WiremanWireman · Neutral and ground bonded at a subpanel: troubleshooting for electricians · 2023 NEC ·
Neutral and ground bonded at a subpanel
Find out where the bond belongs, remove the extra one and keep neutrals and grounds separate.
Before you start
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How it works
The neutral and the ground are connected in exactly one place: the service disconnect, or the source or first disconnect of a separately derived system like a transformer. Downstream of that point they stay separate so neutral current returns only on the neutral. A bond at a subpanel puts part of the neutral current on the ground wires, conduit and anything they touch, and a loose feeder neutral can then put voltage on every metal enclosure.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- What feeds this panel?
- It’s the first disconnect after the meterThe bond belongs here
- Another panel, or a meter-main with its own mainTest: Look at the neutral bar and the enclosureExpect: Neutral bar on insulators with no screw or strap, and grounds on a separate bar fastened to the enclosure.
- Bonding screw or strap installedDoes the feeder bring a ground back to the source panel?
- Yes, there’s a ground or metal conduitBond installed in a subpanel
- No, only hots and neutralSubpanel with no feeder ground
- No screw, but grounds and neutrals share a barGrounds landed on the neutral bar
- No bond and the bars are separateTest: Check the neutral bar is isolatedExpect: OL (open). Some lighting or electronic loads left connected can show a high reading; anything near 0 Ω is a bond.
- OL or very highNeutral is properly isolated
- Low ohms or continuityA neutral touches ground somewhere downstream
- Bonding screw or strap installedDoes the feeder bring a ground back to the source panel?
- A transformer secondaryWhere is the transformer’s neutral (X0) bonded to ground?
- Only in this panel (first disconnect)Bond at the first disconnect of a transformer
- At the transformer and also in this panelBonded at both the transformer and the panel
- Not bonded anywhereTransformer secondary isn’t bonded
- It’s in a separate buildingWhat does the feeder from the main building include?
- Two hots, neutral and ground (or metal conduit)Test: Look at the neutral bar and the enclosureExpect: Neutral bar on insulators with no screw or strap, and grounds on a separate bar fastened to the enclosure.
- Bonding screw or strap installedDoes the feeder bring a ground back to the source panel?
- Yes, there’s a ground or metal conduitBond installed in a subpanel
- No, only hots and neutralSubpanel with no feeder ground
- No screw, but grounds and neutrals share a barGrounds landed on the neutral bar
- No bond and the bars are separateTest: Check the neutral bar is isolatedExpect: OL (open). Some lighting or electronic loads left connected can show a high reading; anything near 0 Ω is a bond.
- OL or very highNeutral is properly isolated
- Low ohms or continuityA neutral touches ground somewhere downstream
- Bonding screw or strap installedDoes the feeder bring a ground back to the source panel?
- Only two hots and neutralOlder 3-wire feeder to another building
- Two hots, neutral and ground (or metal conduit)Test: Look at the neutral bar and the enclosureExpect: Neutral bar on insulators with no screw or strap, and grounds on a separate bar fastened to the enclosure.