Quick answer
An equipment grounding conductor (EGC) is the bare, green or green-and-yellow wire, or approved metal raceway or cable armor, that connects the metal parts of outlets, boxes and appliances back to the panel, giving fault current a low-impedance path so the breaker trips.
It carries no current in normal use. It only works when something goes wrong, such as a hot wire touching a metal case, and it is sized by the breaker that protects the circuit.
Quick facts
The key facts about Equipment Grounding Conductor, with sources:
- Common name
- The ground wire
- Allowed types
- NEC 250.118 lists 14 types, all metallic, including wire and some raceways such as EMT 45
- Sizing table
- NEC Table 250.122, by the rating of the overcurrent device 2
- Terminal on devices
- The green screw 9
Key takeaways
- The EGC is the ground wire in a cable, or an approved metal raceway, running back to the panel.
- It carries current only during a fault, and that current trips the breaker.
- It is bare, green or green with yellow stripes; never use it as a neutral.
- It is sized from NEC Table 250.122 by the breaker rating, not the load.
- Three-slot outlets without an EGC behind them give false comfort.
What the equipment grounding conductor is
Open a modern cable and you will find a black wire, a white wire and a bare copper wire. The bare wire is the equipment grounding conductor, or EGC, which electricians often just call the ground.
The EGC connects every metal box, the green screw on every receptacle and the frame of every grounded appliance back to the ground bar in the panel 9. At the service, the main bonding jumper links that ground bar to the neutral.
It does not have to be a wire, since NEC 250.118 lists 14 types, all metallic 5. IAEI gives electrical metallic tubing (EMT) as one raceway that can serve as an EGC under 250.118(4) 4.
How the EGC trips the breaker
Normally, current flows out on the hot wire and back on the neutral, and the EGC carries nothing.
If a hot wire touches a metal case, current takes the EGC back to the panel, crosses the main bonding jumper and returns to the utility.
Because the EGC has low impedance, the fault current is large and the breaker trips fast.
IAEI describes the EGC as the effective ground-fault current path that “facilitates the operation of the overcurrent protective device” 4.
OSHA puts it from the user’s side: if a tool’s metal frame becomes energized, the equipment ground provides another path for the current, rather than through the person 8.
Normal
- Current out on the hot wire
- Current back on the neutral
- EGC carries no current
- Breaker stays on
Ground fault
- Hot wire touches a metal case
- Current returns on the EGC
- Large fault current flows
- Breaker trips quickly
Why low impedance matters
A breaker trips fast only when current is far above its rating, and the fault current depends on how easily it can flow back, which is the impedance of the path. A solid, tight EGC lets hundreds of amps flow for a moment, and the breaker opens almost at once.
A weak path changes that, which is why IAEI says an effective fault path must be electrically continuous, have enough capacity and have low impedance 4.
A loose screw on a metal box, a corroded splice or a conduit joint that has worked loose adds impedance.
The fault current drops, the breaker may take longer to trip, and metal parts stay live for longer.
That is why electricians torque ground screws, use listed fittings on raceways and test the path rather than trusting it.
Forms an EGC can take
| Form | Where you see it | Notes |
|---|---|---|
| Bare copper wire in NM cable | Most modern house wiring | The familiar “ground wire” |
| Green or green/yellow insulated wire | In conduit runs and larger circuits | Color required by 250.119 for insulated EGCs 6 |
| Metal raceway such as EMT | Garages, basements, commercial work | Allowed under 250.118(4) 4 |
| Other listed metal raceways and armor | Various | All 250.118 types are metallic 5 |
Example: EGC sizes from published Table 250.122 cases
Table 250.122 sizes the EGC by the breaker or fuse protecting the circuit, and these rows appear in published EC&M and IAEI articles 2 3.
| Overcurrent device | Minimum copper EGC | Minimum aluminum EGC |
|---|---|---|
| 30 A | 10 AWG | Not given in the cited article |
| 40 A | 10 AWG | Not given in the cited article |
| 60 A | 10 AWG | Not given in the cited article |
| 200 A | 6 AWG | Not given in the cited article |
| 300 A (also used for 225 A) | 4 AWG | 2 AWG |
- 10 AWGCopper EGC for a 40 A breakerEC&M
- 6 AWGCopper EGC for a 200 A deviceIAEI
- 1.59×EC&M upsizing example: 10 AWG grows to 8 AWGEC&M
Two rules change these minimums. First, the EGC does not have to be larger than the circuit conductors. Second, if the circuit wires are upsized, for example for voltage drop, the EGC must grow in proportion; EC&M works an example where a 10 AWG EGC becomes 8 AWG 2.
