What Size Ground Wire for a 45 Amp Breaker?
Verified against NEC 2023, checked against the 2026 edition · Last checked August 18, 2026
A 45 amp breaker or feeder needs an equipment grounding conductor of 10 AWG copper or 8 AWG aluminum · Table 250.122.
Common on this rating: HVAC equipment with a marked maximum breaker. Run with 8 AWG copper circuit conductors, the ground is 10 AWG copper.
Two different tables answer this question. A breaker, circuit or sub panel takes an equipment grounding conductor from Table 250.122, entered with the breaker rating. A service takes a grounding electrode conductor from Table 250.66, entered with the service conductor size. Mixing them up can change the answer by a size or more.
| Conductor | Size | Basis |
|---|---|---|
| Copper EGC | 10 AWG | Table 250.122 |
| Aluminum EGC | 8 AWG | Table 250.122 |
The EGC never needs to be larger than the circuit conductors · 250.122(A). Upsized circuit conductors mean a proportionally upsized EGC · 250.122(B). Parallel runs in separate raceways carry a full-size EGC in each raceway · 250.122(F).
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Common questions
- What size ground wire for a 45 amp breaker?
- An equipment grounding conductor of 10 AWG copper or 8 AWG aluminum, from Table 250.122. The EGC never needs to be larger than the circuit conductors · 250.122(A).
- What size ground wire for a 45 amp sub panel?
- The same as the breaker answer: 10 AWG copper or 8 AWG aluminum, sized by the 45 A feeder breaker per Table 250.122.
- Is the ground wire the same as the neutral?
- No. The grounded service conductor, the neutral, is a current-carrying conductor sized by 250.24(C) and 220.61. It is not the EGC of Table 250.122 and not the GEC of Table 250.66.
- What if my circuit conductors were upsized for voltage drop?
- If the circuit conductors were upsized for voltage drop, the EGC must be upsized in the same ratio of circular-mil area · 250.122(B).