A Three-Wire Feeder, A Bonded Subpanel, and a Seller's Ground Rod
A 1978 two-story house has a 150-amp service panel and a 60-amp subpanel in the attached garage. The subpanel is fed by 6-gauge, 3-wire NM cable: two ungrounded conductors and a neutral, with no equipment grounding conductor. Inside the subpanel, the neutral bar is bonded to the enclosure with a green screw, and the branch-circuit grounding conductors land on the same bar as the neutrals. Two 20-amp breakers each have two conductors under a single lug. The subpanel is a 12-circuit panel with six spaces in use, mounted on plywood, with no main breaker in it; the feeder originates at a 60-amp breaker in the service panel, which is on the opposite side of the same building.
1. Evaluate the feeder and the bonding arrangement, and describe how you will present it to the buyer.
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Three findings that stack, each making the others worse.
- No equipment grounding conductor in the feeder. For a subpanel in the same building as the service, the feeder should carry a separate grounding conductor. Using the neutral as the grounding path is an obsolete arrangement.
- Neutral bonded to the enclosure at the subpanel. With that bond in place, neutral return current splits and travels on the panel enclosure and every metal path connected to it - conduit, water piping, appliance frames.
- Result: the enclosure sits at a potential above ground during normal operation, so a person touching the panel and a grounded appliance at the same time can complete the circuit. The bond also creates parallel return paths that can defeat overcurrent protection.
In the report: describe each condition, give the consequence in plain language ("the panel enclosure can become energized under normal use"), and recommend evaluation and correction by a licensed electrician. Don't price it and don't cite a code section you can't support from the edition the local authority enforces.
2. Two conductors share a single lug on two 20-amp breakers. Evaluate and write the report line.
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What is happening: breaker terminals are listed for one conductor. With two, one wire sits proud of the lug or under-torqued, resistance rises, the joint heats and arcs under load, and the breaker may never trip because the heat is at the terminal, not in the breaker's sensing element. This is a recognized fire cause and it is invisible once the cover is on.
Report line: "Two branch circuits are terminated under a single lug on each of two 20-amp breakers. The terminals are not designed for two conductors; the connection is a fire and overheating risk. A licensed electrician should separate these onto individual breakers."
Do more than write it: note which areas the two circuits serve (useful to the electrician), and check the remaining terminals, the main panel, and the neutral bar for the same condition. Where you find one double tap, look for others - it is a pattern, not an accident.
3. The seller proposes to "just drive a ground rod at the subpanel" instead of pulling a new feeder. Evaluate that proposal.
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It does not work, and it can make things worse.
A ground rod is a connection to earth, not a fault-current path back to the source. Earth has too much resistance to carry the current a 20-amp breaker needs to trip. If a hot conductor contacts the enclosure, the current still tries to return over the neutral-as-ground path, and the rod adds yet another parallel route through the soil and the building's other grounded metal.
The fix that actually addresses the hazard: a feeder that includes an equipment grounding conductor, with the neutral isolated from the enclosure at the subpanel and the enclosure bonded to the new grounding conductor - which may mean a new 4-wire feeder or an approved retrofit. A grounding electrode at a subpanel is only a supplementary connection and never substitutes for the equipment grounding conductor.
Report: the proposal was made, it does not correct the condition, and a licensed electrician should design the repair. Keep the exchange in your file; if the buyer waives the item, that record protects the report you wrote.