Where EGCs are, and where they are missing
In homes wired with modern cable, every circuit has an EGC, but in homes wired before grounding conductors were standard, many circuits have only a hot and a neutral. Those circuits often have two-slot outlets, or three-slot outlets added later with nothing connected to the ground hole.
CPSC’s safety checklist says a three-prong adapter’s grounding tab or wire must connect to the outlet’s center screw, and that the feature exists to lessen fire and shock risk if a fault happens 10. It only works if the box itself is grounded, which an electrician must confirm.
Our research on housing age shows how many homes date from older wiring eras.
What the EGC does for you
What the EGC cannot do
An EGC trips a breaker only when fault current is large, so it cannot stop a small current through a person. Catching that small current is the job of a ground-fault circuit interrupter.
A broken EGC is silent, and OSHA warns that a break in the grounding system may occur without the user’s knowledge 8, so everything keeps working until a fault happens.
Ground wire vs neutral
Both connect to the same bar at the service, but they do different jobs. The neutral carries normal return current, while the EGC carries current only during a fault, so swapping or combining them puts current on metal parts.
What drives the cost of adding a ground
We do not print prices. Adding EGCs to an older home can mean new circuits, running a separate ground where the code permits, or GFCI protection as an allowed alternative for some replacements.
Wall access, the number of circuits and plaster versus drywall drive the cost, so see whole-house rewiring and the project cost tool.
How an electrician confirms or adds an EGC
Adding or repairing an equipment grounding conductor is licensed work and often needs a permit.
- Test outlets and equipment for a continuous ground path back to the panel.
- Find the cause of any open ground: loose splice, cut wire or missing conductor.
- Size any new EGC from Table 250.122 by the breaker rating 2.
- Connect it to every box, device green screw and the panel ground bar.
- Retest and, where required, pass inspection.
What owners can do
Warning signs of a missing or broken EGC
Signs include an outlet tester showing an open ground, a tingle from a metal appliance case, surge protectors with a “not grounded” light, or two-slot outlets in kitchens, baths or outdoors.
Do not use the ground as a neutral
Never connect a neutral lead to a ground wire, or a ground to a neutral outside the service panel. If an appliance case gives a tingle, unplug it and call an electrician, and if someone is injured, call 911.
Code rules
NEC Article 250, Part VI covers EGCs and Part VII their connections 7.
Section 250.118 lists the permitted types 5, and Section 250.119 lets EGCs be bare, covered or insulated, and requires insulated ones to be green or green with one or more yellow stripes 1.
Section 250.122(A) sets the minimum size from Table 250.122; the EGC need not be larger than the circuit conductors; and 250.122(B) requires proportional upsizing when the circuit conductors are upsized 2.
Local adoption of the NEC decides which edition’s wording applies.
EGC compared with related conductors
| Conductor | Color (typical) | Carries current when? |
|---|---|---|
| Hot (ungrounded) | Black, red or other non-white, non-green | Always, when a load runs |
| Neutral (grounded) | White or gray | Always, as return current |
| EGC | Bare, green or green/yellow | Only during a fault |
| Grounding electrode conductor | Usually bare copper | Surges and faults to earth |
Myths
- Myth The ground wire carries current all the time.
- Reality Only during a fault.
- Myth The earth trips the breaker.
- Reality The EGC back to the source does 4.
- Myth Any wire size works for ground.
- Reality Table 250.122 sets minimums by breaker rating 2.
- Myth A metal conduit can never be a ground.
- Reality Some raceways such as EMT are permitted EGCs 4.
Your state’s edition
What to do about ungrounded circuits
The right fix depends on the room and the budget.
