Dual 30-amp to 50-amp Y-adapters

Are they safe and do they work? (Updated with Polarity Testing)

Dear Mike,

I have seen people using the 50 amp power cord on their coach to plug into a pair of 30-amp outlets. They plug their RV into a 50-amp Y-adapter which spits into two 30-amp male ends and then plug each end into a separate 30-amp outlet . They do this because there isn't a 50-amp outlet on the pedestal, but there are two separate 30-amp outlets. Is this safe to do for two weeks? -Tom

Hey Tom,

This is a possible solution as long as you understand the limitations.

Yes, this works if the pedestals are wired correctly

Note that this type of adapter has a pair of 30-amp male plugs feeding a single 50-amp female outlet. However, there’s two different ways the 30-amp outlets can be wired on the pedestal(s) than can affect operation.

If the two 30-amp outlets are wired on opposite Legs of the split-phase 120/240-volt service, (One on L1 and the other on L2), then the neutral currents in your shore power cord will be subtractive so the amperage will never exceed 30-amps. This is exactly how a properly wired 50-amp outlet is supposed to work, except you’ll only have a combined current of 60-amps available instead of the 100-amps in the standard 120/240-volt NEMA 14-50 pedestal outlet.

But if both of the 30-amp pedestal outlets are wired on the same split-phase Leg (L1+L1 or L2+L2), then the neutral currents will be additive, so it’s possible that the neutral conductor in your shore power cord would reach 60 amps. While technically a code violation since that neutral is only rated for 50 amps, unless you’re pulling 30-amps continuously from both sides of your RV power it should be safe. So if you do use one of these adapters you’ll want to keep a watch on any signs of overheating on the 50-amp shore power plug.

When it doesn’t work and makes fireworks

But, if one of the 30-amp receptacles is accidentally wired with Reverse Hot-Neutral Polarity, then plugging in a 30/30/50-Amp Y-Adapter will create a hot-to neutral short circuit. At the very least, you’ll trip circuit breakers. But you might create an arc-flash which can melt the contacts and possibly blind you if you’re not wearing eye protection.

See the video below which shows how to check for correct TT-30 Polarity before plugging in a 30/30/50-Amp Y-Adapter cable.

No, 45-amp Y adapters won’t work with a GFCI outlet

These so-called 45-amp Y-adapters that are designed to plug into one 30-amp and one 20-amp pedestal outlet just won’t work. That’s because all 20-amp outlets on pedestals are required to have GFCI protection. And because the neutral currents between the two outlets are intermingled, the GFCI 20-amp outlet will instantly trip with any load current over 5mA (that’s 0.005 amperes of load current). So don’t waste your money, because they can’t work with a GFCI outlet.

Just because you can buy something on Amazon of eBay doesn’t mean it’s safe or works.

Let’s play safe out there - Mike