Quick answer
The short answer
In a sub-panel, the neutral and ground wires must be separated—they should never be bonded together. Only the main service panel bonds them. A bonded sub-panel sends current on the ground wire, which can energize metal cases of appliances and metal piping. The fix is removing the bonding screw or strap, separating the neutral and ground bus bars, and verifying continuity.
What to know first
- Main panel: neutral and ground bonded together (correct).
- Sub-panel: neutral and ground separated (correct).
- A bonded sub-panel is one of the most common older-home defects—and one of the most dangerous.
Why this matters
In a properly wired electrical system, ground wires don’t carry current under normal conditions—they only carry current during a fault. If a sub-panel has its neutral and ground bonded, then normal return current (which is supposed to flow on the neutral) can also flow on the ground wire. That energizes everything connected to ground: appliance cases, water pipes, ductwork, metal conduit.
Most of the time you don’t notice. Until something goes wrong—a slight tingle on a metal appliance, a corroded connection that becomes a shock hazard, or a bond that fails and causes nuisance trips on GFCIs.
How we find it
We open the sub-panel and look. The neutral bus bar should not be touching the metal panel enclosure—either through a bonding screw, a bonding strap, or both bus bars on the same isolated bus.
If it’s bonded, the fix is straightforward: remove the bonding screw or strap, separate the neutral and ground bus bars (most panels have provisions for both), and re-land the wires on the correct buses.
When sub-panels need their own ground rod
Detached structures (shop, ADU, detached garage) often need their own grounding electrode system at the sub-panel, plus a 4-wire feeder from the main building. That gets the bonding right at the new structure without bonding the sub-panel itself.
For attached sub-panels (interior or attached garage), no separate ground rod is needed—the 4-wire feeder ties the sub-panel ground back to the main panel’s grounding system.
Main panel vs sub-panel bonding
They look similar but the bonding rules are opposite.
| Feature | Main panel | Sub-panel |
|---|---|---|
| Neutral & ground | Bonded together | Separated |
| Bonding screw | Installed | Removed |
| Ground rod | Connected here | Not directly (uses 4-wire feeder) |
| Feeder wires | 3 wires from utility | 4 wires (2 hot + neutral + ground) |
Related next steps
If this sounds like what you are dealing with, these service pages explain the next step.
Frequently asked questions
How do I know if my sub-panel is bonded?
We have to open it. The bonding screw or strap will be visible if installed. We don’t recommend opening sub-panels yourself.
Will a bonded sub-panel trip my breakers?
Sometimes—it can cause GFCIs downstream to trip nuisance, since the ground is carrying current. But often there’s no visible symptom until something fails.
Is correcting a bonded sub-panel a big job?
Usually no—removing the bond and re-landing wires takes 30–60 minutes per panel. The hard part is identifying it in the first place.
Do detached buildings still need a separate ground rod?
Yes—any separate building with a sub-panel needs its own grounding electrode system. We install during the sub-panel install or as a retrofit.
Work with our team
Call (661) 293-0213 or use the contact form.
