Question about 50 amp service

[Retired Gator]

I just bought a new 5th wheel, haven't taken delivery yet, but was told that i have 50 amp service/cord.  This raises three questions.

1) Does this automatically mean that i have 220V or can I have a 50 amp 110V system? 

2) I understand that many campsites don't offer 50 amp connections.  So should I buy a 30 amp to 50 amp jumper and just not run multiple large loads simultaneously?

3) If I do buy a jumper, do I need the "marine" connection, which I think my cord is, for $80, or the jumper cord, which is about $20?

Any help would be appreciated.

 

[Tom]

The marine connection and RV connection are different and have different plugs and receptacles. You won't be able to plug a marine 50A plug with its dog-leg locking pin(s) into a 50A campground receptacle. I doubt you have a marine cable and plug on your trailer.

Assuming you have an RV plug on the end of your trailer power cable, getting an adapter to plug into 30A campground power would allow you to plug into a 30A receptacle at a campground.

For an explanation of 50A RV power prepared by Winnebago technical staff, click the Library button above, select Tech Topics and click 30A vs 50A service.

 

[jd_is_me]

Tom,
I read that article from Winnebago on the differences between 50 and 30 amp service and it still wasn't too clear what the 50 AMP svc was (maybe I'm just a bit slow....at least that's what the wife says  :).  It sounds like it's a "dual 110V" supply or something other than a 220v; but would like for someone else to take a shot at explaining it.  Plus, if it's some sort of dual supply, how is that wired to the different appliances on board the RV so that all would have access to both legs.

 

[Tom]

Apologies, I was looking for a couple of diagrams that explain it a lot better than I can put in words. The Winnebago article is a little old and doesn't do a good job of explaining how current RVs are powered.

It sounds like it's a "dual 110V" supply or something other than a 220v

That's exactly the way I described it first time I saw how it's wired.

how is that wired to the different appliances on board the RV so that all would have access to both legs.

The loads are split between the two legs. There's also a power management system that offloads (locks out) some of the loads when you're plugged into 30A or 20A shore power. I haven't taken the time to figure out if the power management system actuallys moves loads from one leg to the other.

This is quite different from the 220V shore power on my boat. I have 220V appliances and 110V appliances, but everything in my coach is 110V or 12V DC.

 

[Ned]

With 50A service, you actually have two 50A circuits.  Your load center will split the various internal loads to one or the other of the two hot legs.  When you connect to 30A service (using an adapter) you will have one 30A circuit.  The adapter connects the two legs together into one as the 30A outlet has only one hot leg.

While there are campgrounds with only 30A service, we have no problem finding campgrounds with 50A.  For short stays, it's not a problem to have only 30A service available.  You do have to watch your loads however.  You won't run 2 air conditioners on a 30A circuit, and other high wattage appliances have to be used with care as well (microwave, hair dryer, etc.).

 

[jd_is_me]

....I poked around looking for additional info on exactly how this is hooked up and found this link which describes how to hook up an supply outlet from your home, but it also describes how most RV's are wired (usually just one of the AC's on the second leg, all of the other loads on the "primary" leg).  Interestingly, this looks like a 50A 220v circuit you'd find in your home for an electric range or clothes dryer.

http://users3.ev1.net/~crossstitch/RVWiring/wiring.html

 

[Ron]

If you look at the 50 amp connector for RVs from the pin side you will see three flat connectors or pins and one round connector. ?The upper flat center connector is neutral and the round connector is ground. ?The flat connectors on either side are the hot connectors. The voltage between either of the side flat connectors and Neutral is 120VAC voltage 50 amps which is what your RV uses. The voltage ?between the two side connectors is 220 VAC. This configuration is not use in your RV. ?The 30 Amp adapter is as Ned described.

 

[Gary RV_Wizard]

1) Does this automatically mean that i have 220V or can I have a 50 amp 110V system?

As others have explained, the standard 50A campground supply will indeed provide 220V service. Few RVs actually make use of the 220V availability and instead treat it as two 50A, 110V supply circuits.  That's because few RVs have any 220V appliances (but a few high end models will have 220V electric stoves and perhaps 220V dryers).  In the general case, some of the RV's electrical load will be placed on each  of the two 50A/110V circuits.  This allows the use of a 50A/30A adapter, which cross-connects the single 30A/110V supply to each of the input pins on your trailer's 50A plug and therefore delivers a modest amount of power to each. When doing so, you can run any of your rigs 110V loads, up to a grand total of 30A.

