Read the manual thoroughly and understand all of the instructions, cautions, and warnings before using this equipment. If any section of the manual is not understood, contact your nearest authorized dealer, or contact Generac Customer Service at 1-888-436-3722 (1-888-GENERAC), or www.generac.com with any questions or concerns.  

 

Does my portable generator have a bonded or floating neutral?

It is important to understand whether a portable generator has a bonded or floating neutral. Consult the owner's manual for your product to determine whether your portable generator model has a bonded or floating neutral. To obtain a copy of the owner's manual see: Where can I download a user manual for my Generac portable generator?

 

Ultimately, local code will dictate whether generator grounding is required in your scenario: Does a Portable Generator Need to Be Grounded?

 

Environment

• This article applies to Generac portable generators. Always reference the owner's manual for your specific generator model for the most accurate information regarding the configuration of its neutral wire and grounding requirements.
  
• All Generac home standby generators incorporate a floating neutral. See here for information on the control wires for home standby generators: What is the layout of the control wires and what do they do?

What is the neutral wire?

A single electrical circuit consists of two wires. One carries the current from a source to a load, and the other returns this current back to the source. In any electrical circuit, this loop must be closed for the current to flow freely.

• The wire that carries an electrical current from a source to a load is called a “live/hot wire”
• The wire that returns the current back to the source is called a “neutral wire”, or simply neutral
• Contrary to these two, a “ground wire”, or just ground, is not a part of the electrical loop and only carries current in a fault condition, quite literally into the ground (which is why it is often also called earth). The ground wire is basically a protective wire, the purpose of which is to ensure the safety of the system.

A common example of how the live, neutral, and ground wires work together is a home's electrical outlet:

 

In this example, the "hot" or "live" wire carries the current from the source (the home's utility service) and the neutral returns the current back to the circuit from the cord connected to the outlet.

Bonded neutral generators

In a bonded neutral generator, the neutral is bonded to the generator’s frame. This means there is a physical connection between the generator's ground and neutral connections.

Most open frame generators, like the GP8000E below, incorporate a bonded neutral:

 

 

The location of the generator's ground varies by model, but it is typically grounded to the external frame with a wingnut or bolt:

 

 

See this resource for information on grounding a portable generator: Does a Portable Generator Need to Be Grounded?

Consult the owner's manual for your specific generator model for additional guidance and instructions on how to safely and properly connect the generator to a building electrical system.

 

Floating neutral generators

In a floating neutral generator, the neutral is not bonded to the generator’s frame. This means that there is no physical connection between the generator's ground and neutral connections.

Most inverter generators, like the GP3300i below, incorporate a floating neutral:

 

 

Most generators with a floating neutral feature an equipment ground, which connects the generator frame and the ground terminals on the AC output receptacles. This allows the generator to be used without grounding the frame of the generator.

 

With floating neutral generators, the stator winding is isolated from the frame and from the AC receptacle ground pin. Electrical devices that require a grounded receptacle pin connection will not function if the receptacle ground pin is not functional.

 

Why is my GFCI tester reading 'open ground'?

• When using a floating neutral generator, a GFCI tester will almost always show an open ground reading because there is no bonded connection between neutral and ground at the generator.
• GFCI testers check for continuity between the ground and neutral. Since a floating neutral generator does not have the neutral bonded to the frame/ground, the tester reads this as an "open ground" condition.
• This is normal for a floating neutral system when plugging into the generator directly. 

 

Additional considerations

• Ultimately, local code will dictate whether generator grounding is required in your scenario: Does a Portable Generator Need to Be Grounded?
• If plugging a generator into an RV or similar application, a neutral-ground bonding plug may be necessary to avoid abnormal readings and nuisance tripping.
• If experiencing frequent GFCI breaker tripping, see here: Why does the GFCI outlet keep tripping?
• If the GFCI breaker is tripping when used with a manual transfer switch, see here: Why Does the Generator GFCI Breaker Trip on Some Generators When Used With a Transfer Switch?