Wire Sizes And Maximum Length Determination Chart Page 4
ADVERTISEMENT
1
2
3
4
5
6
7
8
9
10
11Wire Sizes and Maximum Length Determination
(7/5/2007)
Maximum Ampacities (Amperage Capacity) for Wire
Allowable ampacities of conductors (wires) in conduit, raceway, cable or directly buried,
based on ambient temperature of 86° F (30° C). NEC allows rounding up cable ampacity
to the next size standard fuse or breaker. Use this table for high voltages of 120 volts or
higher.
Maximum Ampacity for Copper
and Aluminum Wire
Copper
Aluminum
Wire Size
167° F (75° C)
194° F (90° C)
167° F (75° C)
194° F (90° C)
*14
20
25
.
*12
25
30
20
25
*10
35
40
30
35
8
50
55
40
45
6
65
75
50
60
4
85
95
65
75
2
115
130
90
100
1
130
150
100
115
1/0
150
170
120
135
2/0
175
195
135
150
3/0
200
225
155
175
4/0
230
260
180
205
* The national electric code (NEC) specifies that the over current protection device not
exceed 30A for 10 AGW wire, 20A for 12 AGW wire and 15A for 14 AWG wire.
Quick Overview
As electric current flows through wire, there is a loss in voltage. This loss is referred to
as IR voltage drop. Voltage (Drop) = Wire Resistance Times Amps of current (E=IR)
Calculating the voltage loss for a pair of wires gets a little complicated, so we have
constructed a quick look up table for what size wire you will need for your application.
The table below is for 12-volt ac or dc devices only. You just need to know the power in
Watts (VA), or Amps and the table will show how far you can go in feet for any size wire
pair listed. The table is based on a 10% loss of voltage on a pair of wires. This should
work for most 12-volt devices. Checking the manufacturer’s specifications, use the
maximum watts or current and be sure the minimum operational voltage is 10v or below.
The footage in the table is linear, a 20% loss would double the distance, or 5% would cut
it in half.
The table calculations are based on the ohms of the wire at 70oF. If the wire temperature
Page 4 of 11
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Life