Extension Cord Useage - Guage

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..