locations is Bad"

The idea that having multiple neutral-ground bonds will cause circulating currents in the grounding system is generally correct. However, the application of this idea to portable generators is often wrong.

"It's Safer if It's Floating"

This is a dangerous misconception. A floating neutral can actually increase the risk of electric shock in some fault scenarios because there's no reliable path for fault current to flow, and the chassis will float, which is not desired.

Your Concerns About Steel Frames

You're right to be concerned about the potential hazard of a steel frame on a generator, especially if it's not properly grounded. If the frame is not bonded to the neutral (and then grounded), and a hot wire comes into contact with the frame, the frame can become energized and pose a shock hazard.

Why Utility Services Don't Have a Grounding Conductor at the Source (Transformer)

You're correct that the utility doesn't run a grounding conductor with the primary distribution lines. Here's why:

Redundancy

The neutral conductor is grounded at the transformer (where the service originates). The neutral is also grounded at the customer's service entrance.

Cost

Running a separate grounding conductor for miles would be incredibly expensive.

Earth as a Fault Path

Utilities use the earth as a fault current path, but it's not a reliable, low-impedance path like a dedicated grounding conductor.

Multiple Grounds

The neutral wire is grounded many times throughout the entire system.

Inverter Generators vs. Induction Generators



Inverter Generators

Often have floating neutrals because they use electronic inverters to generate the AC power. The inverter output is often isolated.

Induction Generators

Typically have bonded neutrals because they directly use a rotating magnetic field to induce voltage in the output windings.

The Problem with Running a Grounding Conductor with Generators and Cords



Potential for Ground Loops

If you have a bonded neutral at the generator and a grounding conductor running with the cord that is then connected to a grounded receptacle, you're creating a potential ground loop. This can cause circulating currents in the grounding system, which can lead to nuisance tripping of GFCIs, humming in audio equipment, and even overheating of conductors in extreme cases.

Cord as Primary Ground

The equipment grounding conductor (the green wire) in the cord is intended to be the primary ground fault path.

Arguments for Both Sides of the Bonded/Floating Neutral Debate



Arguments for Bonded Neutral



Fault Protection

Provides a low-impedance fault path for quick breaker tripping, enhancing safety, especially in single-load scenarios.

Voltage Stabilization

Can help stabilize the voltage output of the generator, reducing voltage fluctuations.

Code Compliance

Aligns with the NEC requirements for separately derived systems in many scenarios, provided it does not feed into a ground loop.

Arguments Against Bonded Neutral (or in favor of a floating neutral in specific cases)



Reduced Risk of Ground Loops

Prevents circulating currents that can arise from multiple neutral-ground bonds, potentially minimizing nuisance tripping and other electrical issues.

Safer for Certain Types of Sensitive Equipment

Some electronic equipment may be more susceptible to damage from ground loops.

Avoids Parallel Neutral-Ground Paths

If a generator with a bonded neutral is connected to a premises wiring system that already has a neutral-ground bond, you could create parallel paths for neutral current, which can overload the grounding conductor.

Improving Your Position and Recommendations


Emphasize the Importance of Understanding the Specific Use Case

The "right" answer depends entirely on how the generator is being used. Is it powering a single appliance? Is it powering a house through a transfer switch? Is it used on a construction site?2.

Prioritize Safety Above All Else

A safe installation is paramount. This often means erring on the side of providing a robust ground fault path.3.

Educate Your Customers (DIYers)

This is the most crucial step. Explain the risks and benefits of each configuration, and help them understand the code requirements relevant to their specific situation. This will require time and good questioning of the client.4.

Recommend a Qualified Electrician

If there's any doubt about the correct installation, strongly recommend that the customer consult with a qualified electrician who can assess the situation and ensure a safe and code-compliant installation.5.

Suggest the use of GFCI's

Using GFCI extension cords is a cheap and effective way of protecting against shock.6.

If Possible, Avoid Parallel Conductors to the Utility

That should be left to professionals.7.

If you are using a manual or automatic transfer switch, the generator must be considered a separately derived system and you should follow the code for that, as well as ensure there are no ground loops8. If the generator is not being used to power a premises wiring system through a transfer switch, then the conditions must be as described in NEC 250.34(C), so that a ground rod is not neededSummary Checklist to Guide Your Recommendations



Is the generator powering a building's wiring system through a transfer switch? If yes, it's likely an SDS, and a bonded neutral (at the generator) is generally required (with the building's grounding electrode system connected to the generator frame). Ensure there are no Ground Loops! Is the generator powering a single appliance or a few appliances directly via extension cords? In this case, a bonded neutral at the generator is generally safer, providing a good fault path. Is the generator an inverter type? If so, check the manufacturer's documentation to see if the neutral is already bonded internally. If not, consider whether bonding it is necessary based on the use case.

Important Considerations



Local Codes

Always check local electrical codes, as they may have specific requirements for portable generators.

Manufacturer's Instructions

Always follow the generator manufacturer's instructions regarding grounding and bonding.

Qualified Electrician

When in doubt, consult with a qualified electrician.

In conclusion, there's no one-size-fits-all answer to the bonded/floating neutral question. It depends on the specific application, the type of generator, and local codes. The most important thing is to prioritize safety and ensure that there's a reliable path for fault current to flow in the event of a fault. By educating yourself, understanding the principles involved, and communicating effectively with your customers, you can help them make informed decisions and ensure safe generator installations. Flag for review