My trailer came with, what I believe to be, a 25-foot 30-amp power cord that connects to trailer with a round connector with locking ring... fairly standard for trailers from what I've seen. My question comes to the use of an extension cord with this cable. I've looked at extension cords that are 50-feet long, as there is a camping space where I know it will be around 75-feet or so away from the nearest I can park my trailer. I've looked up charts listing appropriate gauge wire for different length runs at single-leg standard voltage. For up to 50-feet, it recommends 10-gauge wire. For 75-feet, it recommends 8-gauge wire. For 100-feet, it recommends 6-gauge. My assumption is that the power cord for the trailer is 10-gauge. 50-foot RV extension cables are also 10-gauge. This jives with the chart I looked up... BUT... I'm plugging 25-feet into 50-feet, a total of 75-feet. At 75-feet, the recommendation is 8-gauge. I have not seen an 8-gauge, 50-foot extension, nor would it take into consideration the 25-feet of 10-gauge for the main trailer. Am I just over-thinking this? Is it an issue?

10 gauge should be fine, I run 60' of it running air con and it's fine. From what I see on Amazon, if you want to go 8 or 6 gauge, you'd need a 50a extension.

"My assumption is that the power cord for the trailer is 10-gauge. 50-foot RV extension cables are also 10-gauge. This jives with the chart I looked up... BUT"STOP assuming. Instead, LOOK at the cable. The wire gauge is printed on the cable insulation. (at least it was when it was new) There's your answer. If the printing/embossing is no longer visible, pull the cover off the j-box where the cable connects just inside the RV. Look at the wire. "Am I just over-thinking this?"No. IMO, You aren't thinking at all. You are reacting.Chum lee

10 AWG is fine for 75 line feet. Yes you will have some voltage drop. It should be within operating specs of most of your gear. Www.calculator.net has a voltage drop calculator based on wire gage, wire length and amperage use. It's pretty accurate. No AC & microwave at the same time! 120vac pulling 30 amps through 75' of 10AWG drops voltage to 115.4vac IIRC from the other page.

Boomerweps wrote:No AC & microwave at the same time!x2, and no water heater. Even at 30' I'll melt plugs doing that.If I need a/c and MW, like for dinner on a hot day, I'll use my inverter! Yep.

Yes, it can be an issue. If you need the full length, then limit the load to less amperage so that there is less voltage drop. Sometimes you might be in a campground where the voltage is already low and you can't afford any loss. Get a voltmeter that displays all the time so that you can see at a glance what is going on. Running a motor driven appliance like the A/C can result in damage if the voltage is too low.

Gauge of extension cord | Good Sam Community

cavie
Explorer
May 18, 2019
Just put the WH on gas and you'll be good to go.
opnspaces
Navigator II
May 18, 2019
I would have no problem running a 50' 10g extension cord with no AC. I wouldn't be surprised if you could run the AC with it. Buy the 10g cord and go have fun. if it's so hot that you need the AC, have someone turn it on while you watch the meter to see how low the voltage drops.
wa8yxm
Explorer III
May 17, 2019
Most folks do not know this but there are multiple ways to figure the gauge needed.

10ga in a wall, ,V/s 10ga lying on the ground.. HEAT is an issue. lying out on teh ground gets rid of heat much faster so can can haul more current.

VOltage drop Many parks are a tad anemic already so you do not need more voltage drop.. So if you can.. Go big.
pianotuna
Nomad III
May 17, 2019
2oldman,

Since I started using the autoformer I've not had a single melted plug.
cavie
Explorer
May 17, 2019
Order a 50 ft. 30 amp RV extension cord and you will be just fine. The cord is in free air and not in conduit or berried in the ground. You will be able to run the A/C if you are using an EMS. It will shut you off for low voltage. Install hard start capacitor on your A/C. They cost about $15.00 on Amazon. Run tour WH on gas when using the long extension.
SoundGuy
Explorer
May 17, 2019
RonRN18 wrote:
I have installed a Progressive Industries EMS-HW30C in my trailer, so I do get a display of the voltage coming in, as well as the amperage being used (it also displays the frequency of the AC and an error code if something is wrong with the power, but that isn't at issue in this regard).

