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Old 04-27-2012, 11:36 AM   #16
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Distance of GFCI Breakers?


You would need 2 gauge wire the whole way to give you 15 amps at 120 volts 700 feet away (3-1/2% voltage drop).

While you might be thinking of tolerating a little more voltage drop, say, 5% with 4 gauge wire the whole way, keep in mind that there may be additional voltage drop from the utility pole to the house and from the house to the barn, depending on other barn usage such as cow milkers and chicken incubators. Adding in the voltage drop from barn to the fields we are dealing with here and any voltage drop in an orange extension cord you might bring out there and need, the total voltage drop may degrade the operation of power tools.

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Last edited by AllanJ; 04-27-2012 at 11:43 AM.
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Old 04-27-2012, 01:42 PM   #17
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Distance of GFCI Breakers?


I must have missed the part where he said it was 700 feet, it says 350 feet in the original post. The number 6 is plenty big enough for that. To be safe you may want to run number 10 out from the first waterer to the second.

As for the low voltage thing there's no way that will work. You would need a huge cable to carry 24v that far. Remember voltage drop is calculated as a percentage so it's a lot easier to drop 5% off 24v's than it is to drop it off 110v.
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Old 04-27-2012, 02:22 PM   #18
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Distance of GFCI Breakers?


The topic was first started here:
Outdoor Subpanel 350' feet away from Barn

The OP started by discussing a proposed 350' trunk line (2 conductor 120 volt) from a barn subpanel to somewhere in the middle of a field for a proposed sub-subpanel. Then he corrected himself to say there was a second 350' from the sub-subpanel to yet further off in the middle of the field. This latter segment is the latest subject being discussed.

We are currently concluding that a junction box can be used instead of the sub-subpanel out in the field.

The longest run to be installed is thus 700' one way or 1400' round trip. From the halfway point two other branches go off in different directions. You need to consider the round trip when figuring voltage drop.

Let's say for a given section of wire (it has resistance of X ohms) there is a 1 volt voltage drop at 120 volts (slightly less than 1%) when 1 ampere is flowing. If we used 12 volts for that wire and 1 amp was flowing, we would also get a 1 volt voltage drop which is about 8%. Now for 1 ampere at 120 volts we need 10 amperes at 12 volts to get the same number of watts. Ten amperes going down that same wire would result in losing 10 volts to voltage drop. Losing 10 out of 12 volts is losing 83 percent.

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Last edited by AllanJ; 04-27-2012 at 02:45 PM.
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