375 foot electrical run

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cablegeeks

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I have to make a 375 foot run and add a 20 amp breaker, customer wants to use MC. My max load would be 8 amps. What gauge conductor using 3/___ MC.
 
Here's how you can determine the size.

Here's how you can determine the size.

You need to decide what the maximum acceptable voltage drop %age is.
You need to know what the circuit voltage is, then you can figure the number of volts the %age is.
Then using Ohms law and the conductor resistance table (and double the circuit length (out and back)) you can calculate the voltage drop in various sizes of wire (starting with #12 CU since it protected by a 20A CB).
The smallest size wire with an acceptable voltage drop is the answer.

[Motor circuit could allow #14 if it meets voltage drop requirements.]

There is another way having to do with the conductance of CU (or AL) per circular mil but the above is pretty fast and less prone to error.
 
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cablegeeks said:
I have to make a 375 foot run and add a 20 amp breaker, customer wants to use MC. My max load would be 8 amps. What gauge conductor using 3/___ MC.
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Why don't you tell us what you come up with and how you come up with your answer. Then we will give you pointers.. :)
Since IMHO... This is something every sparky should know to do.. :)
 
What is the voltage? I expect that the size you need to get a reasonable voltage drop if the voltage is 120, will be a lot bigger than what you want to use.
 
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