Not all outlets and adapters are created equal. Here’s what works…
Hi Mike,
I subscribe to your newsletter and do not believe I have seen this before though I could be wrong. This is a dryer plug you plug into your dryer outlet and then can hook up to your RV with the 30 amp RV plug in end. My dryer is 240 volts thus if I used this, I would fry everything in my RV correct? There is nothing that limits it to 110-120 volts is there?
Thank you - Jim
Hey Jim,
Let’s take a closer look at this plug and consider how it works.
This adapter is designed to plug into a 4-wire NEMA 14-30R dryer outlet, which is a modern version of the old 3-wire dryer outlet. And unlike a 3-wire 240-volt outlet it includes a neutral conductor which is wired like this.
That’s good because it does have two 120-volt legs and a neutral plus a ground. That’s what allows the 240-volts to be split into 2 legs of 120-volt each for all the 120-volt appliances in your RV, and most of them in your bricks and sticks house.
What does your 30-amp RV need?
Here’s what a 30-amp shore power cord needs to plug into. As you can see, it needs one hot, a neutral and a ground. That is what provides the 120 volts needed by your 30-amp RV.
Will this adapter work?
However, the adapter you’ve selected doesn’t have the right kind of outlet for your 30-amp RV. Both are wired for a 2-pole / 240 volt service with 2 hots, a neutral and a ground. The NEMA 14-50R outlet will power a 50-amp RV properly up to 30-amps of current. But neither outlet will connect to your 30-amp RV shore power cord and provide the 120-volts needed on 3 wires.
All is not lost… here’s something that works!
As you can see, this dogbone adapter shown below connects to the 30-amp, 4-wire dryer outlet, and converts it to a 3-wire TT-30 RV connector. And because it uses just one of the hot legs from the 240-volt split-phase service, it converts the 240-volts from the 4-wire dryer outlet into the 120-volts needed for the 3-wire TT-30 RV plug. You can buy this dogbone adapter from Amazon HERE.
Let’s play safe out there… Mike
I tried to order the last one but it was no longer available
Try this:
https://amzn.to/44sIRoU
That worked. Thanks
It appeared to me the first split pigtail adapter would be used to retain a receptacle to keep the drier connected when needed and to plug in a 50-amp RV or EV at the same time. But again, drawing too much electric power by using an electric drier and having a high electrical load from a 50 AMP RV or EV charger would likely overload the circuit and trip the 30 AMP circuit breaker in the panel board protecting the wiring. I imagine these pigtail adapters are not meant to be used as permanent connections as we typically would not find both 14-50R and 14-30P receptacles hardwired on the same 30 AMP circuit in a home.
Mike
Not questioning your answer but I would change or clarify one word. The 50 amp to 30 amp adapter doesn’t ‘convert’ 240 vac to 120vac. I think it only uses one of the hot (120 vac) legs. Correct? Just thought this might be confusing to the OP.
That’s true, but what would be a better way to say it in layman’s terms.
Good question. Just thought ‘convert’ makes it sound like it changes the voltage. I thought saying it only uses one hot leg would make sense but one has to have a basic understanding of electricity to have any of this make sense. Thanks for the reply.
I work with engineers from Europe all the time, any even they get confused with split-phase service in the US.
👍
Now for more confusion and fun, let’s discuss the “reverse” plug of what’s discussed here… instead of 240P to 120Rx2 here, there *IS* a 3wire 120P to 4wire 240R. I intentionally bought one, and yes it should be impossible as described. It’s actually a cheat on the split phase 120, putting the same phase on both phases of the “240” plug… why? I use it to run my very low demand 240v house from my ultra-quiet 4kw/120v RV generator. No, 240V loads don’t work (they would see 0 volts if they were transferred onto genny) but everything 120v works. If I plug in my bigger/louder 12kw 240v genny, then the same 4wire genny input seamlessly works for that too. Its rare I NEED clothes dryer or hottub while power is out anyway, and 4KW is generous for the rest of house. Most 50A RVs don’t actually use 240v either, so i think it’s a similar dogbone as you’d use for running 50A RVs on smaller gennies.
A lot of people think the old 3 wire hookups are 2 hots and a ground but I disagree, they are 2 hots and a neutral. If it were 2 hots and a ground it would be 240 only, not 240/120. 3 wire hookups always required all 3 wires to be insulated, or the use of SE cable where the outer layer is approved to carry neutral current. The neutral is bonded to the cabinet to act as a grounding means.
It is actually a sanctioned bootleg ground. If the neutral conductor opens up, then the chassis of the dryer could be energized with 120 volts.