Hi, just wondering what the max amp load I can run using 8gauge copper wire? The reason I am using 8gauge is I picked up 1000' for 5 bucks. If it's still too small I'll use something else but the price was too good to pass up.
The run is about 125 feet and will be buried in conduit. This is going to a second garage I just built.
thanks
In the US the NEC is the governing regulation. I don't have a copy handy but to the best of my recollection 8 GA copper = 40 A.
HTH.
To start off with the wire should be suitable for wet locations. The marking should say something like THWN. W as in wet. Underground installations are considered to be wet locations. The answer to your question depends on outside factors. What is the temperature rating of the boxes this wire will be connected to? Boxes rated at 100 amps or less or marked for #14 through 1 AWG are generally rated at
60º C unless otherwise marked. #8 is rated at 40 amps at 60º, 50 amps at 75º. Take 80% of those figures as wire isn't supposed to be loaded to more than 80% of rated capacity. The voltage drop formula I used gave an answer of 39 amps. 32 amps is the maximum if you have to use the 60º rating. 39 amps is the maximum if you can use the 75º rating.Dean
You could run thirty amperes of fully balanced 120/240 volt load; that is 7200 Volt Amperes; on the number eight wiring without exceeding the
3% maximum that is considered as good practice for feeders. In other words that gauge could be used to supply four fifteen ampere 120 volt circuits that were all evenly loaded.-- Tom H
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