Removing the Neutral-Ground Bond in the Generator

This post is kind of advanced, but it is something that everyone who lives off grid and runs a generator needs to think about. I will make a disclaimer that if you are in doubt, hire an electrician to do the work for you.

For safety and NEC code reasons, a home’s AC neutral wire needs to be connected to the home’s ground system. This is known as the [B]Neutral-Ground Bond[/B].

The catch is that [B]the Neutral-Ground Bond can only occur in one place[/B]. If there are two Neutral-Ground Bonds, it is a safety hazard, as current can travel wires that it isn’t supposed to. (Note, an exception might be made at an outbuilding with it’s own sub-panel and ground rod, but let’s leave that out for now.)

In a regular home, the Neutral-Ground Bond is usually made in the home’s main AC power panel, where the outside cabling connects to the house.

In a totally off-grid solar powered home, the Neutral-Ground Bond can also be made in the main power panel. The problem occurs when a portable generator is connected to the home’s electrical system. Many portable generators have a Neutral-Ground Bond inside. This means that if a generator is connected to a home’s electrical system, there will be two Neutral-Ground Bonds in the system.

On my system, I wanted to have the single Neutral-Ground Bond inside the Midnite Solar epanel. This is where all the AC wiring is distributed from the inverter and generator, and to the AC power panel. But my generator has a Neutral-Ground Bond inside. So I disconnected the Neutral-Ground Bond in the generator, and made the bond in the epanel. It was a little tricky to do, and there was nothing in the generator manual about it.

How did I know there was a Neutral-Ground Bond in the generator? With the generator off and the generator circuit breakers ON, I removed any plugged in cables, then used an ohm meter to check across the ground pin and the neutral pin at the 240V receptacle. A zero or very low reading means they are connected inside somewhere, and they were.

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I looked over the generator to see if there was an easy way to remove the connection and didn’t find any. So I figured the connection was made in the voltage regulator (AVR).

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I removed the two screws on the AVR cover, took the cover off, and looked inside. I found where the neutral (white), ground (yellow), and L1 and L2 (black and brown) exited the AVR. I verified these wires with the ohm meter by checking across each terminal and the pins on the receptacle. I saw that the neutral wire had a short white jumper wire that joined the yellow ground wire where it was bonded to the metal chassis:

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I disconnected that white jumper wire from the ground terminal:

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I taped up the ring terminal with some red tape to keep it insulated. If I ever need to reconnect it for some reason, it will be very simple.

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I checked everything with the ohm meter, and the ground to neutral connection was gone. I put the AVR cover on and plugged in the cable.

Then I went inside the house and inside the epanel, I connected the ground bus bar to the neutral bus bar:

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Done!

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