Heater Hookup Wire
| The
use of this table for establishing ampacity ratings is an inexact
procedure. This table should only be used as a starting point
when establishing ratings for any given situation. Values may
be lesser or greater than those given in the table because of
the influence of installation method, environment, number of
conductors, conductor composition and size, ambient temperatures,
insulation types, etc. It is recommended that design engineers
desiring accurate ampacity data closely study the 1990 National
Electrical Code Handbook Article 310-15-310-84. Additional information
can be derived from AIEE, paper number 57-660, “The calculation
of the temperature rise and load capability of cable systems”
by J. H. Neher and M. H. McGrath. This paper was presented to
the AIEE general meeting in Montreal, Quebec, Canada on June
24-28,1956 and was published in the “AIEE transactions,” part
3 (power apparatus and systems), Volume 76, October, 1957, pp.
752-772. |
|
Conductor Types:
tc = tinned copper
npc = nickel plated copper
npi = nickel plated iron
A-nickel = Type ‘A” 100% nickel
Current Carrying Capacity Base Temperature
at 40°C (Values tabulated are In Amperes)
| Wire
Gage AWG |
Conductor
Type |
| 200°C |
250°C |
250°C |
250°C |
450°C |
450°C |
| tc,npc |
npc-7% |
A-nickel
|
npi |
npc-27% |
A-nickel |
|
24
|
7.2
|
8.0
|
4.0
|
3.3
|
9.0
|
4.3
|
|
22
|
9.6
|
10.8
|
5.0
|
4.4
|
12.0
|
5.6
|
|
20
|
14.0
|
15.0
|
7.0
|
6.0
|
18.0
|
8.0
|
|
18
|
18.0
|
20.0
|
9.4
|
8.0
|
23.0
|
11.0
|
|
16
|
24.0
|
26.0
|
12.0
|
11.0
|
30.0
|
14.0
|
|
14
|
36.0
|
39.0
|
18.0
|
16.0
|
45.0
|
21.0
|
|
12
|
45.0
|
49.0
|
23.0
|
20.0
|
56.0
|
26.0
|
|
10
|
60.0
|
66.0
|
31.0
|
27.0
|
75.0
|
35.0
|
|
8
|
83.0
|
91.0
|
-
|
-
|
104.0
|
49.0
|
|
6
|
110.0
|
121.0
|
-
|
-
|
138.0
|
65.0
|
Temperature Correction Factors For ambient temperatures other than
40°C (104°F), multiply the ampacities shown above by the appropriate
factor shown below
| Ambient
|
Temperature |
Wire
Temperature Rating |
| °C |
°F
|
200°C |
250°C |
450°C |
|
41-50
|
106-122
|
0.97
|
0.98
|
0.99
|
|
51-60
|
124-140
|
0.94
|
0.95
|
0.99
|
|
61-70
|
142-158
|
0.90
|
0.93
|
0.96
|
|
71-80
|
160-176
|
0.87
|
0.90
|
0.95
|
|
81-90
|
177-194
|
0.83
|
0.87
|
0.90
|
|
91-100
|
195-212
|
0.72
|
0.85
|
0.92
|
|
101-120
|
213-248
|
0.71
|
0.79
|
0.89
|
|
121-140
|
249-284
|
0.61
|
0.71
|
0.86
|
|
141-160
|
285-320
|
0.50
|
0.65
|
0.84
|
|
161-180
|
321-356
|
0.35
|
0.58
|
0.81
|
|
181-200
|
357-392
|
-
|
0.49
|
0.78
|
|
201-225
|
393-437
|
-
|
0.35
|
0.74
|
|
226-250
|
439-482
|
-
|
-
|
0.69
|
|
251-275
|
483-527
|
-
|
-
|
0.65
|
|
276-300
|
528-572
|
-
|
-
|
0.60
|
|
301-325
|
573-617
|
-
|
-
|
0.55
|
|
326-350
|
618-662
|
-
|
-
|
0.49
|
|
351-375
|
663-707
|
-
|
-
|
0.42
|
|
376-400
|
708-752
|
-
|
-
|
0.34
|
Example: The
current carrying capacity (ampacity) rating of a 16 AWG 200°C npc
conductor at 40°C is 24.0 Amps.
|
|
|
|
