30 Amp vs. 50 Amp hookups

We are spending two months in Florida.  One month each at Williston Crossings RV Resort, http://willistoncrossingrv.com/, and Rock Crusher RV Park http://www.rockcrushercanyon.com/ (just found out they both happen to be on the just released 100+ Top Rated Good Sam Parks, http://www.goodsamclub.com/travel/topparks.aspx).  Anyway, the daytime temperatures at both have been in mid 60s to upper 70s, but have had a couple of nights with lows in the upper 20s at both and have used two electric heaters at both along with the tank heaters.  At Williston Crossings, the plug-in voltmeter dropped to 108v with both heaters running and tripped a breaker once.  But at Rock Crusher, the voltmeter stays just about on 120v.

One difference in the parks: strangely Rock Crusher offers only 20 Amp and 50 Amp connections, so a 50 Amp to 30 Amp adapter is required.  So was wondering, does plugging into 50 Amps with an adapter furnish a better level of power than plugging directly into 30 Amps?  Or is it a difference in the parks?  I always assumed it wouldn’t make any difference, but I don’t know that much about electricity.  Wish I’d tried that adapter at the first park but it never occurred to me.

I have a 50amp/220V outlet in my garage at home.  When I plug in at home, I use the adapter shown below.  It utilizes only one of the two 220v hot wires.  Given my 50amp circuit in the garage works off two 25amp circuit breakers in the house, it is easy to concluded that it provides 25amp service to my PC.

I think you would need 60amp/220v service at the peg to get 110v/30amp service from such an adaptor.  But RV parks don't offer that.

If you can't get enough power to run two electric space heaters along with the rest of your PC, I advise to buy a typical 110v 12gauge 25 or 50 foot extension cord and run it from the power peg (20amp) through one of the van doors to supply independant power to your strongest electric heater.  Just be sure the door doesn't pinch the cord.  You might have to place a tiny 1/2" thick piece of soft pine in the door jamb (low corner opposite the hinges) to maintain a 1/2" gap.  The cord should be easily push and/or pulled through the door gasket.



A 25 foot 12 gauge extension cord like this can be purchased at any home improvement center.

I have a 50amp/220V outlet in my garage at home.  When I plug in at home, I use the adapter shown below.  It utilizes only one of the two 220v hot wires.  Given my 50amp circuit in the garage works off two 25amp circuit breakers in the house, it is easy to concluded that it provides 25amp service to my PC.

Hi Ron,

I hate to do it, but I have to challenge this; two 25amp 110V breakers ganged together will provide one 25amp 220V outlet, not 50amp.  Irregardless, as you said, the adapter will provide 25amp 110V to the RV.

When using the adapter on a 50amp 220V service, you will have a 50amp 110V service.  This would explain why gophoenix didn't trip the breaker when using the adapter.  The power post at the RV site will have one 20amp breaker, one 30amp breaker and two 50amp breakers ganged together.

Actually, most RVs that use 50amp service are set up for two 50amp 110V main breakers in the rig, not 220V.  That is why there are four prongs, two 110V hot, one neutral and one ground.  You need the neutral to get the 110V service from each hot lead, if you wanted 220V, you would wire between the hot leads and not use the neutral.  The 30amp plug has three prongs, one each hot, neutral and ground.  The adapter uses one of the 50amp hot leads, neutral and ground.  One 30amp 110V service equals 3,300 watts, two 50amp 110V services equals 11,000 watts of power; that is why the 50amp cord on those class As is so large.

Using the adapter presents a potential problem, the 30amp power cord from the RV is now attached to a 50amp breaker.  If there is a short before the 30amp breaker in the RV then the 30amp power cord and wiring up to the RV breaker panel is not properly protected; however, if the short is on the RV side of the RV breaker panel then the 30amp RV breaker will do it's job.

Bob

.....two 25amp 110V breakers ganged together will provide one 25amp 220V outlet, not 50amp.

Please Bob, Don't applogize.  Correct me when I got my story wrong.  I am no authority on this stuff.  I thought 25a/110v + 25a/110v = 50a/220v.  But you say it goes 25a/110v + 25a/110v = 25a/220v.

I will have to study what I have in my main breaker box more closely.  I thought I had two 25 amp breakers.  Maybe I got it mixed up as to what I have in the house.  I do recall the fellow who initially wired my garage had a different style 220v receptacle in there, later switched to this style to accomodate the RV adaptor.  Do the different style receptacles have different power ratings?

Quote from: bobander on January 03, 2012, 01:06:58 pm

.....two 25amp 110V breakers ganged together will provide one 25amp 220V outlet, not 50amp.

Please Bob, Don't applogize.  Correct me when I got my story wrong.  I am no authority on this stuff.  I thought 25a/110v + 25a/110v = 50a/220v.  But you say it goes 25a/110v + 25a/110v = 25a/220v.

I will have to study what I have in my main breaker box more closely.  I thought I had two 25 amp breakers.  Maybe I got it mixed up as to what I have in the house.  I do recall the fellow who initially wired my garage had a different style 220v receptacle in there, later switched to this style to accomodate the RV adaptor.  Do the different style receptacles have different power ratings?

Ron,

Yes, the receptacles are rated differently, 50amp and 30amp.  You could have a 50amp receptacle supplied by 25amp breakers, the 25amp breakers are protecting the wiring as well as the receptacle.  The wiring is likely limited to 25amps.  You may have had to change the receptacle to get access to the neutral wire up so that you could have 110volts not 220.  Sometimes electricians will run the neutral but not use it at the receptacle if only 220 volts is desired.  If you have 25amp breakers, then you can use one 25amp 110volt breaker for the RV by using the adapter, and you could also have 220volt 25amp for a welder if you use a matching plug wired to the two hots and not the neutral.

Yes, two 25amp 110V = one 25amp 220V.  It is the same total power: 2 x 25 x 110 = 5,500 watts and 25 x 220 = 5,500 watts.

This is informative:

http://www.rv-motorhome-answers.com/AC-Electricity.html

Bob

So Bob, if both a 30 Amp and 50 Amp are available, it's safer to use the 30 Amp outlet rather than the 50 Amp with an adapter?

So Bob, if both a 30 Amp and 50 Amp are available, it's safer to use the 30 Amp outlet rather than the 50 Amp with an adapter?

Yes, the RV power cord and wiring up to the RV breaker panel are rated for 30 Amp and using the 50 Amp with an adapter could allow greater than 30 Amp in the unlikely event of a cord or wiring failure.

I do use the adapter if there is only a 50 Amp outlet avaiable, I figure that there is a low probability of a failure and it would hopefully happen when usually plugged into a 30 Amp outlet and then be protected.

Bob

I plan on installing an out side electric door and run a 25' 12 gauge extension cord inside the rig, then I can hook up to the 30amp for the rig and the 15amp for the heater or ?????

Billy, sounds like that could be a good idea. Let us know how that works out/how you did it.