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Maximum Ampacities for Wire

The following table shows the allowable ampacities of conductors (wires) in conduit, raceway, cable or directly buried, based on ambient temperature of 30 degrees Celsius (86 degrees Fahrenheit).  National Electrical Code (NEC) allows rounding up cable ampacity to next size standard fuse or breaker.

     

    Wire Size Copper Conductor Temp Rating Aluminum Conductor Temp Rating

    75 Degrees Celsius (167 Degrees Fahrenheit) 90 Degrees Celsius (194 Degrees Fahrenheit) 75 Degrees Celsius (167 Degrees Fahrenheit) 90 Degrees Celsius (194 Degrees Fahrenheit)
    *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

    NEC specifies that the over-current protection device not exceed 30A for 10 AWG wire, 20A for 12 AWG wire and 15A for 14 AWG wire.


    For ambient temperatures above, multiply the allowable ampacities by  the correction factor listed under the insulation temperature rating below:


    Temperature range 75 Degrees Fahrenheit Insulation 90 Degrees Fahrenheit Insulation
    31-35 Degrees Celsius 87-95 Degrees Fahrenheit 0.94 0.96
    36-40 Degrees Celsius 96-104 Degrees Fahrenheit 0.88 0.91
    41-45 Degrees Celsius 105-113 Degrees Fahrenheit 0.82 0.87
    46-50 Degrees Celsius 114-122 Degrees Fahrenheit 0.75 0.82
    51-55 Degrees Celsius 123-131 Degrees Fahrenheit 0.67 0.76
    56-60 Degrees Celsius 132-140 Degrees Fahrenheit 0.58 0.71

    Recommended Inverter Cable and Overcurrent Protection

    Use this table to decide cable size and fuse or breaker size for common inverter models.  Smaller cable sizes can be used if fuse or breaker size is reduced but this can cause problems if the inverter is run near its maximum output wattage.  Larger cables may be necessary if the distance from the inverter to the battery is greater than 10 feet.


    Inverter Voltage Continuous Watts Maximum Inverter Input Amps Fuse Size (amps) Circuit Breaker (amps) Wire Size (AWG)
    12 Volt 600
    800
    1000
    1500
    2400
    2500
    2800
    3000
    80
    107
    134
    200
    320
    334
    382
    400
    80
    110
    200
    300
    400
    400
    400
    400
    80
    110
    175
    250
    250
    250
    250
    250
    2
    2
    2/0
    4/0
    4/0
    4/0
    4/0
    4/0
    24 Volt 600
    800
    1000
    1500
    2400
    2500
    3000
    3500
    4000
    40
    54
    67
    100
    160
    167
    200
    230
    265
    50
    75
    80
    110
    200
    200
    300
    300
    300
    50
    75
    100
    110
    175
    175
    250
    250
    250
    8
    4
    2
    2/0
    2/0
    2/0
    4/0
    4/0
    4/0
    48 Volt 3000
    3600
    4000
    5500
    76
    90
    148
    185
    110
    110
    200
    400
    110
    110
    175
    250
    2/0
    2/0
    2/0
    4/0


    For more info and recommendations on pairing the right fuse and cables to your DC to AC power inverter, watch Jeff’s YouTube video below:


    DC to AC Inverter Fuse and Cable Sizing


     
     


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