Ground Wire Size for 80A Circuit
Equipment grounding conductor (EGC) sizing table
Equipment grounding conductors are sized based on the rating of the overcurrent device (breaker or fuse) protecting the circuit - not the wire ampacity or the actual load. NEC Table 250.122 provides the minimum sizes. Your 80A circuit row is highlighted:
| OCP Rating | Copper EGC | Aluminum EGC |
|---|---|---|
| 15A | 14 AWG | 12 AWG |
| 20A | 12 AWG | 10 AWG |
| 60A | 10 AWG | 8 AWG |
| 100A | 8 AWG | 6 AWG |
| 200A | 6 AWG | 4 AWG |
| 300A | 4 AWG | 2 AWG |
| 400A | 3 AWG | 1 AWG |
| 500A | 2 AWG | 1/0 AWG |
| 600A | 1 AWG | 2/0 AWG |
| 800A | 1/0 AWG | 3/0 AWG |
| 1000A | 2/0 AWG | 4/0 AWG |
| 1200A | 3/0 AWG | 250 kcmil |
| 1600A | 4/0 AWG | 350 kcmil |
| 2000A | 250 kcmil | 400 kcmil |
When does a 80A ground wire apply?
A 8 AWG copper equipment grounding conductor is required for any circuit protected by a 80A breaker or fuse. Common 80A circuits include large subpanels. The circuit conductors for a 80A circuit are typically 3 AWG using 3 AWG THHN.
At 80A, circuits typically use individual conductors (THHN/THWN-2) in conduit rather than NM-B cable. Run a separate 8 AWG copper green or bare equipment grounding conductor with the circuit conductors inside the conduit.
Key grounding rules
EGC vs GEC - two different things. The equipment grounding conductor (EGC, Table 250.122) runs with the circuit wires and bonds equipment back to the panel. The grounding electrode conductor (GEC, Table 250.66) connects the panel to the grounding electrode (ground rod, water pipe, or Ufer ground). These are different sizes sized from different tables for different purposes.
Upsizing rule (250.122(B)). When circuit conductors are upsized beyond the minimum required - typically for voltage drop on long runs - the EGC must be proportionally upsized. The formula: multiply the minimum EGC area by the ratio of the actual conductor area to the minimum required conductor area. In practice, if you double the circuit wire area, double the ground wire area.
Metallic conduit as EGC. EMT, RMC, and IMC are all recognized as equipment grounding paths per NEC 250.118. When using metallic conduit, a separate green ground wire is not technically required - the conduit itself serves as the ground path. However, many electricians and inspectors prefer a separate ground wire as redundancy, and some local codes require it.
Multiple circuits in one conduit. When multiple circuits share a single conduit, you need only one EGC sized for the largest overcurrent device protecting any circuit in that conduit (NEC 250.122(C)). You do not need a separate ground for each circuit.
Installation requirements
Color coding: Equipment grounding conductors must be green, green with yellow stripe, or bare copper per NEC 250.119. Do not use any other color for a grounding conductor. White and gray are reserved for neutrals.
Continuity: The ground path must be continuous from the equipment being grounded all the way back to the service panel ground bus. Every splice, connection, and termination must be listed and properly torqued. A loose ground connection defeats the entire safety purpose.
Ground rod requirements: At the main service panel, a grounding electrode conductor (GEC) connects to ground rods. Two ground rods are required if a single rod does not achieve 25 ohms or less resistance (NEC 250.56). Rods must be at least 8 feet long and driven full depth.
Frequently asked questions
What size ground wire for a 80 amp circuit?
8 AWG copper or 6 AWG aluminum per NEC Table 250.122. This is the minimum equipment grounding conductor. If you upsize the circuit conductors for voltage drop, the ground must be proportionally upsized per 250.122(B).
Is the ground wire in NM-B cable big enough for a 80A circuit?
At 80A, you typically use individual THHN conductors in conduit rather than NM-B cable. Run a separate 8 AWG copper green or bare ground wire with the circuit conductors.
Can I use metallic conduit as the ground instead of a wire?
Yes. EMT, RMC, and IMC are recognized as equipment grounding paths per NEC 250.118. The conduit itself serves as the ground conductor. However, many electricians run a separate green wire inside metallic conduit as redundancy, and some local jurisdictions require it.
What happens if the ground wire is too small?
An undersized ground wire may not carry enough fault current to trip the breaker quickly during a ground fault. This can leave equipment energized at dangerous voltages, creating shock and fire hazards. Always use the minimum size from NEC Table 250.122 or larger.
Related guides
- 80A wire sizing guide
- Ampacity tables - all wire sizes
- NEC Article 250: Grounding & bonding
- Ground rod vs UFER ground
- Ampacity calculator
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NEC 2023 references verified April 2026