Estimated reading time: 3 minutes
Electricians know they should separate grounds and neutrals in a subpanel. Some local code officials, not so much. But why is it so important?
This quick guide uses visuals to illustrate the dangers of improper bonding.
Understanding the Basics
A subpanel is like a mini electrical box that gets power from your main panel, and it’s important to keep the ground wire and neutral wire separate inside it. If these wires accidentally connect, electricity could flow where it shouldn’t, potentially shocking you or damaging your appliances. Think of it like keeping the “emergency escape route” separate from the “regular road” to prevent electrical accidents.
In a correctly wired electrical panel, the ground wire provides a safe path for electricity to flow back to the source in case of a fault, protecting you from shock.
The neutral wire carries the normal current flow back to the source. These two paths should be kept separate in a subpanel.
What Happens When Ground and Neutral Are Bonded?
Let’s look at what happens when we incorrectly bond the ground and neutral in a subpanel.
First, we set up a test panel with amp probes to measure the current flow on each wire. The current should be balanced in a properly wired panel, with the majority flowing through the hot and neutral wires.
The ground wire should show little to no current.
The image at right shows amp probes that reflect the balanced current flow in a correctly wired panel.
Watch the video below as we introduce a bonding screw between the neutral and ground bars in the subpanel.
See how the current on the neutral is cut in half, and the other half is now flowing through the ground wire?
This situation is dangerous because the ground wire is now energized and could cause an electrical shock.
Even without a bonding screw, a simple mistake like connecting an equipment ground to the neutral bar can have the same effect. As you can see, even one misplaced wire can create a serious safety hazard (keep watching the video).
Key Takeaway
Always ensure grounds and neutrals are separated in your subpanels. This simple step can prevent dangerous electrical shocks and keep your electrical system running safely.
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