Does a Subpanel Need a Ground Rod? (Here’s Why)

Not so long since subpanel became a must in our lives. Nowadays, they are the reasons we can use our electrical devices and appliances amid lightning weather.

Such unseen exertion gets their blessing and boosts by the subpanel. It does the trick, but what about the ground rod that consumes unexpected electric shocks? 

You might be pondering does a subpanel need a ground rod? It does.

Yes, you heard right. The dangerous electricity gets eaten up and wrecked by the ground rod. Not saying the rod does most of the trick, but a subpanel without a rod will be like a car without a hood, not helpful when needed.

You get the article’s complete discussion regarding the relation between subpanel and ground rods. Your perception and knowledge about the ground rod are about to get enriched.  

Subpanel Need a Ground Rod

Is It Necessary to Put a Ground Rod for a Subpanel?

Yes. One ground rod or, in some cases, two ground rods are required for a subpanel.

Know what a subpanel is first. It’s an electrical panel wired downstream from the service equipment, known as the main panel. And ground rods dissipate static electricity and external high voltages of the lightning strikes.

The ground rod plays a crucial role in the safety and protection of your home appliances or electrical system. That’s why it is a must to have a good ground rod.

Otherwise, you might be digging into a good place to get electrical errors. Ground rod provides you safety from being shocked by open electrical outlets. No matter the structure, grounding is a must for any new construction or building.

Difference Between the Main Panel and Sub-panel

Many of you might make a similar gesture on both panels, but they are not. Might look familiar in terms of names and spoken characteristics, but there remains a vast difference in their roles.

The central panel is a section where the power enters from the electric company and distributes the power to all the sub panels and appliances of that house or business area. It controls all the electrical equipment by connecting and disconnecting them from the supply line.

On the other hand, the sub-panel acts as an intermediary between the electrical equipment in your house or premises and the main panel.

Though the sub-panel cannot produce more power independently, it can control every circuit so that the power supply will be more efficient.

Another thing to point out is that if there is a problem in any circuits, the sub-panel can help you to identify the faulty circuit. The central panel can work without the help of the sub-panel, but the sub-panel can’t.

Such slight differences can pay you big at times. There are no chances of seeing one lower and the other upper in terms of their usage, as yours. [1]

So, When Subpanel Need a Ground Rod?

A ground rod is a thick copper wire connected to the main panel. They are connected with the neutral transformers of your surroundings. You’ll see them buried under the ground near your houses or properties.

Every sub-panel outside the main building requires its ground rod. But sub-panel in the same building doesn’t require an individual ground rod.

These sub-panels are connected to the ground wire. The primary role of the ground rod is visible when lightning strikes. When lightning strikes, it will flow along the wires to get back to the ground rods of your main panel. And that’s where your ground rod does its service.

How to Install Ground Rod for Sub-panel

How to Install Ground Rod for Sub-panel

We have already known what the ground rod and sub-panel are. Now we have to connect them. To do this, you need to follow some steps.

Step 1: Select a suitable place to insert the ground rod

  • You need to select a place at least 2 feet far from the building
  • You need to avoid where the water pipeline, gas pipeline, or heavy rock area is inside the ground

Step 2: Select a ground rod

You have to select a high-quality ground rod to insert into the ground. As it stays a long time inside the ground, a high-quality and durable ground rod is required.

Step 3: Insert the ground rod into the ground

You must dig at least 8 or 2.4 meters into inserting the ground rod.

Step 4: Connect the rod with the sub-panel

  • Clamp one end of a ground electrode with the upper end of the grounding rod.
  • And another electrode end is connected with the sub-panel where all the grounds and neutral wire are attached.

This is how you can install a ground rod for your sub-panel.

Warning ⚠️

While you are busy installing the ground rod, don’t miss out on the precautions and safety measures. It is a must to wear safety gloves to remain aloof from shocks.

Also, certain boots are available that keeps you confined to the earth. Amid all these, don’t forget to disconnect all electronic connections associated with the rod. There are certain chances that can introduce short-circuits.

And always recommend you to do the insertion by an expert.

Why Do You Separate the Ground and Neutral in a Sub-panel?

You have to separate the neutral and ground terminals in a sub-panel. Because they are not the same thing, mixing them can be dangerous and suicidal to the machinery and the people.

Electricity takes any path back to the source. If the load is perfectly balanced in the circuit, there will be zero voltage. Zero voltage produces zero current.

There will be a smooth flow of current through any conducting material if the neutral wires are bonded together the imbalanced ground rod.. For example, ground wire, piping, etc. And back to the main panel.

So, if you want to keep your appliances and home safe and secure, you need to separate the ground and neutral in a sub-panel.

Purpose of Ground Rod

The only purpose of a ground rod is to form a ground field and produce an electrical path to dissipate the static discharge voltage to the earth. And we considered the electrical earth ground rod voltage is zero.

Mainly we measure voltages of other circuits taking the earth voltage zero as a reference.

Another main reason to use a ground rod is dissipating external high voltages like lightning strikes. It controls the murderous electric flow and buries them on the ground. These rods are the reasons your electrical appliances remain safe during lightning. They deserve some thanks for it, though.

One misconception is that a ground rod is used when a ground fault occurs. It’s never true. Only the ground wire is used for ground faults, not the rod.

The role of the ground rod in our daily life is immense. You get to experience it once there is heavy lightning in your area.

