When it comes to generator safety, It’s shocking just how much there is to take into account. And the issue of grounding a generator might be one that you overlook or even disregard. However, knowing what happens if you don’t ground a generator might make you think twice.
If you don’t ground your generator, you risk damaging your electrical equipment as wiring or sensitive circuitry can be affected and might pose a risk of electrocution. Your electrical equipment can also overheat, thereby creating a risk of fire.
As you can see, not grounding a generator can be a costly mistake, so it’s something you shouldn’t ignore. That’s why, below, we’ll shed some light on the purpose of grounding and what can happen if you don’t ground your generator.
What Exactly Is Grounding?
When we talk about grounding a generator, we’re not talking about the ground wire mentioned above. It’s separate but related.
Grounding an electrical system such as a generator involves connecting its neutral conductor to the ground.
This connection is made via a low resistance ground wire connected to an electrode in the ground. Typically, the electrode is a metal rod driven deep into the earth.
Why Is Earthing Required for a Generator?
Earthing is the term used for grounding in the UK, EU, and other countries. So, why is it required for a generator?
A generator is an electrical system. So, it should meet the National Electrical Code (NEC)’s electrical safety requirements.
If you look at NEC 2020 Article 250.4(A)(1), it refers to the need for a connection between an electrical system and the earth. The purpose is to deal with voltage spikes and power surges. Also, it stabilizes the voltage through the system by dissipating excess voltage via the earth.
The low resistance connection to the ground electrode provides the path of least resistance for the excess energy to take to the earth.
Why the earth? Because the earth has an enormous capacity to dissipate electrical current.
Removing excess energy from the system to the ground renders it harmless. If it were to flow through the other wires in the system, it could damage equipment and overheat appliances, causing fires.
There’s an excellent explanation of this video of Grounding, System and Equipment by Mike Holt:
Risks of Not Grounding a Generator
If your generator isn’t grounded, there’s no protection from voltage spikes. Your system would be vulnerable to power surges arising from normal operation. For example, when appliances turn on and off.
These things could overload the wiring. Appliances connected to the generator during a voltage spike may suffer damage. Worse still, they might or overheat and cause a fire. The generator itself may overheat, and with an engine running it, that’s not good.
Damage to wiring insulation is one of the issues that can result from voltage spikes. Such damage can cause the type of fault mentioned above, where an exposed live wire touches an appliance’s metal casing.
Of course, as you’ve seen, you have the ground wire as a safety mechanism. However, the system’s neutral to ground connection should prevent the voltage events that cause such damage.
Do I Really Need to Ground My Portable Generator?
Well, all generators need to be grounded. So, the real question is whether you need to do anything to ground it.
When Don’t You Need a Ground Electrode?
Although grounding is necessary, you may not need a ground electrode to achieve that. Let’s explain.
The Occupational Safety and Health Administration (OSHA) provides guidelines for portable generators on construction sites. They apply where:
- You’re plugging your equipment into the generator’s receptacles.
- There’s low resistance bonding to the frame of:
- All the generator’s non-current carrying parts like the fuel tank, engine, and housing.
- The ground conductor terminals in the receptacles.
- It’s a neutral bonded generator, meaning that its neutral conductor connects to its frame.
If you meet these requirements, you won’t need to ground your portable generator with a ground electrode like a grounding rod.
Instead, the generator’s frame can act as the ground electrode. So, it’s grounded without you having to do anything.
When Do You Need a Ground Electrode?
Naturally, that’s the next question. So let’s look:
You Don’t Meet the Above Conditions
If the neutral conductor on your generator isn’t bonded to the generator’s frame, it’s a floating neutral generator.
They’re usually used as standby power for homes or other premises. In that mode, they connect to the grounded neutral conductor within the premise’s utility service.
If using this type of generator as a standalone, you won’t meet the third OSHA condition. So, you must ground the generator using a ground electrode connected to the frame. It’s not that hard to do, as you’ll see from this video:
You’re Powering a Structure via a Transfer Switch
This is where you use your portable generator to power your home using a transfer switch.
The transfer switch transfers power from your utility supply over to your generator. It ensures that the utility and generator don’t supply your house simultaneously because that could be dangerous.
In this situation, you’ll need to connect the generator to a ground electrode. However, how you do this is dependent on your generator.
Again, we come back to whether your portable generator has a floating neutral or a bonded neutral.
Floating Neutral Generator
As mentioned above, in a floating neutral generator, the neutral isn’t bonded to the frame. So, the generator’s neutral conductor isn’t grounded.
When you use it to power your home, your generator must connect to your utility’s grounded neutral conductor.
So, your transfer switch will only transfer the live conductors to your generator, not the neutral. In this way, your generator connects to your utility’s grounded neutral conductor.
That means you won’t need to attach the generator to its own ground electrode. Indeed, you mustn’t because having two neutrals grounded would be a breach of the NEC code.
Bonded Neutral Generator
If your generator’s neutral conductor is bonded to its frame, the transfer switch must transfer both live and neutral conductors.
You’ll also need to connect a ground electrode such as a ground rod to the frame in the same way that the utility supply is grounded via a ground electrode.
This video should help you understand these different switching and grounding arrangements:
What Is a Generator and What Does It Do?
Let’s start by understanding a bit about generators. A generator uses mechanical energy from an engine to move electrical charges in the generators’ wiring. The flow of these charges is the electricity that the generator outputs.
Like your home’s main power supply, it has hot and neutral conductors or wires. Along with the appliance you’re powering, these two wires form a circuit through which the electrical current flows.
In simplistic terms, the hot wire conducts the current to the appliance. The neutral wire returns the current back to its source. That is the generator.
There’s a third wire in the system, called the ground wire, but it’s not part of the electrical circuit. Under normal operating conditions, it doesn’t carry electricity. It’s a safety mechanism to deal with faults. For example, when a live wire touches a metal appliance casing, energizing it.
It gives the fault current a low resistance path back to the source instead of via the metal casing, so prevents electric shocks.
You should now have some understanding of when and how you need to ground a generator and what happens if you don’t. Essentially, it comes down to this:
|Generator Type||Standalone Use||Backup for Utility-Supplied Premises||Purpose|
|Bonded neutral||The frame can act as a ground, without ground electrode||Ground electrode required at the generator; live and neutral must be switched||Protect equipment from voltage spikes and surges. Prevent damage to components and wiring that might pose electrocution and fire risks|
|Floating neutral||Ground electrode required||No ground electrode required at the generator; only live must be switched|
However, this is a simplified summary of a complex topic. While it may be illuminating, it doesn’t equip you to deal with all grounding issues that might arise. Always consult a qualified contractor. This is one situation where being a bright spark isn’t a good thing.
- How to Ground a Portable Generator | The Complete Guide
- How to Run a Generator in the Rain (And Not Ruin It)
- Can You Plug a Generator Into a Wall Socket?
- Can You Connect a Power Strip to a Generator?
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