Allowable Ampacity/Circuit Breaker Size of Copper Insulated Conductors
Rated 0-2000 Volts, 60 to 90 C (140-194 F)
Not more than 3 conductors in raceway or cable or
earth(direct-bury), based on Ambient Temperature of 30C (86F)
Size................. Temp Rating of Conductor
AWG/
kcmil
60C
(140F)
75C
(167F)
90C
(194F)
  Types
TW, UF
Types
RH, THHW,
THW,THWN
Types
RHH, THHN,
THHW, THHW
14 15 15 25
12 20 20 30
10 30 35 40
8 40 50 55
6 55 65 75
4 70 85 95
3 85 100 110
2 95/100 115 130
1 110 130 150
1/0 125 150 170
2/0 145/150 175 195
3/0 165/175 200 225
4/0 195/200 230 260
250 215 255 290
300 240 285 320
350 260 310 350
400 280 335 380
500 320 380 430
600 355 420 475
1000 455 545 615
1500 520 625 705
AWG/
kcmil
60C
(140F)
75C
(167F)
 
90C
(194F)
 


Common thermoplastic-insulated conductors

Type Max. operating temperature Application
TW 60 C (140 F) Dry and wet locations
THW 75 C (167 F) Dry and wet locations
THWN 75 C (167 F) Dry and wet locations

Conductor Type Designations:

H= 75
, 15C temperature rise over 60C
HH= 90C, 30C temperature rise over 60C
N= Outer nylon jacket or equivalent coating
R= Rubber insulation
T= Thermoplastic insulation
U= Underground use
W= Moisture resistant
X= Cross-linked synthetic polymer insulation

[Ref: NEC, Table 310-16]

Notes:
1. AWG= American Wire Gauge.For a complete listing on allowable Ampacity of conductors, consult NEC, Table 310-16.
2. For Aluminum wires, see NEC, Table 310-16.
3. See NEC, Table 310-16 for footnotes that modify the information in the table.
4. ROMEX (Nonmetallic Sheathed Cable) should be sized to 60C column of NEC, Table 310-16. 
5. Service Conductors are sized for wire types listed in NEC , Table 310-16, footnote #3, for 120/240, 3-wire, 1-phase Dwelling Service & Feeders.
6. Note: At present time, U.L. lists Circuit Breakers (CB's) and equipment rated at 100 amps or less based on the use of conductors sized to the 60C rating in the NEC. For Circuit Breakers and equipment rated over 100 amps are based on the use of conductors sized to the 75C rating in the NEC.
7. Higher temp. rated conductors may be used, but the size of the conductors must be determined on the basis of the 60C Ampacity on circuits 100 amps or less. NEC 110-14(c).
8. Conductors Type: See NEC, Table 310-13.
9. For conductors identification, see
NEC 300-12.