Can a 15-amp + 30-amp to 50-amp adapter work?

The answer is simple but maybe not obvious...

Mike,

I hope you are well. We met you at the Hershey RV show this year and I had a question as we are getting ready to pick up our new RV next week. Was looking to get this adapter and was wondering if I would cause problems with my 50 AMP RV if I used this? And if it is ok, would this give you 45 amps of power? Also, if the park only had 30 amp hooks ups could I use this as just a 30 AMP connection as well? Or is there a more appropriate way to connect a 50 AMP RV to a 30 AMP box? Thanks for any insight you have. - Jon V

Dear Jon,

This same question pops up periodicalaly, so I’ve already done the basic research. But in the interest of fully explaining how it works (or doesn’t work), I’ve already ordered the exact Y-Cable you linked to in your email. It will arrive next week and I’ll do a video demonstration soon.

What’s the basics?

These are typically called 45-amp Y-adapters because 30-amps plus 15-amps equals 45-amps. The idea is that you can pull 30-amps from the TT-30 outlet on the pedestal, and an additional 15-amps from the 20-amp outlet (Yes, it’s actually a 15-amp plug in a 20-amp outlet, but that’s another story).

Here’s the problem…

While it seems like this should work, the problem is that EVERY 15 or 20-amp exterior outlet is required to have GFCI protection. And that GFCI functions by comparing the outgoing load current on the live conductor, with the returning current on the neutral conductor.

Because the 50-amp shore power cord on the RV utilizes the same neutral conductor for both Hot-1 and Hot-2, the neutral return current will (nearly) always be different than the outgoing load current on either hot conductor.

What happens…

Because the GFCI outlet on the pedestal is looking for any load current imbalance exceeding 5mA, this 45-amp Y-cable won’t work with a properly wired pedestal or home exterior outlet. Read my full article on GFCI troubleshooting HERE.

And while this 45-amp Y-adapter could work in a non-GFCI 15 or 20-amp outlet, you NEVER want to defeat a GFCI since that removes one more layer of shock prevention and could open you up to electrocution danger and potentil liability if you tamper with a live pedestal in a campground. So DON’T do it.

A 30 to 50-amp adapter will work (but limited to 30-amps total current)

More on this in my upcoming video, but your only possible solution when plugging a 50-amp RV into a 30-amp pedestal outlet is to use a properly wired 30/50-amp adapter like this one. It provides 120-volts to both 50-amp circuits in your RV, but with a maximum of 30-amps combined current.

Watch for my video demonstration next week

Standby for a visual demo of why GFCIs trip next week. It will all make sense after you see exactly what a GFCI is doing to protect you from shock. See you then.

Let’s play safe out there… Mike