I was reading an article you wrote about 30A pedestals. I’ve just purchased a piece of land and there’s a new 30A RV outlet. The problem is that the plug is 90 feet away from my RV parking. I’m trying to keep it near the connection to the septic system. The RV is a 30A travel trailer with a 25-foot power connection.
I’m trying to determine if I can make up a 8/3 or 6/3 flexible extension cord to service the trailer that I can spool up after using on the weekends. I’d prefer not to use Romex because it’s so rigid. I’d really appreciate any thoughts you may have on best options. —Patrick Nolan
I would recommend you get or make a 100-foot 8/3 flexible extension cord using SOOW rubberized jacket cable. (See below.)
SOOW is hard-service flexible cord rated for up to 600 volts. It has a much thicker jacket wall than the lighter-weight SJOOW Junior Service flexible cord, which is only rated for 300 volts. You can see that it uses stranded wire which is rated for flexing, so it can lay on the ground and be wrapped up easily. The latest electrical code specifically calls for SOOW cord for any cable runs on the ground that can be stepped on or run over.
As for wire gauge, while in theory you could get away with 10-gauge cable rated for 30 amps, because of the length of the run you’ll reduce voltage drop significantly if you go one size heavier and use 8-gauge wire, especially if you’ll be running the air conditioner. I think it would also be best if you can get a premade cord with molded ends that are waterproof. However, I just did a quick search for such a cord but don’t see 100-foot RV extension cords in stock, so you’ll probably have to have one custom made. You can expect to pay around $200+ for this sort of thing. See below for a wire gauge chart that shows relative size of the wire with the maximum amperage it’s rated for:
Under no circumstances should you ever use Romex cable for an RV extension run on the ground. (See below.)
That’s because it has solid conductors that can’t take much flexing without breaking. Plus the outer vinyl jacket won’t stand up to foot traffic or other abrasion without breaking through. Additionally, any extension cord plug you put on the end of it won’t be rated for solid wire, and will likely loosen up over time and cause a fire. But you could use direct-burial Romex buried underground and put waterproof boxes on each end, which would extend into short SOOW cords that plug into the power outlets. That would be code compliant and safe.
A good extension cord that’s properly cared for will last you many years, while a cheap extension cord can fail and possibly expose your RV (and maybe you) to electrical damage. So this isn’t something to go cheap on.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.