Community Forums

Ter Uh P · 03-11-2022, 06:53 PM

AC service panel had a 50 amp 4 wire receptacle wired with 2 hots, a neutral and a ground on 2 pole 50 amp breaker. I didn’t have enough 50 amp power cord to reach the receptacle. I have a 50’ 30 amp 3 pole cord, 2 hots and a ground. So I replaced the 50 amp breaker with 30 amp and replaced the receptacle to a 30 amp. Plugged the 30 amp cord into receptacle, connected a 30 amp 3 prong to 50 amp 4 prong adapter and then plugged the rv 50 amp cord into the other end of the adapter. Turned on the 30 amp breaker and the spider panel inside the coach says reverse polarity and there is no AC voltage shown on either leg on the spyder panel.

I unplugged the power cords from the receptacle and will check all connection in the morning.

How can you have reverse polarity in AC power?

bigb56 · 03-11-2022, 06:57 PM

So you used a 30 amp 2 pole breaker and a 3 wire cord? You can't run "2 hots and a ground" to your RV, you need a neutral and 3 wires will only give you one leg of power, not two. The adapter is going to take the one hot leg and bridge it together into your 4 wire and if you wired it with two hots it will put the other hot leg to your RV's neutral. (because the other side of the 30 amp is supposed to be neutral so the adapter routes it to your neutral in the 4 wire)

twinboat · 03-11-2022, 07:30 PM

30 amp is strictly 120 volts, one hot, one neutral and one ground.

Your confusing your polarity tester doing what your doing.

Old-Biscuit · 03-11-2022, 08:10 PM

DID you wire that 30A with 2 hots...TWO 30A Circuit Breakers each feeding Hot (like the 50A CBs were)???

If YES you connected 240VAC to your RV

30A is 1 hot, 1 neutral, 1 ground using 1 CB
*if that is how you wired it then you have Hot & Neutral reversed at the 30A Outlet

chuckftboy · 03-11-2022, 08:44 PM

There is a difference between a 30-amp 125 volt receptacle and a 30-amp 250 volt receptacle. A RV 30 amp is 120 volts, a 30 amp residential dryer is 240 volts. If you are trying to get 30 amps 240 to the RV you'll need a different cord with 4 wires.

Ranger Smith · 03-12-2022, 03:39 AM

No Offense sir but . . . You should hire an electrician as it seems you do NOT know what you are doing and will probably fry everything in your rv that runs off of AC power

Shadow5501 · 03-12-2022, 06:30 AM

Quote:

Originally Posted by Ranger Smith

No Offense sir but . . . You should hire an electrician as it seems you do NOT know what you are doing and will probably fry everything in your rv that runs off of AC power

This times ten. If you have a Progessive Industries EMS or similar, it has protected your RV from damage. If not, you’ve connected it to 240 volts and fried everything. Get an electrician to install the outlet, your understanding of wiring is not sufficient to perform this work.

Old Scout · 03-12-2022, 06:36 AM

You are so fortunate you had a power monitor system to protect your RV--classic attempt to hook up RV to a "drier plug"--240 volts!

bigb56 · 03-12-2022, 08:21 AM

See picture which shows how if you wired the 30 amp receptacle with 2 hots you now have one of them going to your neutral in the RV due to the design of the adapter you used which is designed with the assumption that it will be plugged into a 120 volt receptacle.
If you did only run 1 hot and 1 neutral to the 30 amp then you got the hot and neutral reversed, the 30 amp TT receptacle has a silver terminal indicating where the neutral goes..
I'm assuming you improperly wired it with 2 hots due to your comments "2 hots and a ground" and "How can you have reverse polarity in AC power?"
It's true there is no polarity on line to line AC power but there is polarity on line to neutral/ground, which is how a 30 amp RV receptacle is wired.

Persistent · 03-12-2022, 10:16 AM

Good advice above! Put it all back the way it was. At least get it inspected before powering it up.

A 30 amp 120 volt outlet can be added next to the 50 amp 240 volt outlet. It requires a sub-panel with a 30 amp single pole breaker in it to protect and control the 30 amp outlet. Existing 50 amp 240 volt branch wiring, branch circuit breaker, and outlet can remain in place.

The 30 amp outlet hot would be connected through the 30 amp breaker to one hot leg of the 50 amp circuit. The 30 amp neutral and the 30 amp ground get connected to the 50 amp counter parts.

There are sub-panel boxes designed specially for RV hook ups like this. They often include a 20 amp outlet as well. You see them often in RV parks.

Use a commercially available "dog-bone" connector to connect 50 amp plug to 30 amp extension cord.

It would be cheaper and easier to get a 50 amp 240 volt extension cord than to do all this.

I recommend you get a licensed electrician to do the work.

RRR · 03-12-2022, 10:45 AM

Jim_HiTek · 03-12-2022, 10:53 AM

Quote:

Originally Posted by Shadow5501

Snip: Get an electrician to install the outlet, your understanding of wiring is not sufficient to perform this work.

Don't really want to just hire any old electrician because few of them know about RVs and often wire them up like a stove where there are 2 hots and one ground. Frying the RV which only uses 1 hot, 1 grnd, and 1 neu.

Best to contact a mobile RV tech and ASK them if they have the knowledge of 30 amp wiring in an RV.

Ray,IN · 03-12-2022, 12:49 PM

This website explains RV input power wiring in detail. Whoever you hire to do the wiring, show them this website first.
A 30A RV cord has only one hot wire, as shown previously.

Ter Uh P · 03-13-2022, 10:06 AM

I rewired the receptacle as instructed above and all works well. Thanks for the help.

End result was I thought the 3 prong plug was 220 and not 110 VAC.

All good!