Extension Cord Useage - Guage
Sometimes at home we need to connect to an extension cord - camper cord not long enough. What size guage should we be using? Does it matter ? Thank you
Forum Discussion
Hello. I have a 30 amp outlet and a 30 amp connection on the back of my rv. I’m almost 100’ away from the outlet. Is it safe to use a 100’ 30 amp plug on each end extension cord? Will I be able to use the ac and microwave at the same time? Or run the whole rv using this cord?
This thread is 3 years old. You might get more traction on your question if you created a new post.
ferndaleflyer wrote:
I keep mine powered up all the time with a 12ga cord plugged into a 20 amp plug at home. I have a 30ft 30 amp RV cord plugged into the 12ga 100ft cord. Have used this for years.
There is no one single answer to the problem, 100ft of 12Ga wire is perfectly acceptable if you are wanting to plug RV in and charge the battery, run some lights, turn fridge on..
However, add in A/C on top of all of above that and the voltage drop across that cord can cause enough voltage drop to harm the A/C and possibly other devices depending on your local starting voltage at the home outlet.
A quick check with a voltage drop calculator tells me that 100ft of 12Ga wire will drop 5.79% of the voltage at 20A draw..
Typically you want less than 3% drop..
So at your home outlet if the voltage was 120V, the end of that 100ft 12 ga extension cord with 20A draw you will have 113V, about 7V loss..
However, 1f the voltage at the home outlet was 115V the voltage at the end of the extension cord will now be 108V! Basically in the danger zone..
But keep in mind, you have wire between the home outlet and the main breaker panel to contend with and the 30ft 10 ga shore cord to RV cable all which added together make this drop even worse..
If one wanted to be able to run their A/C along with fridge, converter then it is in their best interest to upsize the extension cord to minimize the voltage drop.
Even 10 Ga at 100 ft is questionable at only 20A draw..
100 ft of 10 Ga with 20A draw, will have a loss of 3.46%, about 4V drop..
You actually have to go to 8 Ga to get drop below 3% for 100 ft..
You can check for yourself with a voltage drop calculator HERE just drop in your wire size and length..
With wire, you want to use the minimum length possible, if you don't need 100ft (say only need 50ft), use a shorter extension which I why I recommended using a couple of short 10 Ga RV extension cords..- I keep mine powered up all the time with a 12ga cord plugged into a 20 amp plug at home. I have a 30ft 30 amp RV cord plugged into the 12ga 100ft cord. Have used this for years.
- There are plenty of online wire gauge calculators. Most allow you to select the amount of voltage drop and to specify the length of wire and the maximum amperage you need.
I carry 2 extension cords, 25' and 100'. Both are 3 wire, 10 gauge. That is about the maximum you can get and they are already plenty bulky and heavy. The 25' extension allows me to pull a full 30 amps so I can run the A/C and something like the microwave at the same time. For the 100' extension the maximum draw is about 20 amps so I can only run one major appliance such as the A/C. - The size depends on two things. Current and length
For a 15 amp circuit I'd use at least 12ga Extension cord, Most big box home improvement will have 'em (Lowes, Home Depot, Mennards)
For anything bigger Get a cord at an RV store or make one custom
If making one custom "Up-Size" the wire.
8ga for 30 amp 6 for 50 IAMICHABOD wrote:
Following the recommendations here and my electrician I opted for a 10GA solid copper wire extension cord.
I would opt for a RV 30A 10 ga cord which has RV power connections on both ends..
This way you can take it camping with you just in case you run into a campground that doesn't have a 30A shore power connection close enough to your RV..
I have run into campsites that I have had to shift the RV between water, sewer and electric hookups just right for all three to connect.
With 10 ga wire, 25ft extensions are considerably easier to handle, 50ft might make you regret your decision.
If you own your home and need 50ft or more extension then consider having a RV shore power outlet put in near your RV parking and proper wire buried.. Makes life very easy and you don't have extension cord laying on the ground to trip over or catch with your mower deck..
On edit, fixed spall chalk error..- Following the recommendations here and my electrician I opted for a 10GA solid copper wire extension cord.
You don't want solid wire (not sure they even sell them). You want "stranded" copper wire. Romex in houses is solid wire (ie: 1 strand). In a house, it's OK because once installed, it rarely if ever is moved. An extension cord is constantly being bent and unbent. The outer layer of a very thick strand is stressed more than the outer layer of a thin strand. Eventually, that outer layer "work hardens" and becomes brittle and can break or worse, the poor connection around the break point can overheat. The thinner strands of stranded wire experience less strain so they hold up longer.
Of course, it really depends on how long the wiring run is and how many amps you are drawing. If you are just running the fridge and a few lights (maybe 3-5amps), a little 15amp cord from home depot is generally going to be fine. Once you want to run the air/con and everything else (15-24amps), even 10ga may be marginal if you have the standard 50ft cord with a 100ft extension.
Regardless, it's a good idea to keep a voltage meter plugged in where you can see it or have a surge protector that also checks for low voltage and will cut power if it gets too low. We have a meter that stays plugged in near the door and if we see it get down around 108v or lower, we shut down and switch to generator power.
- Right now we are parked forward in a back in site because of the view. Just one reason why we carry a RV extension cord.
- #12 is fine up to 100' unless using the A/C.... then you need to check voltage in the RV stays above 108 when running.
- Are you just running the frig on electric and a few lights getting ready for a trip? Then a 14 ga 50' will be just fine.
Now if you want to run the AC also you'll need a 12ga cord. I have had no issues using a 12ga 50' cord. AC only draws 12-13 amps so a 20A rated cord is fine.
