Grounding a Generator

Since an average American electricity consumer loses power at least once per year, many households have backup generators. But to be used safely, grounding any generator is necessary.

If you don’t know whether your generator needs grounding or how to do it, you should follow the rest of this guide to make sure you’re staying safe. We’ll even explain a little bit about grounding in general, so you understand the basics. Further, we will focus more on the grounding requirements of a portable generator in our article.

What Are Grounding and Bonding?

You may define the grounding of an electrical system as connecting any electrical circuit or equipment to a reference ground.

Bonding is defined as the intentional connection between the grounded circuit conductor (neutral) and the grounding means in the portable generator such as the grounding bolt.

Grounding and bonding are a means to prevent the risk of shocks and electrocutions.

Generators are no exception to the grounding rule. Many are permanently grounded using a metal rod hammered into the ground and a wire connecting all of the conductive elements of the system to the Earth. 

Why is Grounding Necessary?

The frame of any portable generator is fabricated from metal and may become live in case of a ground fault. If any person comes in contact with the ungrounded metal frame, he may suffer mild or severe electrical shock, depending on various conditions and factors at the place of installation. In worst cases, this may even lead to electrocution.

Grounding the frame diverts the fault current to the ground and brings the generator’s frame to the ground potential, eliminating any risk of an electrical shock.

If you don’t ground your generator, you may end up damaging your equipment or sensitive circuitry, mild or severe electrical shocks, and even electrocution. If the fault current passes through the engine or the fuel tank, the fuel may catch fire posing a fire safety hazard.

You need to ground your portable generator properly to minimize or eliminate these risks by diverting the fault or stray electrical current to the ground.

Do I Need to Ground My Generator?

You don’t need to ground most portable generators in modern times while some of the older generators may still need to be grounded.

You are always better off following the manufacturer’s instructions if you do or do not require grounding before use.

In order to understand the grounding requirements completely, you may have to understand

  1. The recommendations of the Occupational Safety & Health Administration (OSHA),
  2. The classification of the systems by the National Electrical Code based on the way the transfer switch handles the ground conductor.
  3. Whether your generator has a neutral bonded frame or not.

Don’t be overwhelmed if you cannot completely get it now. We will present all salient features of both OSHA, NEC, and neutral bonding in simple and clear terms below.

OSHA & NEC’s Recommendations To Ground A Portable Generator

Most owner’s manuals recommend that you ground your portable generator using a copper ground rod driven several feet into the ground. OSHA bases its recommendations on whether the system has a permanent connection to the grid or not. The systems are divided into two categories based on this condition.

Separately derived system (SDS)

Separately derived systems are completely isolated from the grid. The following are considered the separate systems

  1. If all power connections from the generator are only through the plug and chord arrangement from the power outlets mounted on them without the use of any transfer switches.
  2. If the generator’s transfer switch makes or breaks the neutral ground connection also. All three-phase, 4-wire, and single-phase, 3-wire systems fall in this category.

Non-Separately Derived system (NSDS)

Most home applications fall in this category as the transfer switches do not open or close the ground connection and the system ground is permanently connected to the grid ground.

Ommission of Grounding Rods

As per OSHA, a generator frame need not be grounded with a copper rod and can act as the ground itself if it is separately derived and meets the following requirements:

  1. if the generator only feeds power to electrical equipment mounted on it or connected to it by extension cords and plugs through power receptacles mounted on it.
  2. All the metal parts that are not designed to carry any current, such as internal combustion engines, the fuel tank, and the generator housing are bonded to the metal frame.
  3. Equipment grounding conductor terminals, forming part of the power receptacles mounted on the generator are also bonded to the frame.

If all of the above conditions are met, the frame of the generator acts as the ground bar and eliminates the need for any separate copper rod.

In case the above conditions are not met, then a separate grounding rod is a must. One such major condition is when the portable generator feeds power to the home, office, trailer, shop, etc through a transfer switch.

How to ground the neutral of your portable generator connected via a transfer switch is governed by NEC article 250.

You will be curious to know the conditions when the transfer switches would transfer the neutral to the generator and otherwise. It depends on the bonding of the neutral conductor to the frame, as you will see in some detail below.

Bonded Neutral Generator

The neutral circuit is bonded to the frame in most modern generators, particularly stand-by and open frame ones. According to Article 250, for such portable generators,

  1. The transfer switches must transfer the neutral to the generator.
  2. Neutral must be grounded at the nearest possible point, known as the first means of disconnect, and should not be grounded more than once. This helps in reducing voltage spikes and reduces vulnerability to power surges.

Consider the electrical circuit of your home fed from a utility source. The incoming cables from the source are connected to the breaker box (distribution board) that further distributes power within your home. All the neutral points get grounded to a single common point in this metal box.

As the generator is already having a neutral ground conductor, the transfer switch must transfer the neutral also to the generator in addition to the live wires during a power outage because you cannot ground the neutral twice. Such portable generators act as standalone units.

Floating Neutral Generator

Not all portable generators have a grounded neutral and are known as floating neutral generators. Such a generator depends on the ground provided by the home distribution box. For them, you must not transfer the neutral through the transfer switch. The grounded neutral of the home panel is extended and gets connected to the floating generator neutral.