So because your EMS is a hard wire installed at the trailer end of the incoming main service cable you're seeing incoming source voltage under load, including any voltage loss in the cable. As long as that displayed voltage remains above your PI disconnect threshold voltage of 104 vac you're good to go. Using anything heavier than 10 gauge for your 30 amp rig is nonsense, just keep an eye on your EMS's remote monitor and adjust what you have powered at any given time if you're seeing the voltage get too close to that 104 vac threshold.
RoyB
Explorer II
May 17, 2019
I picked up a couple of 50-foot contractor grade YELLOW COLOR extension cords from a yard sale.. These are 10 gauge with heavy covering...

Those are what I use with my POPUP 30A setup..

Those red-orange cords you find at WALMART are not heavy duty enough...

You probably could pick a couple of USED RV30A Extension cords from local RV Dealer that has the RV30A connectors on them. They run power to all of their RV units on display... I know when I purchased my RV it had one connected up and I asked for it and got it laying inside my doorway haha... It was a 50-foot one...

I have this one run from the garage 120V-20AMP circuit to mate up with the pull-out 30A cord on my popup in the driveway or in the back yard...

Roy Ken
RonRN18
Explorer
May 17, 2019
The reason I said I assume the power cord that came with my trailer is a 25-foot cable with 10-gauge wire inside is because my trailer is parked at a storage yard as I'm doing my research, but research shows that 25-foot, 10-gauge is fairly standard.

I have installed a Progressive Industries EMS-HW30C in my trailer, so I do get a display of the voltage coming in, as well as the amperage being used (it also displays the frequency of the AC and an error code if something is wrong with the power, but that isn't at issue in this regard).

I just had some concerns before spending the money for an extension cord. Where I plan on using the extension cord, I don't think I'll need the air conditioner there... I'll be in the shade and it rarely gets above 90 degrees. I might want to use the microwave though. Primarily, I'll just be using DC power for lights and my MaxxAir fan, and AC for battery charger, refrigerator and possibly water heater. The refrigerator can automatically switch between AC and gas while the water heater I have a switch for electricity and a switch for gas.
SoundGuy
Explorer
May 17, 2019
RonRN18 wrote:
My trailer came with, what I believe to be, a 25-foot 30-amp power cord that connects to trailer with a round connector with locking ring... fairly standard for trailers from what I've seen. My question comes to the use of an extension cord with this cable. I've looked at extension cords that are 50-feet long, as there is a camping space where I know it will be around 75-feet or so away from the nearest I can park my trailer. I've looked up charts listing appropriate gauge wire for different length runs at single-leg standard voltage. For up to 50-feet, it recommends 10-gauge wire. For 75-feet, it recommends 8-gauge wire. For 100-feet, it recommends 6-gauge. My assumption is that the power cord for the trailer is 10-gauge. 50-foot RV extension cables are also 10-gauge. This jives with the chart I looked up... BUT... I'm plugging 25-feet into 50-feet, a total of 75-feet. At 75-feet, the recommendation is 8-gauge. I have not seen an 8-gauge, 50-foot extension, nor would it take into consideration the 25-feet of 10-gauge for the main trailer. Am I just over-thinking this? Is it an issue?

Yes, you're overthinking this. It's all about unloaded source voltage (which should be 120 vac here in N America), how long the run is, the cable gauge, and the total load you're putting on that cable. Just plug the numbers into this Voltage Drop Calculator and you'll know what to expect. Here in Ontario runs of 100' and more aren't uncommon at all, I carry as much as 140' of 10 gauge and in fact have had to use it. It's just a matter of monitoring how much you're drawing from the source supply. No way would I ever carry anything heavier than 10 gauge, I'll lower my expectations as to what I can power at the same time before I'll drag a heavy 8 gauge or 6 gauge cable around.
beemerphile1
Explorer
May 17, 2019
Are you planning to run at 30a continuously? If so 8g is needed. What do you plan to be operating and what percentage of the time?

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