# Gauge of wire for 15 A extension cord

Discussion in 'Electrical and Wiring' started by swimmer_spe, May 19, 2017.

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1. May 19, 2017

### swimmer_spe

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I want to get a 15A extension cord that will reach about 25 feet. I do not want to loose amperage over the length of cable. What gauge of wire do I need?

2. May 19, 2017

### nealtw

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You are plugging into 14 gauge but you can buy extension cords with 12.

3. May 19, 2017

### swimmer_spe

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I know you loose either amperage or voltage over a wire, and I am trying to avoid that.

4. May 19, 2017

### kok328

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voltage drop will not occur under 100 feet, so your ok to use 14AWG cord.

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5. May 19, 2017

### bud16415

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There is a voltage drop whenever there is resistance. Resistance is based on the circular area of the conductor, the material in the conductor and the length of the conductor.

There are dozens of calculators on line you can use. Here is the first one that came up.

http://www.electrician2.com/calculators/vd_calculator_initial.html

There will always be some drop no matter how short your cord is. But at some point it becomes significant.
For example: copper wire

#14 / 120v / 15a / 100’ = 9.4v drop
#12 / 120v / 15a / 100’ = 5.9v drop
#10 / 120v / 15a / 100’ = 3.7v drop

#14 / 120v / 15a / 50’ = 4.7v drop
#12 / 120v / 15a / 50’ = 3.0v drop
#10 / 120v / 15a / 50’ = 1.9v drop

Practically speaking a #12 is about twice the price as a #14 so you have the facts to decide what suits your needs best.

On a side note many years ago I was at a garage sale and an old guy had a homemade cord that was 200’ made out of heavy rubber coated wire #10 with a 4x4 box on the end. It weighs a ton. I asked him what he wanted for it and he said five bucks if you are going to use it and not sell it for scrap. I said I would use it quite a bit. He had it for many years and got the cable for free someplace and he wanted it to go to a good home. I’m not done with it yet but when I give up on bigger projects I figure I will sell it for 5 bucks also to the right person that comes along. I have loaned it out a dozen times and have thought about making a dolly to tote it around and wind it up on. Thing about tools is you only have to buy them once most of the time.

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6. May 19, 2017

### nealtw

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I had a cord like that, we were using it on the roof of a church, wired into the breaker box, 20 ft up should be safe. They cut it where it came thru the wall, they must of brought a ladder.

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7. May 19, 2017

### swimmer_spe

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So, 12 or 10 gauge it is...

8. May 19, 2017

### bud16415

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Assuming you are going to power your whole garage thru this cord as you mentioned in another thread I would get a 50’ #12.

I doubt you will be drawing 15a very often but with lights and maybe an air compressor I could see you hitting 8-10a.

9. May 20, 2017

### nealtw

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It is temp until he wire the garage.

10. May 21, 2017

### swimmer_spe

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That is correct, it will be temporary power for my garage.

I plan to run a couple of lights and possibly a power tool/compressor off of it, if possible. As far as I know, the outdoor plug is on it's own circuit.

11. May 22, 2017

### afjes_2016

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If you are going to plug the extension cord into an outside receptacle do you know if it is GFCI protected?

If it is then fine. If not either put in a GFCI receptacle or use one of these (plug-in GFCI adapter) for your own personal safety. Plug it into the outside receptacle and then plug the extension cord into it. There are many on the market just find one that is good quality; spend a few dollars more for better personal safety.

12. May 22, 2017

### swimmer_spe

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It is a GFCI plug

13. May 23, 2017

### nealtw

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The compresser may give you trouble on a gfci

14. May 23, 2017

### swimmer_spe

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It didn't while building the walls of my garage.

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