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What Size Breaker for 3 AWG Wire?

For 3 AWG wire under the displayed non-receptacle defaults, the largest common breaker is 100 A for copper and 80 A for aluminum. The aluminum result depends on the next-size-up path, so aluminum substitutions and lug limits need a deliberate check.
Wire
3 AWG
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Large feeder
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Compatibility calculator

Breaker Starting Point

Maximum common breaker sizes under common conditions. Derating or receptacle limits can reduce these.

MaterialConductorLargest common breakerAssumptions
Copper3 AWG copper100 A90 C insulation, 75 C lugs, 86 F, 3 current-carrying conductors, non-receptacle circuit default
Aluminum3 AWG aluminum80 A90 C insulation, 75 C lugs, 86 F, 3 current-carrying conductors, non-receptacle circuit default
What Size Breaker for 3 AWG Wire? under common non-receptacle defaults: 90 C insulation, 75 C lugs, 86 F ambient, no more than three current-carrying conductors, and next-size-up checks only where eligible.

What 3 AWG ChangesAt 3 AWG, copper lands on the clean 100 A feeder step while aluminum reaches 80 A through the non-receptacle next-size-up path from 75 A usable ampacity. This page is the handoff from appliance-sized conductors into feeder work, where lugs, load calculation, voltage drop, and AHJ review carry more weight.

Check breaker and wire together

Adjacent Wire Sizes

See whether stepping one conductor size changes the maximum standard breaker.

WireCopper max breakerAluminum max breaker
4 AWG90 A70 A
3 AWG (this page)100 A80 A
2 AWG125 A90 A
Largest common breakers for 3 AWG and neighboring published wire sizes under the same defaults.

3 AWG Starts the Large-Feeder Band

Large feeder context for 3 AWG wire.

A 3 AWG breaker-size search usually points to a 100 A feeder idea, a panel replacement, or a field check after someone found larger wire than the usual appliance sizes.

Under the displayed defaults, 3 AWG copper reaches a 100 A maximum breaker. 3 AWG aluminum reaches 80 A, so an aluminum feeder cannot borrow the copper answer just because the AWG number matches.

Field Checks for This Wire Size

Checks that matter in this conductor band — not a generic breaker list.

  • Separate the 100 A result

    The 100 A maximum belongs to 3 AWG copper under these defaults. The 3 AWG aluminum row returns 80 A.

  • Name the aluminum next-size-up step

    The 80 A aluminum maximum comes from 75 A usable ampacity through the non-receptacle next-size-up default. Confirm that allowance before using the rounded result.

  • Check 60 C equipment

    Equipment limited to 60 C can reduce the conductor ampacity before any breaker is selected. Confirm the actual terminal rating at both ends.

  • Verify feeder load first

    A 100 A breaker maximum does not prove the feeder is correctly sized. Run the load calculation and voltage-drop check for the actual run.

  • Confirm lug range and material

    Panel, disconnect, and equipment lugs must accept 3 AWG in the chosen material. Listed aluminum lugs are required for aluminum conductors.

3 AWG Breaker FAQs

What size breaker for 3 AWG wire?
Under the displayed non-receptacle defaults on this page, 3 AWG copper has a 100 A maximum breaker and 3 AWG aluminum has an 80 A maximum breaker.
Can 3 AWG aluminum use a 100 A breaker?
No under these defaults. The 100 A result belongs to copper. The 3 AWG aluminum row returns an 80 A maximum breaker, and that 80 A value depends on next-size-up eligibility.
Why is 3 AWG copper a common 100 A check?
The displayed 75 C path reaches 100 A for copper under common feeder defaults. That still assumes the real installation matches the listed conditions.
Can I use this page as final approval for a feeder?
No. Treat it as a compatibility starting point only. Feeder work still needs load calculation, terminal temperature, conductor material, raceway fill, voltage drop, equipment listings, and AHJ review.