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Old 09-30-2016, 04:32 PM   #1
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Default What a difference a gauge makes

Back in 2008 when I got my 5th wheel trailer home I decided it would be best to store it with “yard power” applied to keep the batteries topped off and the fridge powered up. (and that's all, mostly) I purchased a 100 ft., 14 gauge extension cord and made my own adapter to fit between the trailer and the female 15 amp outlet on the cord. This is plugged into a standard household 15 amp outlet on the side of the house.

After eight years of UV light, rain, mold, dirt, corrosion and having been run over once with a lawn mower, this past week I replaced all that with a new 12 gauge extension cord (that weighs a whopping 15 pounds) and a fancy store bought adapter that features a positive mechanical and water tight connection to the trailer that my home made adapter was lacking.

https://www.campingworld.com/shoppin...mart-led/69586

The extension cord I got at Harbor Freight, list $70 but I had the 20% off coupon and got the free with purchase stuff, too.

Then the test engineer in me thought I’d see if the expense was worth it.
A few definitions for our test: Minimal Load = The 12 converter is running, with the fridge, a Vortex fan and 1 LED light fixture. A/C on = All of that and of course the 13.5 ducted air conditioner is running. Measurements were taken at an outlet inside the trailer.

14 gauge
Minimal Load = 121 volts
A/C on = 108 volts

12 gauge
Minimal Load = 121 volts
A/C on = 113 volts

So I got back 5 volts of drop with the new, heaver cable (with non-corroded connections). Don’t seem like much, and I might not want to camp out there like that, but I sure feel better about running the A/C while I’m out there working/cleaning/stocking up. As long as I don’t use the toaster and the A/C at the same time….
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Old 09-30-2016, 05:11 PM   #2
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Heavier gauge, more wires, the little electrons aren't fighting one another as much to get to the other end.
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Old 09-30-2016, 06:40 PM   #3
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You are right at the max.
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Old 09-30-2016, 08:02 PM   #4
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You are right at the max.
You mean the maximum minimum?
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Old 10-01-2016, 06:03 PM   #5
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He means the max current on a 15A breaker. You're right there with a 13,500 BTU/hr A/C unit.

You gained back 5v of drop. At 15 amperes, that's 75 watts of power that used to be wasted making that cable nice and warm. Actually, you got back a little more than that, because, when the voltage is too low, most motors (other than series-wound motors) will draw increased current. You've got two motors in the A/C. Without knowing for sure, I'd guess the compressor has a capacitor-start induction-run compound motor and the fan has a self-starting induction motor. Each motor will draw increased current (and run slower and hotter!) when the voltage is low. Sometimes they'll run so hot they melt, which is expensive. But 108v wouldn't be low enough to kill them that way.

I'd measure, also, at the outlet where you plug in the extension cord at the house. If you're dropping 8v (121-113=8), that's still a lot.
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Old 10-02-2016, 10:08 AM   #6
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At 100 feet you would be much better off with a #10 wire or greater. The voltage drop increases current a typical motor will draw 220% greater current just to start add a high head pressure on the AC unit and you are up to the max. The voltage drop at start up load is probably a good bit greater than just 5 volts.
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Old 10-02-2016, 10:47 AM   #7
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At 100 feet you would be much better off with a #10 wire or greater. The voltage drop increases current a typical motor will draw 220% greater current just to start add a high head pressure on the AC unit and you are up to the max. The voltage drop at start up load is probably a good bit greater than just 5 volts.
Most certainly agree with all of that. I'd use #6.
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Old 10-02-2016, 12:18 PM   #8
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He means the max current on a 15A breaker. You're right there with a 13,500 BTU/hr A/C unit.
Oh yeah. All I ever run is the converter and the A/C. Or the converter and a space heater, which draws less than the A/C. That's why I said you can't camp like that, not able to run the toaster without turning off the A/C. But even with the smaller cord, I never tripped the breaker, except for running over it with the mower.

As for heavier gauge wire it's just not in the budget.

Someday off in the future I hope to make a real parking pad for the trailer. When I do it will have a pedestal like in a campground and water, too.

Someday.
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Old 10-02-2016, 01:13 PM   #9
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Why I carry 100' of 12ga, Also 10 and 20 feet lengths.
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Old 10-02-2016, 07:50 PM   #10
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The problem is not so much tripping the breaker as it is setting the wire on fire or damaging electrical stuff with low voltage. Good camp ground wire runs are reasonably short the pedestal’s are generally a #8 wire feed.
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Old 10-03-2016, 11:00 AM   #11
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You might be surprised to find out how much current a wire can safely carry if it's just lying on the ground instead of burried in a wall... I Know I was

There are 3 ratings for any given size/type of wire.. Free air, In a wall/Conduit, and coiled.
A wire that overheats at 5 amps coiled, can easily carry 20 in a wall and much more in free air.
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Old 10-03-2016, 05:49 PM   #12
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A wire that overheats at 5 amps coiled, can easily carry 20 in a wall and much more in free air.
Makes you wonder what role induction plays in that.
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Old 10-03-2016, 06:26 PM   #13
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Makes you wonder what role induction plays in that.
Induction plays no role at all. Coiled wires merely concentrate the generated heat. Coiled twice around, twice the heat in the same volume. Coiled ten times, ten times the heat in the same volume.
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Old 10-03-2016, 07:20 PM   #14
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I think you will find that fee air means just that, air 360* even laying on the ground will effect over all current. Wires in a wall effect each other in say Romex. In conduit it's even worse.
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Old 10-05-2016, 12:25 PM   #15
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I agree N3LYT, even lying on the ground will affect it.. However,,,, How much more so buried in a wall?
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Old 10-07-2016, 07:49 PM   #16
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It's what they are housed in not really the wall. Romex wire covering traps heat to some extent is it enough to cause a problem? Probably not because the power demand is not there in a normal household so a #12 is suitable for 20 amps and a #14 is fine for 15. When you start bundling numerous current carrying wires in conduit then it becomes a problem. A good example is service drops the 2/0 power co over head wire will stand 700 amps (so I'm told never tested it!) but once it is connected to the house sheathed 200 amp wire must be 4/0 or even open wire in conduit.
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Old 10-08-2016, 07:37 AM   #17
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I agree N3LYT, even lying on the ground will affect it.. However,,,, How much more so buried in a wall?
What if the ground is cold?

Oh, but then I probably wouldn't need the air conditioner, would I.
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Old 10-08-2016, 10:17 AM   #18
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Yeah I guess you could put it in a bucket of cold water..
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