wire size

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  #1  
Old 10-05-02, 06:10 PM
B
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wire size

where can I find wire size for;

30 amp
40 amp
50 amp
60 amp
70 amp


I should know this but brain ain't working right.
 
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  #2  
Old 10-05-02, 06:43 PM
J
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It's not that simple. The ampacity of wire depends on a lot of factors other than gauge. But let me give you one answer that might be the one you want.

Assuming copper wire, 60-degree insulation (or a cable type that requires use of the 60-degree numbers), ambient temperature of 86-degrees F, not more than 3 current-carrying conductors in a raceway, and not more than 2000 volts:

30 amps can be carried by 10-gauge wire or larger.
40 amps can be carried by 8-gauge wire or larger.
50 amps can be carried by 6-gauge wire or larger.
60 amps can be carried by 4-gauge wire or larger.
70 amps can be carried by 4-gauge wire or larger.

Change any of my assumptions and the answer may be different. There are also different numbers for service and feeder wires as opposed to branch wires. When the load is a motor, the answer may be different too. Sometimes ranges are computed differently too. Finally, there are certain situations where the breaker size may be greater than the ampacity.

So you can see that a simple table isn't really that useful. You have to design the wire for the particular application.
 
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