Adding a ground to an old two-prong outlet
When an older circuit has no ground wire, the ground added for a replacement three-prong receptacle, a replacement switch with a ground terminal, or a circuit extension must connect to one of six points the code lists.
What the code requires
This rule applies only to existing wiring with no equipment grounding conductor. It covers replacing an ungrounded two-prong receptacle with a grounding-type one, replacing a snap switch that has no grounding terminal with one that does, and extending an existing branch circuit.
The new ground may connect to any accessible point on the grounding electrode system, any accessible point on the grounding electrode conductor, the equipment grounding bar in the panel where the circuit starts, or the equipment ground of another branch circuit that starts in that same panel. It may also connect to the service neutral inside the service enclosure on a grounded system, or to the grounding bar in the service enclosure on an ungrounded system.
The code also points to a GFCI alternative for replacing ungrounded receptacles in 406.4(D), and to 404.9(B) for switches. This is work for a licensed electrician, and your building department can tell you whether a permit is needed.
On the job
- Tying a retrofit ground to an interior water pipe that is not part of the grounding electrode system, or to a circuit from a different panel, does not meet the code. Neither is on the permitted list.
- A three-prong receptacle installed with no ground and no GFCI protection is a common correction.
What changed in 2023
The 2023 edition added replacement snap switches to this rule and a new informational note pointing to 404.9(B).
Related sections
- NEC 250.50: Bonding all grounding electrodes together
- NEC 404.9(B): Grounding switches and metal cover plates
- NEC 406.4(D): Replacing receptacles: GFCI, AFCI and TR rules
Where this comes from
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Text is fastest. If you smell something burning or see smoke, call 911 first and keep away from the panel.
Kyle Robert Anderson KBC Electric · CSLB #1073066 · C-10 Electrical · Licensed since 2021