The appliances connected to such portable generators get the neutral from the generator that is grounded via the home distribution board.

Most inverter portable generators have their neutral floating.

How to ground your portable generator?

So by now, you have concluded that you need to ground your portable generator with a separate grounding rod to an external ground. It is always better to deploy a qualified electrician to ground your generator. However, if you still want to carry out the job yourself, read through to know the required details.

Grounding Rods & Copper Wire

A grounding rod is a piece of conductive material designed for hammering into the ground. They’re usually made of copper, and they often have a protective coating to prevent the copper core from being damaged during installation and after it’s exposed to the elements. 

It’s important to start with a long copper grounding rod because it needs to be driven to a depth of at least four feet. That means that if it’s at an angle, it needs to travel further to reach the right depth. You should always check your local electrical and building codes before you ground an appliance. There are rules you should know to make sure your work is in compliance. 

Your copper grounding wire should also be in compliance with the relevant electrical code. The more power your generator is capable of producing, the heavier the gauge of ground wire required to ground it. Using a 6-gauge copper wire is probably best for a home standby generator. 

Even though it’s more expensive, there is no harm in using a heavier gauge than you need. The risk of using too small of a wire outweighs the extra cost. 

5 Steps to Ground a Portable Generator 

Follow these five steps to carry out the grounding work yourself.

1. Gather Your Tools and Materials

Grounding any generator is easy, but you need the right tools and gear and of course the two main components: Properly-sized copper grounding wire and a copper grounding rod that’s both at least ⅝-inch diameter and eight-feet long. You’ll also need some tools:

  • Screwdrivers
  • Wrenches 
  • Pliers
  • Sledge Hammer
  • Block
  • Wire Strippers

2. Install Your Grounding Rod

If you have some aggression to work out, now’s a good time to do it. You’re going to use your sledgehammer and block to drive your copper ground rod at least eight feet into the ground. The block will help protect the rod from your hammer impacts. 

If you encounter hard ground, you can wet it down a bit to loosen the soil, and you can drive the rod at a bit of an angle to make it easier in rocky terrain. 

Since the rod is quite tall, you’ll have to find a way to get leverage over it to hammer it down. You can use a sturdy stepladder, or you can dig a small hole, and set the rod in it to make it shorter before you start hammering. You can also use a hammer drill if you have one. There are also other specialty tools you might be able to purchase or rent if you have a hard time. 

Just make sure you follow the electrical code. By complying with its rules, you’ll get the rod deep enough that there isn’t a risk to anyone standing nearby. 

3. Install the Rod’s Grounding Lug 

Once the ground rod is far enough into the soil, you can stop hammering. There will be a bit of the ground rod above the ground level. Make sure to comply with the electrical code about how much of the copper ground rod may be above the surface. 

Now you can attach a piece of hardware called a grounding lug. It’s a fastener that allows you to connect copper wire tightly to the grounding rod. Use your pliers or wrenches to tighten the lug to the rod. Then, use your wire stripper to remove a few inches of insulation from your copper wire.

4. Fasten Your Grounding Wire to Rod’s Lug

You can wrap it through the grounding lug you attached to the rod. Tighten the lug around the copper grounding wire, tightly securing it to the rod. 

5. Connect the Wire to the Generator

Finally, you can connect your wire to the lug on the generator. Look for the grounding bolt on your generator. You can loosen it with pliers or a wrench. Sometimes you can use a screwdriver. Stop unscrewing the grounding bolt once you have enough of the bolt’s post exposed. 

Grab your copper wire coming from the lug on the copper rod and cut it with about three extra inches of length. You can bury most of it so you won’t trip over it. Now, use your wire strippers to strip a bit of the insulation off the end of the wire. Wrap the exposed copper around the bonding lug. Use your pliers to twist the copper wire into a loop around the lug’s post, and then twist it back on itself. 

To completely secure the connection, tighten the lug down so there is no chance the wire can slip off the bolt. Now you can clean up and put all your tools away. The job is done!

Special Circumstances for Grounding a Generator

If you have an RV or other vehicle with a shoreline charging system, you can run power to a special plug on your vehicle to keep its components charged when the vehicle’s engine isn’t running.

For instance, if you park your RV at a campsite, you don’t want to idle the engine all night to turn on the lights in the cabin. Instead, you’ll want to plug into a power source. For many, that source is one of the small generators available in the market. 

Some generators are designed to work with RVs, and they may even have a place where the RV’s grounding connection can fasten to the generator. This effectively grounds the RV to the generator. You should always follow the instructions in the owner’s manual for your RV to make sure you ground the vehicle properly when you’re plugged into a power source. 

Grounding a Generator Bottom Line

Have you enjoyed our list of steps for grounding a generator? It’s not the most fun project in the world, but if you stick with our five steps for grounding, your generator will be safe to use. 

If you have questions or concerns, please drop us a line in the comment section. And if the information here was valuable to you, share it with your friends and family. We want to help as many people as possible!

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