50 amp wiring question

[dryfly]

I'm getting a new trailer and it will be my first with 50 amp service. I've always noticed the standard NEMA 14-50R 4 pole receptacle on the AC pedestals but never paid any attention to the female shore power receptacles on the trailers. I'm guessing they are a NEMA SS2-50P 4 pole??

Apparently there is no concern in balancing the loads on the 2 legs in the breaker panel when using a trailer wired with a 50 amp service on a 30 amp supply (using a 30 to 50 adapter)? Looks as though the 2 120 volt legs of the 50 amp supply are combined into one leg in the adapter.

[CA_Traveler]

I prefer to use the heavier 50A cord with a short adapter as there is less voltage drop and it's almost always the 30A plugs that have lower voltage and the 30A extension cord adds to that.

What you want to do is also a reasonable solution.

[CA_Traveler]

Dutch,

Doesn't your portable unit display a error code? My PI HW50C has 11 codes.

[dryfly]

CA Traveler wrote:


However consider: If the extension cord doesn't have the standard 30A female RV plug install one and buy a 30/50 adapter. Another option is buy a 50A extension cord and adapter, yes more expensive and heavy but allows for connecting to a 50A pedestal when it's to far from the RV. I occasionally run into this as there is absolutely no standard pedestal placement including even located on the passenger side.

The 30 amp cord does not have the standard 30 amp female RV plug. It is an extension cord.

Why add additional adapters in the line. Why not just cut off the standard 30 amp female end of the extension cord, install a 50 amp female RV plug, and wire it like it is a dogbone 30 to 50 amp adapter?

It essentially then becomes a longer adapter. That's why I was asking if the regular 30 to 50 amp adapter just wired L1 an L2 together to provide 120 volts at the trailer.

[CA_Traveler]

The 3 light household tester only provides a static check when you are watching in. A EMS continually checks wiring problems, high/low voltage etc and TURNS OFF POWER when there is a fault.

A open or partially open 50A neutral will cause high and low voltage and lets the smoke out. Not normally a home problem but to often 50A pedestal or RV plugs are worn or have loose wires - not good. You can maintain your RV plug but CG pedestals/wiring are all to often in bad shape.

[DutchmenSport]

"Why "top of the line"? "

I'll take a stab at this one as I use to be a die-hard ... "I don't need this at all" member!

We are at a campground right now. And believe it or not, just about 10 minutes ago we lost all power to the 5er (Montana High Country - 50 amp - both AC's running, it's hot). My laptop is on battery and my hot spot is my cell phone, so my laptop did not go out, nor my phone. But everything else in the camper did.

I checked the breakers in the camper first. All fine.
I checked the breakers in the shore panel power post. Nothing tripped. My Progressive 50 amp (portable) EMS just turned off and shut down the trailer. It did what it was supposed to do.

Power spike, or low voltage, don't know what happened, but something happened and the EMS shut the trailer down. I flipped the breaker at the pole, waited the 2 minutes and everything powered back up.

Air conditioners did not take a "hit" or fail due to low voltage, nor did the television get a sudden spike and blow up! Not to mention the residential refrigerator. I don't know if the EMS shut down because of spike or low voltage, most likely ... low voltage, as said, it's hot, and air conditioners are running everywhere right now all over the park.

Spikes, power fluxes, low voltage, sudden changes in voltages, you name it, a good EMS will protect the electronics inside the camper.

If plugged in at home, there not so much of a threat for provided electricity to fluctuate so much. I still keep the camper plugged into the EMS. However, at a campground, everyone plugged into the campground power is drawing, draining, exhausting, and taxing the electric lines and usage.

That's why you need a good EMS. (either permanently installed inside your camper or the portable one that connects at the campsite power pole)

[Lynnmor]

dryfly wrote:
Let me rephrase my OP. I fully understand AC split phase wiring of the 50 amp supply. I guess I don't understand how combing L1 and L2 in the dogbone adapter supplies 120 volts. Seems like it would produce 240 volts.

I'm asking this because instead of buying a 50 to 30 amp dogbone adapter, I want to take an old 30 amp extension cord and modify the trailer end with a 50 amp female plug, in essence build a 25' adapter.

L1 & L2 are combined in the plug so that they connect to only one hot leg in the pedestal. The other leg is ignored. You are correct in that there will be an unbalanced load on the pedestal side and if many customers are connected the same way it would be very inefficient. A few have built adapters in a way that they can select which side connects.

[CA_Traveler]

A 30A plug does not have 240V it is 120V only hence it cannot supply 240V to your RV. On your extension cord new 50A female connector connect gnd to gnd, neutral to neutral and 30A hot to BOTH 50A hots in the plug. This is how a 30/50A adapter is wired.

However consider: If the extension cord doesn't have the standard 30A female RV plug install one and buy a 30/50 adapter. Another option is buy a 50A extension cord and adapter, yes more expensive and heavy but allows for connecting to a 50A pedestal when it's to far from the RV. I occasionally run into this as there is absolutely no standard pedestal placement including even located on the passenger side.

[dryfly]

pianotuna wrote:


On a fifty amp--I do recommend a top of the line energy management system that may detect an open neutral.

Why "top of the line"? Why not just use the same AC outlet ground tester we use on 30 amp circuits? We are still just testing for open ground or neutral.

https://www.amazon.com/Electrical-Receptacle-Outlet-Ground-Tester/dp/B0012DHVQ0

[dryfly]

Let me rephrase my OP. I fully understand AC split phase wiring of the 50 amp supply. I guess I don't understand how combing L1 and L2 in the dogbone adapter supplies 120 volts. Seems like it would produce 240 volts.

I'm asking this because instead of buying a 50 to 30 amp dogbone adapter, I want to take an old 30 amp extension cord and modify the trailer end with a 50 amp female plug, in essence build a 25' adapter.

[DutchmenSport]

There is a very good YouTube video that explains in simple language the difference between 30 and 50 amp service. I refer back to it often: Click here.

I don't understand how it works, all I know is, the 50 amp service, the electric cord, and the trailer all work together to balance the 50 amps.

Manage your available electric Amperage usage, either 30 or 50 and let technology do what it is supposed to do, and just enjoy camping!

However, here's the formulaa used in the video.

120 volts X 30 amps = 3600 watts (I suppose that equal 2 electric 1500 watt space heaters, with 600 watts to spare).

120 volts X 50 amps = 6000 watts X 2 = 12000 watts (I suppose that equal 8 electric 1500 watt space heaters with zero watts to spare).

Good video. Watch it, it will help you understand.

[pianotuna]

Pretty hard to balance intermittent loads.

You may find dual air conditioning units have one on each leg.

It may be that the microwave is on one leg and the roof air on the other.

On a fifty amp--I do recommend a top of the line energy management system that may detect an open neutral.

[CA_Traveler]

Yes the 50A plug is 4 wire 3 pole and absolutely no concern about balancing loads. The 30/50 adapter works as you expect, your just limited to 30A total by the pedestal CB.

The 2 50A legs are combined (connected/shorted) in the adapter and NOT in the RV. When you plug into a 50A pedestal plug w/o the adapter you have 120/240V to the trailer panel with its dual 50A CB.

[BB_TX]

Read all about it here.

[2oldman]

You can either Google up a 50a wiring diagram or someone will be along shortly to provide one.