Sometimes, you also see the results of not having one surrounding your locals. If you don’t use one, your condition might be the same as theirs, which is disastrous.

How to Ground a Subpanel in a Detached Building?

In the case of a detached building, grounding a subpanel might require you to consult an electrician.

Any time you are using a single branch circuit or single multiwire branch circuit, you are required to establish a grounding system. So how do you establish a grounding electrode system or a grounding rod for a second building?

Let’s find out!

  • You have to install a feeder cable that contains an equipment grounding wire sized as required by IRC Section E3908
  • You need to install a grounding electrode in both buildings
  • Then you have to connect the feeder cable equipment grounding wire to the grounding rod wire at the second building’s subpanel grounding bus
  • Then connect the subpanel case to the grounding bus
  • Connect the feeder cable neutral wire to an isolated grounded bus at the second building subpanel. You must not connect the grounded bus to the subpanel case or the grounding bus.

You can get some idea over here:

Does a Subpanel in the Same Building Need a Ground Rod?

Yes! All the sub-panels of the main building must have at least one grounding electrode conductor. 

In the case of the same property, grounding a subpanel is easy as falling off a log. You’ll need to recheck and maintain a few conditions for sub-panel ground in the same building. Let’s have a look at those conditions.

Condition 1:

At first, while installing a second subpanel, you need to separate the neutral terminals. Because the neutral terminals are connected to the subpanel enclosure through spacers, not in a subpanel, to avoid grounding. The feed of the primary circuit to the sub-panel requires four cable wires, each individually insulated.

Condition 2:

A terminal slot is accepted for only one conductor in the grounding bus. Otherwise, there would have been mentioned. The terminal size is not an issue here, as it needs to fit only one conductor. As there are exceptions, make sure to follow the manufacturer’s instructions.

Condition 3:

Make sure never to connect the neutral terminals or bars to the subpanel’s ground or even close to it because it might result in electrical shock. Keep away metal ground rods from any part of the sub-panel.

Condition 4:

You can connect all the ground and neutral wires to the main panel, not the subpanel. Primary ground sources like ground rods can be bonded there too.

How Do I Know if My Subpanel Is Grounded?

When the ground rod is inserted into the ground and connected with the sub panel, the ground rod will give resistance and an impedance value in the multimeter.

You can confirm ensure by measuring the resistance and impedance of the ground rod that there is a ground rod and it is working correctly.

If the ground rod is working correctly, the multimeter will give you a value of voltage and current. The National Electrical Code (NEC) section 250-56 sets a requirement for a single ground rod or plate to have an earth resistance of 25 ohms or less. [2]

But if the ground rod isn’t working correctly, the multimeter will show you zero on the multimeter’s display.

This is how you can ensure that your ground rod is or isn’t working.

How Do Ground Rods Protect Your Electric Equipment and Appliances?

A grounding rod or two helps to divert higher voltage surges into the ground. It is essential for setting up your home appliances such as TVs, computers, receptacles, etc. 

Every home contains several electrical outlets or switches. If they are not grounded, rise to a surge might cause deadly results, especially if the electricity gets to flow through a human body to the ground.

Ground rods are usually made of copper or copper-coated steel. They are excellent conductors of electricity. They allow all the dangerous electricity to flow to the ground, ensuring the safety of you and your electrical panel.

Proper grounding gives your home’s electrical system stability. It also reduces the impact of electrical surges.


Q: Can You Wire a Subpanel with Three Wires?

Until the 2008 version of the National Electrical Code, there were two systems of wiring a subpanel: Four wires and three wires system.

In the three wires feed, two hot and one neutral wire are used; here, grounds and neutrals are connected at the subpanel. This feed only allowed the detached buildings to have their grounding electrode system. But after 2008, only four-wire feeds were acceptable. It keeps the grounds and neutral isolated to make feasible separate flow of current.

Q: Why are Two Ground Rods Required?

Electricity tends to return to its source; it doesn’t just get to the earth. So, if one ground rod is used, the electricity will return as usual. 

So, using another ground rod with the transformer makes a path for the flow to return to its source without hampering any wiring connection.

Q: What Size Wire Do I Need for a 100amp Sub-panel?

With the 80% NEC (National Electric Rule), the best size for a 100amp sub-panel is 1 AWG (American wire gauge). 1 AWG has 130amp ampacity but can conduct at most 104 amps.

Most houses use copper wire for electrical components, but you should use aluminum wires for more extensive infrastructure.

Q: Does a Subpanel Need a Separate Ground Rod?

Yes, a subpanel needs a separate ground rod as it defends your home against electrical surges of lightning strikes and short circuits. 

You must install a minimum of one ground rod for a subpanel in a detached structure. And if the main panel and sub-panel are in the same building, then a ground wire is enough.

Final Thoughts

At this point, you must be clear about the necessity of a ground rod in a subpanel. Don’t forget to double-check the requirements and resources that I have discussed in “Subpanel Need a Ground Rod” while installing a subpanel.

It’s always best to abide by the rules of NEC while installing electrical circuits. Still, I recommend keeping in touch with an expert in this field for your safety.

Related Content:

Ezekiel Mutitu

Ezekiel Mutitu is a man of many talents. He has an unquenchable thirst for knowledge, which has led him to do thousands of DIY projects. He loves learning about anything and everything - especially electronics and electrical items. Ezekiel knows that by being passionate about writing, he can help people from all walks of life understand complex topics and processes.

Recent Posts