14 AWG ampacity by temperature column
| Conductor | 60°C | 75°C | 90°C | 240.4(D) |
|---|---|---|---|---|
| Copper | 15 A15 A breaker | 20 A15 A breaker | 25 A15 A breaker | 15 A |
Ampacities are NEC Table 310.16 values for a conductor at 30°C ambient in a raceway, cable, or direct burial with three or fewer current-carrying conductors. Ambient correction and conductor adjustment are applied to these numbers before the 240.4(D) cap is checked, never after it.
What size breaker for 14 gauge wire
- 14 AWG copper: 15 A, held there by 240.4(D)(3).
240.4(D)(3) caps overcurrent protection on 14 AWG copper at 15 A, so the device is 15 A whatever the terminations are marked and whatever the 15 A in the 90°C column becomes after correction. The higher columns are derating arithmetic: they describe how much current the insulation survives at 30°C ambient with three current-carrying conductors, not how large a breaker the conductor will protect. 334.80 and 340.80 hold NM-B and UF-B cable to the 60°C column whatever the terminals are marked, so a cable assembly is read from the left-hand column while conductors in raceway are read from the column the equipment is listed for.
What 14 gauge wire is used for
- 15 A lighting and general-purpose receptacle branch circuits
- Switch legs, smoke detector interconnect, and fixture whips
- Control wiring inside listed equipment
Fourteen gauge is the smallest branch-circuit conductor the code allows, and one of the three sizes whose 240.4(D) cap equals its 60°C ampacity. That match is why 14/2 NM-B is a 15 A cable and nothing else. It is barred from the circuits that require 20 A: the two or more kitchen small-appliance branch circuits in 210.11(C)(1), the laundry circuit in 210.11(C)(2), and the bathroom circuit in 210.11(C)(3).
Table 310.16 lists no aluminum conductor at 14 AWG, so this size is copper or copper-clad aluminum only; the smallest aluminum conductor in the table is 12 AWG, and 240.4(D)(4) caps that at 15 A. Box fill is 2.00 cubic inches per counted conductor under Table 314.16(B), the tightest of the common sizes, which is why extending an existing circuit into a new device is where box fill usually fails.
The values in the 75°C and 90°C columns are derating figures. Ambient correction and the adjustment for more than three current-carrying conductors are applied to those numbers, and 240.4(D)(3) then holds the protection at 15 A whatever the corrected ampacity reaches. A 14 AWG conductor can lose a third of its table ampacity to heat and bundling and still sit on the same breaker, which is what makes it usable in a packed cable or a hot attic.
Grounding with 14 AWG
As an equipment grounding conductor, 14 AWG is sized from the overcurrent device rather than from the phase conductors. Table 250.122 names 14 AWG copper on the 15 A row. 250.122(B) raises the ground in the same proportion as the phase conductors when they are increased for voltage drop, and 250.122(A) caps it at the size of the conductors it runs with.
Table 250.66 never lists 14 AWG as a grounding electrode conductor, so it is used for phase conductors, neutrals, and equipment grounds rather than for the connection to earth.
Voltage drop and run limits
Chapter 9 Table 8 lists 14 AWG copper at 3.14 ohms per 1000 ft at 75°C and aluminum at 5.17 ohms per 1000 ft. Resistance is what a voltage-drop calculation multiplies by current and length, so a conductor twice as long drops twice the volts.
| Conductor | 120 V single phase | 240 V single phase | 240 V three phase |
|---|---|---|---|
| 14 AWG copper at 15 A | 35 ft | 75 ft | 85 ft |
NEC 210.19(A)(1) Informational Note 4 recommends keeping branch-circuit drop at or below 3%. The lengths above are floored to the nearest 5 ft so a listed length never exceeds the computed limit, and they leave reactance out, which makes a large conductor in steel raceway fall short. Halving the current doubles the distance.
Box fill with 14 AWG
Table 314.16(B) allows 2.00 cubic inches per counted conductor at this size. Every conductor that originates outside a box and terminates or is spliced inside it counts once, each device yoke counts as two of the largest conductor in the box, and all the equipment grounding conductors together count as one. The total is compared against the box volume from Table 314.16(A). Table 314.16(B) stops at 6 AWG, so a larger conductor is sized by the pull and bend rules in 314.28 instead.
Where 14 AWG sits
| Conductor | 60°C | 75°C | 90°C |
|---|---|---|---|
| 14 AWG copper | 15 A | 20 A | 25 A |
| 12 AWG copper | 20 A | 25 A | 30 A |
14 AWG questions
- How many amps can 14 gauge wire handle?
- 14 AWG copper handles 15 A at 60°C, 20 A at 75°C, and 25 A at 90°C. The 60°C value is also the protection limit, because 240.4(D)(3) caps the device at 15 A after any correction and adjustment, so the higher columns are for derating rather than for a bigger breaker. No aluminum conductor is listed at this size.
- What size breaker for 14 gauge wire?
- 15 A. 240.4(D)(3) caps overcurrent protection at 15 A, and the cap applies after ambient correction and conductor adjustment.
- What is 14 gauge wire used for?
- 15 A lighting and general-purpose receptacle branch circuits; switch legs, smoke detector interconnect, and fixture whips; control wiring inside listed equipment. Fourteen gauge is the smallest branch-circuit conductor the code allows, and one of the three sizes whose 240.4(D) cap equals its 60°C ampacity. That match is why 14/2 NM-B is a 15 A cable and nothing else. It is barred from the circuits that require 20 A: the two or more kitchen small-appliance branch circuits in 210.11(C)(1), the laundry circuit in 210.11(C)(2), and the bathroom circuit in 210.11(C)(3).
- What size ground wire with 14 gauge conductors?
- 14 AWG copper is the equipment grounding conductor for 15 A circuits in Table 250.122. The ground is sized from the overcurrent device rather than from the phase conductors, and 250.122(B) raises it in the same proportion if the phase conductors are increased for voltage drop. It never has to be larger than the conductors it runs with.