Neutral And Ground On Same Bar In The Subpanel? (Fix It Now!)
The electrical components of your home or business can require professional intervention much of the time for good reason. Not only is it a complicated setup, especially to DIYers, but it is dangerous as well. Plus there is the potential of installation going wrong on top of all that.
When it comes to your subpanel, you will have to deal with neutrals and grounds. When can they be used on the same bar? The answer is that you should never have your grounds and neutrals on the same subpanel bar. They should only be connected at the last point of disconnect, which is at the main panel. Safety standards have changed, making it a code violation to have them on the same subpanel bar.
What is a Subpanel?
To better understand the entire setup, we need to know what a subpanel is. And to know what a subpanel is, we have to know what a main panel is. The main panel is known as the last point of disconnect before the service entrance.
Main panels generally have a single large breaker capable of shutting off power to the entire building. Visually speaking, you can tell a main panel apart from the shutoff breaker at the top of the box
A subpanel will look very similar in a lot of ways. The wires that run into the subpanel come from the main panel. You can have multiple subpanels depending on the size of the structure, but most residences will only have a single subpanel.
Subpanel Codes Pre-2008
Up until 2008, there were two ways to wire a subpanel according to the National Electric Code. The first was through a four-wire feed. In this method, there would be a pair of hot wires, a neutral wire, and a ground wire. Both the ground and neutral were isolated so that there would be a separate path to the panel.
The second way was through a three-wire feed. That would be two hots and a neutral. The ground wire, meanwhile, would be connected to the neutral together at the subpanel. For this method, that meant no other recourse but to have the neutral and ground wires connected together.
The latter had several rules attached to it, however. The three-wire method only worked for detached builds and only if that building had its own specific grounding electrode system. Moreover, you could not have a continuous metallic path that would be bonded to that grounding system in the corresponding building.
Starting with 2008, however, the National Electric Code changed. The four-wire feed became the only acceptable means for wiring a subpanel. Remember, the four-wire method involves a pair of hot wires, a ground, and a neutral.
This means that the neutral and grounds have to be isolated from one another. That is why it is not okay to have the neutral and ground wires on the same bar in your subpanel. It all comes down to when it was installed and a number of other factors related to the panel.
What is the Purpose of the Running the Ground and Neutral Wires into the Earth?
Typically speaking, the ground and neutral wires are connected from your main panel to your subpanel through the earth using rebar, rods, pipes, or wires. The idea with running them into the earth is that you want to add a layer of protection against static charges or lightning surges that would otherwise impact your electrical system.
The second function of running those wires into the ground is to provide an emergency path where they connect to the main panel. Basically, if there is a short somewhere between the metal component that is grounded and the energized conductors, then there is a path back to the panel to trip the breaker that is associated with that specific circuit.
Circuit breakers trip on amperage curves and heat curves. A short circuit is one of the times where that amperage rating will trip the breaker. Think of it as an additional safety measure.
What Does the Ground Wire Do?
Also known as equipment-grounding wire, the ground wire provides a path from the metal parts of an electrical device. Those electrical devices could energize and post a shock hazard to the panel, doing damage in the process.
The ground wire carries that current when there is a ground fault. This happens when the hot wire (or a neutral wire that carries the current when the load is on) touches to the metal part of that device. It is usually due to a loose wire or some other type of deficiency.
The grounding wire provides a safe path for that electricity to go back to the panel to trip the breaker. When it gets back to the breaker, it trips that breaker, effectively killing the power. It is a safety mechanism meant to protect the panel and you.
When Should Neutrals and Grounds be Connected in a Subpanel?
For new builds or installations, the answer is never. The National Electric Code, as mentioned above, has changed the standards on how to wire a subpanel. They would only be connected to the same bar at the main panel.
Why Can’t You Connect Neutrals and Grounds on the Same Bus Bar in the Subpanel?
There is one primary reason that the three-wire method is no longer accepted by the National Electric Code. The reason being that you want a single path for power to return back to the source. The four-wire feed does just that.
If you were to connect the neutrals and grounds at the same subpanel, then the grounds would be able to take some of that power load and take it right back to the main panel. That is a very, very bad thing and something to be avoided.
The grounds should not have any power at all unless there is a surge of power. The grounds work to alleviate that surge by pushing the power’s path back into the Earth. Not only that but dividing up the power of the neutral means that the breakers connected to the neutral might not be able to effectively trip.
You may hear grounds referred to as “bare grounds”. The reason being that grounding wires are sometimes run through exposed wires or metal conduits. All of that means that they are easier to access than neutral wires. Neutral wires are always protected.
For the most part, this is rarely an issue as the grounds never have power running to them unless there is a surge. But when the grounds and neutrals are connected together in the same subpanel, any of the grounds down that path are capable of holding power.
Find out if you need a permit to add a subpanel.
Identifying a Subpanel Where Grounds and Neutrals are Connected
How do you visually identify a subpanel where the neutrals and grounds have been connected to the same bar? You would look for the white wires which are the neutrals. Those would be on the right bar while the grounds, which are bare copper wires, would be connected to the left.
At the top of the panel, you would see the two bars joined by a single bar, which is the subpanel neutral. There will also be a green screw to ground the panel as well. This is a bad thing because it creates a parallel circuit back to the main panel, which we definitely do not want.
What if You Have the Neutrals and Grounds Joined at the Subpanel?
Let’s say that you bought an older house that has the neutrals and grounds joined at the same bar in the subpanel. You are dealing with a current of 120 volts that is now capable of traveling in multiple paths. That would mean traveling on the metal conduit, then the neutral wire, and the ground wire as well.
When the two are joined at the same subpanel bar, then they have multiple paths to travel. That could mean the neutral current running into the bare conduit, which is bad news. Not only that, but the breaker for the main panel may not be able to trip, stopping that surge of electricity.
Take a look at how many subpanels you can have on a 200 amp service.
Here are some of the most relevant questions that other users had related to their electrical system, specifically crossing wires.What Happens if You Cross Hot and Neutral Wires?
The hot wires run into the earth, taking with it any electrical charge that has gone astray. If you touch that hot wire and you’re touching the earth (which is always), then you essentially become part of the circuit and get a shock.
Any time there is an electrical current that can shock you, it presents a serious danger. There is no way of knowing how strong the shock will be. It could range from a minor inconvenience to something far more serious or potentially deadly. You can experience a shock through an electrical appliance or light fixture, for instance.
The good news is that most electricians should be able to come out and remedy the issue. They will check to ensure that the wires are properly run into both the subpanel and main panel, correcting any issues with the prior wiring.
Ryan Womeldorf has more than a decade of experience writing. He loves to blog about construction, plumbing, and other home topics. Ryan also loves hockey and a lifelong Buffalo sports fan.
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