what wire size ?

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Kentuckian

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I'm new to the forum and new to electrical field, so try and take it easy one me lol.
I need to supply a 120v 20A circuit for a refrigerator or possibly 2 . The closest power supply is 380ft away. If what I have came up with is correct I will need to run 6awg? I assume I could make a junction box above the outlet and wire the outlet up with 12ga wire? Thanks
 
Kentuckian said:
I'm new to the forum and new to electrical field, so try and take it easy one me lol.
I need to supply a 120v 20A circuit for a refrigerator or possibly 2 . The closest power supply is 380ft away. If what I have came up with is correct I will need to run 6awg? I assume I could make a junction box above the outlet and wire the outlet up with 12ga wire? Thanks
Click to expand...

I'll need a little bit more info to help you out. Is it one refrigerator or two? That makes a big difference. If they are full size refrigerators they will need to be on dedicated circuits so you will end up running two circuits. Secondly it would be helpful to know the actual amp draw on the equipment as this will affect your voltage drop. For example - If you are pulling 16 amps on a 20A circuit (80% rule) then with #6's (copper) your voltage drop would be about 5% 380 feet away. That's not too great. The rule of thumb fro branch circuits is 3% drop.

- Drew
 
With #6 wire and 16 amps of load, I am getting a 5% VD. To get below 3%, you would need #4. Yes you can reduce to #12 in a JB. Welcome to the forum.
 
Voltage drop = 2 x lenght x amperage needed(20 amps in this case & circuit size) x K (12 for CU & 21 for AL is common) / circular mills (Table 8 Chapter 9)
as rule of thumb never exceed 5% -- 120v x .05 = 6 volts 3% max is recommended - time to learn so I'll let you do the math. Hopefully your refrigerator does not require a dedicated 15 amp circuit -- another code section
 
what wire size ?

The refrigerator will be on its own circuit.
FL A is 6A. Thanks for clearing it up that NEC recommends no more than 3% I was thinking it was 5%. So with 4ga wire and an fla rating at 6A. This should be fine on a 20a circuit?
 
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Since the refrigerator is a relatively constant load, I would suggest a buck boost transformer at the far end to correct the voltage. And if you have two refrigerators, then I would consider putting in a small panel with #4 conductors.
 
mwm1752 said:
Voltage drop = 2 x lenght x amperage needed(20 amps in this case & circuit size) x K (12 for CU & 21 for AL is common) / circular mills (Table 8 Chapter 9)
as rule of thumb never exceed 5% -- 120v x .05 = 6 volts 3% max is recommended - time to learn so I'll let you do the math. Hopefully your refrigerator does not require a dedicated 15 amp circuit -- another code section
Click to expand...

Thanks for that info. I have been trying to figure out how to hand calculate it.


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Strathead said:
Since the refrigerator is a relatively constant load, I would suggest a buck boost transformer at the far end to correct the voltage. And if you have two refrigerators, then I would consider putting in a small panel with #4 conductors.
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Buck boost transformers are not a good idea for correcting voltage drop. If you have desired voltage when circuit is loaded, you will have too high of voltage when there is little to no load. Running larger conductor often cost less anyway. Had the OP been running say 1500 feet, then maybe you are getting close to enough length the cost difference may be significant enough, but use step up then step down on each end not a buck/boost.

Kentuckian said:
The refrigerator will be on its own circuit.
FL A is 6A. Thanks for clearing it up that NEC recommends no more than 3% I was thinking it was 5%. So with 4ga wire and an fla rating at 6A. This should be fine on a 20a circuit?
Click to expand...

Voltage drop will be significantly less for 6A then the 16A most have been talking about.

But since you have two refrigerators you do have 12A if on one circuit. You still will have extra drop when compressor(s) is starting.
Multiwire circuit may be helpful here - if only one refrigerator is running - you have voltage drop for 6A @ 120 volts. If both are running you have voltage drop for 6 A @ 208 or 240 volts. (208 is a little more complex because of the 120 deg phase angle, but if you size conductors for the 6A @ 120V you will be fine.
 
Kentuckian said:
The refrigerator will be on its own circuit.
FL A is 6A. Thanks for clearing it up that NEC recommends no more than 3% I was thinking it was 5%. So with 4ga wire and an fla rating at 6A. This should be fine on a 20a circuit?
Click to expand...

The NEC doesn't require 3%, but it is more of a rule of thumb, however, some energy codes do require it. It is a recommended 3% drop on branch circuits and 2% on feeders (a total of 5%), but you are just working with branch circuits so that's why everyone is suggesting 3%.

Anyway - The amperage on the circuit directly affects the amount of voltage dropped so if you are only pulling 6 Amps per circuit @ 120V you will only need to run #8's to each circuit to get below the recommended 3% (this is based on copper not aluminum). You could put both refrigerators on one circuit since they only draw 6 amps. If you did this you would need to run #4's. I probably would stick with running two circuits, but that's just me. As mentioned above you could also run a sub-panel out there (could be useful for future circuits). There are multiple ways to skin a cat :cool:

-Drew
 
mwm1752 said:
Voltage drop = 2 x lenght x amperage needed(20 amps in this case & circuit size) x K (12 for CU & 21 for AL is common) / circular mills (Table 8 Chapter 9)
as rule of thumb never exceed 5% -- 120v x .05 = 6 volts 3% max is recommended - time to learn so I'll let you do the math. Hopefully your refrigerator does not require a dedicated 15 amp circuit -- another code section
Click to expand...

I was told that in the 2011 NEC voltage drop is now based on size of over current protection and not load. I cannot seem to find this is the code. Has any one else heard of this or is it one of those "old wives tales"?
 
Knightryder12 said:
I was told that in the 2011 NEC voltage drop is now based on size of over current protection and not load. I cannot seem to find this is the code. Has any one else heard of this or is it one of those "old wives tales"?
Click to expand...
I don't think that the NEC even addresses voltage drop other than to recommend that it be kept under 3% for branch circuits. It does not dictate how to calculate it in any section I could find.
 
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