- If Kitchen, bath, laundry or outdoor outlets
- Then GFCI protection at minimum; ask about new grounded circuits
- If Computers and electronics
- Then A grounded circuit, so surge protection works
- If Whole house on two-wire circuits
- Then Ask about rewiring in phases
- If Single open ground on a modern circuit
- Then Have the loose or broken connection found and fixed
Start with a test
An electrical inspection maps which circuits have a working EGC before you spend on fixes.
Questions about Equipment Grounding Conductor
What is the equipment grounding conductor?
It is the ground wire, or an approved metal raceway, that connects metal boxes, outlets and appliance frames back to the panel. It carries current only during a fault, and that current trips the breaker.
What color is the ground wire?
It is bare copper, or insulated green or green with one or more yellow stripes. Those colors are reserved for grounding under NEC 250.119, and must not be used for hot or neutral wires.
Does the ground wire carry current?
Not in normal operation. It carries current only when a fault happens, such as a hot wire touching a metal case, and that burst of current is what trips the breaker.
What size ground wire do I need?
The EGC is sized from NEC Table 250.122 by the breaker rating, and published examples include 10 AWG copper for a 40-amp device and 6 AWG copper for 200 amps. An electrician then applies the table and any upsizing rule.
Can metal conduit be the ground?
Yes, some types, since NEC 250.118 lists permitted EGC types, all metallic, and IAEI notes that EMT can serve as one, though the fittings must be tight because loose joints add impedance.
What happens if there is no ground wire?
A fault can leave a metal case live without tripping the breaker, and surge protectors lose their reference. GFCI protection is one code-allowed way to add safety on some older circuits, and an electrician can advise which applies.
Is ground the same as neutral?
No. They connect only at the service panel, where the main bonding jumper joins them. The neutral carries normal return current, and the ground carries current only during a fault, so mixing them elsewhere puts current on metal parts.
Why does my outlet tester say open ground?
The outlet has no working connection to an equipment grounding conductor, which may mean an older two-wire circuit or a broken connection. An electrician can find out which.
Does the ground wire need to be as big as the hot wires?
Not always. Table 250.122 often allows a smaller EGC than the circuit wires, and the EGC never needs to be larger than them. If the circuit wires are upsized, the EGC must be upsized in proportion.
Can I add a ground wire to an old outlet myself?
Grounding work is electrical work for a licensed electrician, and rules on homeowner work vary by place. This site does not give DIY steps, because an electrician can test and add a ground correctly.
Sources
- EC&M, Code Q&A: Identification of Circuit Conductors (200.6, 250.119), retrieved .
- Mike Holt, EC&M, Stumped by the Code? NEC Requirements for Sizing Equipment Grounding Conductors (2015), retrieved .
- L. Keith Lofland, IAEI Magazine, Sizing of Conductors Related to Grounding & Bonding (March 2021), retrieved .
- Michael Johnston, IAEI Magazine, Equipment Grounding for Safety (2008), retrieved .
- Mark Lamendola, EC&M, Understanding NEC Definitions for Grounding (May 2024), retrieved .
- EC&M, Code Q&A: NEC Requirements for Conductor Identification (2023), retrieved .
- Randy Barnett, EC&M, 10 Sure Ways to Tell the Difference Between Bonding & Grounding (Aug 2022), retrieved .
- OSHA Construction eTool, Electrical Incidents: Grounding, retrieved .
- Leviton, T5835-W 20A Tamper-Resistant USB Receptacle specifications (terminal identification), retrieved .
- US CPSC, Home Electrical Safety Checklist (Pub 513), retrieved .
- Texas Department of Licensing and Regulation, 2023 National Electrical Code is almost here, retrieved .
- Washington State Register WSR 25-23-069 (L&I adopts the 2026 NEC), retrieved .
Expert review
Written by the HyreElectrical Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Table 250.122 rows shown are only those printed in the cited EC&M and IAEI articles; unpublished cells are marked as not given. Types and colors follow EC&M (250.118, 250.119); function follows IAEI and OSHA. Owner guidance follows CPSC Pub 513. No DIY wiring; no prices under G-COST.
Suggest a correction. We fix errors and say what changed.