Determine Wire Size






Determine wire size using table 310.16 NEC2008 on page 70-148. Whether you are doing home electrical repair or on a electrical design job, simply calculate amperage (current) flow through the circuit and then apply the table.

Table 310.16

Allowable ampacities of Insulated Conductors rated 0 through 2000 Volts, 60°C through 90°C (140°F through 194°F), Not more than three Current-Carrying Conductors in Raceway, Cable, or Earth (Directly Buried), Based on Ambient Temperature of 30°C(86°F)

SIZE AWG OR KCMIL COPPER COPPER COPPER ALUMINUM ALUMINUM ALUMINUM SIZE AWG OR KCMIL
_ TYPE TW,UF TYPES RHW
,THHW,THW,
THWN,XHHW
USE,ZW
RHW-2,THHN
THHW,THW-2
(90°C)
TYPES TW,UF
(60°C)
TYPES RHW
THHW,THW
THWN,XHHW
USE
TYPES TBS,SA
SIS,THHW
SIZE AWG OR KCMIL
18
16
14
12
10
8
_
_
20
25
30
40
_
_
20
25
35
50
14
18
25
30
40
55
_
_
_
20
25
30
_
_
_
20
30
40
_
_
_
25
35
45
_
_
_
12
10
8
6
4
3
2
1
55
70
85
95
110
65
85
100
115
130
75
95
110
130
150
40
55
65
75
85
50
65
75
90
100
60
75
85
100
115
6
4
3
2
1
1/0
2/0
3/0
4/0
125
145
165
195
150
175
200
230
170
195
225
260
100
115
130
150
120
135
155
180
135
150
175
205
1/0
2/0
3/0
4/0
250
300
350
400
500
215
240
260
280
320
255
285
310
335
380
290
320
350
380
430
170
190
210
225
260
205
230
250
270
310
230
225
280
305
350
250
300
350
400
500
600
700
750
800
900
335
385
400
410
435
420
460
475
490
520
475
520
535
555
585
285
310
320
330
335
340
375
385
395
425
385
420
435
450
480
600
700
750
800
900
1000
1250
1500
1750
2000
435
495
520
545
560
545
590
625
650
665
615
665
705
735
750
375
405
435
455
470
445
485
520
545
560
500
545
585
615
630
1000
1250
1500
1750
2000


Apply table 310.16

Assume the current calculated result is 14A, cable type is copper THHN, insulated conductors rated at 90° C, Ignored some other factors,based on the table, wire size is 18 AWG. For practical safety application, recommended power wire size should be bigger than 12 AWG.

wire electrical size calculator

DETERMINE CONDUIT SIZE

ELECTRICAL WIRE SIZE

ELECTRICAL FORMULAS

MINIMUM CONDUCTOR SIZE

GENERATOR SIZING

TRANSFORMER SIZING

STARTER SIZING

CALCULATOR

Reference

National Electrical Code 2008

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