Once in awhile you may find a campground with 50A outlets that does not in fact provide 50A/220V service behind the 50A Rv outlet. Each of the two power pins in their connector may have 110V available, but there is not 220V between the two.  If you have no 220V appliances, you may never know this has occurred.  However, there may less total power available in this configuration, depending on the amp rating of each "leg" of the supply.  Sometimes it may be a simple 30A/110 circuit rewired to make it appear as a 50A connector. In that case, there would still be only 30A available, despite the 50A outlet.  You would find this out if you tried to run two air coonditionerss or a convection microwave and even one air conditioner (a circuit breaker will open).  But this is rarely a problem, so don't lose sleep over it. Noting is harmed and you simply have to adjust your power consumption to what is available. A complaint to the park owner would be in order, though. 

 

[Tom]

Once in awhile you may find a campground with 50A outlets that does not in fact provide 50A/220V service behind the 50A Rv outlet. Each of the two power pins in their connector may have 110V available, but there is not 220V between the two.

I didn't know that Gary and haven't yet come across it. In the marine world there are indeed 50A/110V receptacles, but they require a different plug from the 50A/220V plugs.

 

[caltex]

Gary, with the typical 50 amp RV circuit you could theoretically pull 100 amps (50 from each leg). Are the campgrounds wired with a neutral that could carry that current?

 

[Ned]

In a correctly 50A wired service, the two hot legs are out of phase by 180 degrees so the neutral current will never be more than the difference between the two.  If equal loads are on both legs, the neutral current is 0.  At most, it will be 50A if the load on one leg is maximum and none on the other.

 

[Ron]

Once in awhile you may find a campground with 50A outlets that does not in fact provide 50A/220V service behind the 50A Rv outlet. Each of the two power pins in their connector may have 110V available, but there is not 220V between the two.

As I recall the above described wiring configuration is not in compliance with the Electrical codes. 

 

[Ken & Sheila]

Ron,

You are right - dual 50amp 110 circuits in the same phase (IE no 220 between the legs) would be a serious violation of electrical codes for just the reason being discussed in the capacity if the neutral leg. If it were two 110 in the same phase the neutral wire would have to be capable of carring 100 amps. The cords on our motorhomes have the hot leads and the neutral sized for 50 amps. The neutral rarely carries more the 15 or 20 amps because of the offset between the two hot legs.

Ken

 

[John From Detroit]

Another somewhat related question..... Anyone have the "pin out" (wireing diagram) for a 30 amp 240 volt (4 wire) twist lock plug (such as on many portable generators).... I need to wire an outlet for such a beast, in truth, this has not much to do with RV and a lot to do with flakey commericial power, and I can always figure it out the hard way,,, but I thought I'd ask

 

[caltex]

Ned, you are right.  I wasn't thinking about the phase difference. But I guess you do need the same size wire  for the neutral as the hot legs.

 

[Ron]

Aside from possible fire hazards, dual 50amp 110 circuits in the same phase as Ned mentioned can be hard on air conditioners and other appliances. Just not a good idea.

 

[Ned]

John,

Check the manufacturer's web site.? I have found wiring diagrams for a lot of generators that way.  Or check out th page referenced by "jd is me" earlier in this thread.  It has diagrams for most of the common outlets.

 

[N Smock]

Gary, with the typical 50 amp RV circuit you could theoretically pull 100 amps (50 from each leg). Are the campgrounds wired with a neutral that could carry that current?

Not to worry each leg is a different phase, therefore the current is not cumulative but differencing.


Nelson

 

[Gary RV_Wizard]

The only places I have seen with non-standard 50A outlets had less than 50A available, typically a 30A circuit wired to a 50A box, with the single 30A line feeding both legs of the 50A connector.  This is just the same as using your own 50/30A dogbone. Anyway you cut it, the max you can draw is 30A, governed by the breaker at the other end.    I can also conceive of a 50A box  wired with both hot pins connected to just one leg of a 220V/50A supply. Again, the max draw would be 50A total (e.g. 25/25 or 40/10) and the neutral in the RV cord would never exceed 50A.  No problem, except that you only have 5500 watts available instead of the 11,000 you were expecting.  For most situations, 5500 watts is plenty.

It would have to be rare indeed to find a box with two independent but in phase 110/50A feeds to a 50A outlet, such that the 100A neutral problem could occur. The reason is simply that there is no benefit to the campground to do so and even a shade tree electrician would have to go to extra lengths and expense to screw up in that manner.  That said, there is undoubtedly a campground somewhere with just that crzy situation, cause just about every sort of ridiculous wiring exists in campground electrical services.  And ditto for plumbing as well.

 

[Ned]

Gary, you may remember that campground in FL where the 50A service was wired with 30A breakers.