NEC Tables · Ampacity

NEC Table 310.16 — Conductor Ampacity

Allowable ampacities of insulated conductors (no more than three current-carrying in a raceway), answered in two taps — then the full chart and the rules that change the number.

Free · NEC 2023 · Updated
65 A
6 · 75°C (167°F)
base ampacity — apply 310.15 correction and adjustment factors before sizing
Exam trap14, 12, and 10 AWG copper are capped by 240.4(D) at 15, 20, and 30 A for overcurrent protection, no matter what this table says. The most-missed lookup in our question bank.

Table 310.16 is the most-used table in the NEC and the most-tested on the journeyman exam. Pick a conductor size and a column to get the base ampacity, then apply the 310.15 correction and adjustment factors — and remember that terminations, not the wire, usually decide which column you may use.

Size (AWG/kcmil)CopperAluminum / Cu-clad aluminum
Size AWG or kcmil60°C (140°F)75°C (167°F)90°C (194°F)60°C (140°F)75°C (167°F)90°C (194°F)
18*——14———
16*——18———
14*152025———
12*202530152025
10*303540253035
8405055354045
6556575405055
4708595556575
385100115657585
2951151307590100
111013014585100115
1/0125150170100120135
2/0145175195115135150
3/0165200225130155175
4/0195230260150180205
250215255290170205230
300240285320195230260
350260310350210250280
400280335380225270305
500320380430260310350
600350420475285340385
700385460520315375425
750400475535320385435
800410490555330395445
900435520585355425480
1000455545615375445500
1250495590665405485545
1500525625705435520585
1750545650735455545615
2000555665750470560630
Notes that change the answer — 310.16

Notes:

1. Section 310.15(B) shall be referenced for ampacity correction factors where the ambient temperature is other than 30°C (86°F).

2. Section 310.15(C)(1) shall be referenced for more than three current-carrying conductors.

3. Section 310.16 shall be referenced for conditions of use.

*Section 240.4(D) shall be referenced for conductor overcurrent protection limitations, except as modified elsewhere in the Code.

Values derived from the 2023 National Electrical Code for exam study. Verify installations against the adopted code and local amendments.

Race your codebook — 3 lookups on this table

Q1

A fire alarm control panel powers 16 AWG Class 1 remote-control conductors run to field devices. What is the maximum standard overcurrent device rating permitted to protect these conductors, and which section of Article 724 sets this limit?

  1. A 724.49
  2. B 724.43
  3. C 724.51
  4. D 724.45
Show answer & explanation

Correct: B — 724.43

724.43 sets the specific overcurrent maximums for small Class 1 conductors — 7 A for 18 AWG and 10 A for 16 AWG — and requires 14 AWG and larger to be protected per conductor ampacity without 310.15 adjustment/correction factors. 724.45 only addresses where the overcurrent device may be located, not its rating, and 724.49 covers conductor sizing/insulation, not overcurrent protection.

Q2

An installer is sizing the branch-circuit overcurrent protective device for 12 AWG Class 1 power-limited conductors and wants to know whether the standard 310.15 ampacity adjustment and correction factors apply when calculating the conductor's ampacity for this purpose. Which section answers this?

  1. A 724.51
  2. B 724.43
  3. C 724.49
  4. D 724.40
Show answer & explanation

Correct: B — 724.43

724.43 expressly states that for 14 AWG and larger Class 1 conductors, overcurrent protection is based on conductor ampacity without applying the 310.15 adjustment and correction factors. 724.51 covers ampacity adjustment for conductor fill in cable trays/raceways generally, not the overcurrent-sizing exemption itself, and 724.40 just classifies Class 1 circuits.

Q3

Type AC cable containing two-conductor 12 AWG homeruns is going to be embedded in sealing foam along with three other AC cables at a point where they pass through a fire-rated wall, with no spacing maintained between them. Which section requires that the ampacity of each conductor be adjusted for this grouping?

  1. A 320.80(B)
  2. B 320.80(A)
  3. C 320.30(D)
  4. D 320.104
Show answer & explanation

Correct: B — 320.80(A)

320.80(A) specifically addresses AC cable in contact with thermal insulation, caulk, or sealing foam, requiring adjustment per Table 310.15(C)(1) when more than two multiconductor cables are bunched without spacing; 320.80(B) instead governs cable tray installations, which don't apply here.

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