Newbie Question ref 50 amp service

[Wally15]

30 amp service is 30 amps at 120V, right? 50 amp service is 50 amps at 240V, also right? But everything in my TT is 120V (or 12V), so I actually have TWO 50 amp 120V legs for a total of 100 amps service load. So 50 amp service isn't 1.67 x the 30 amps, it's 3.33 x the 30 amps service.
Or am I totally missing something here?
Florida summers is making me think seriously about the 2nd a/c.

[Bob Landry]

There have been many 50A threads on different forums and in almost all of them, the armchair engineers come out of the woodwork and start confusing everyone with their formulas and calculations. In the process there is usually some information that is wrong or in some cases, just downright dangerous.
For all practical purposes, which is what we basically need to know, is that if you have 50A service in your trailer, you have two 120V legs capable of supplying 50A each, for a total of 100A of available power. There may be some loss because of voltage drops, wire length, etc, but essentially it's 100A of usable power.
If you have 30A service in your trailer, you have 50A available at the pedestal, but you will be limited to a single 30A source by the circuit breaker in your distribution panel.

[geo]

Very true, Bob. Except, the 30 amp socket at the pedestal is controlled by a 30 amp breaker. (One hot lead, one neutral, and one ground). On the 50 amp side, as you said, there are two 50 amp breakers - one each controlling each hot supply leg. (Two hot leads, one neutral, and one ground)

Wally15, just the mention of Florida implies to me - two AC units. You need two to control the humidity associated with the very warm air. Besides, two ACs gives you a backup.

Ron

[Wally15]

Thanks. I thought that was how it worked. Glad I got the TT with the 50 amp upgrade. Makes up for a couple of things I didn't get but sorta wanted in this slightly used TT.

[Bob Landry]

I think we're saying the same thing. For some reason I was basing my comment on the scenario of plugging a 30A cord into 50A service where the pedestal power would be protected by 50A breakers, but the 0a breaker in the trailer wold trip long before the pedestal breaker wold trip.

[GaryWT]

I think you have it wrong. 50a is one leg at 120. The 2 legs that you say is how your electric dryer plug is wired. If you plug your trailer into a 240 plug you will fry everything in it.

[B&T]

Bob and Geo are correct.

[Stublejumper]

Originally Posted by B&T

Bob and Geo are correct.

X2 for Bob and Geo

[DJ85]

Armchair engineers,!!!!!!!!!!!. Now thats funny.

[SAD]

Originally Posted by GaryWT

I think you have it wrong. 50a is one leg at 120. The 2 legs that you say is how your electric dryer plug is wired. If you plug your trailer into a 240 plug you will fry everything in it.

Gary, everyone else is correct.

An RV 50 amp outlet is a 125/250V 60 hz 50 ampere supply.

[Bob Landry]

Originally Posted by GaryWT

I think you have it wrong. 50a is one leg at 120. The 2 legs that you say is how your electric dryer plug is wired. If you plug your trailer into a 240 plug you will fry everything in it.

50A service for RVs is two legs with 120V each. The shared neutral make each leg 120V and each of those legs provides 50A for a total of 100A of available power. The dryer plug in your stick & brick is probably only 2 wire 240V because 240V appliances do not need 120V, thus no neutral.

There are stories of people burning up rigs by plugging into 240V but I think you'll find that in almost all, if not all, of the cases, the plug was mis-wired by a "licensed" electrician who was not familiar with RV wiring or an unknowing owner and he wired 240V to a 30A RV plug. There are 240V/30A plugs, but the orientation of the prongs on the plugs are different, and it's impossible to plug a standard RV plug into 240V without someone doing something stupid.

That's what makes the posting of 50A information on forums so scary. There's a lot of misinformation on the Internet as well as "brother-in-law" info that gets parroted that is dangerous and in some cases fatal. Unfortunately all who surf the web do not know how to weed out the bad information and I'm betting there is a lot of equipment damage and personal injury caused caused by it that we just don't hear about.

Bottom line, if you don't understand electricity, don't post comments about it. You could seriously injure someone.

[ddmay]

To all of you newbies and "professional electricians" Better listen to Bob Landry, I'll bet he was an electrician in his former life. Read,believe, and understand his bottom line.

[Steve S]

Good advice Bob Landry, most people don't understand that electrical shorts from bad wiring don't only happen when the breaker is flicked they can happen at anytime and flames move fast.
When I was searching the interweb about 30 and 50 amps I found myself scratching my head and when I doubt myself I always call the pro's.
My neighbor is a commercial electrician and he came over and checked everything to make sure that everything I did was safe and that made me sleep better at night.

[geo]

Yes, Bob is correct. Sorry about the 30 amp pedestal misunderstanding.

And he is correct, if you don't truly understand electrical circuits and application, don't! Call someone who is a licensed electrician and even then, ask for references! Not all electricians understand how RV hook-up wiring works!

Just as a side note, on a thread a long time ago (and still on the forum), there was mention that parks were wired using "3-phase / 6-phase" power. I didn't post a reply to this thread, but this "wiring" is probably not the case. Some Class A Motorhomes and high-end fifth wheels actually are wired to use the 240VAC power that can be available from the standard "50 amp connection". If the park was not wired with the proper "180 degrees out" 240VAC . . . well, it could be an expensive hookup! Again, like Bob mentioned, if you are not well versed in electricity and RV applied electrical applications, DON'T!

Ron

[GaryWT]

Ok I stand corrected. I have read too many burning up their equipment and did not want to see it again.

[bobbecky]

Not intending to throw more confusion in this subject, but here goes. You must get a decent volt meter to verify voltage at the pedestal before plugging in if you don't have some form of protective device in your system. The problem is, you will find the occasional park that is wired off of a three phase, 208y/120V transformer, and when checking voltage at the pedestal, you will have two 120V legs, but when looking for 240V between the two hot legs, you will only see 208V. There is nothing wrong with this voltage, and your RV will not have a problem, unless it is the rare unit that has some appliance that needs 240V. And in this thread, it was mentioned that the two 120V hotlegs on a 50amp service are 180 degrees out, in reality, the 240V legs are 120 degrees apart, and at the utility transformer, the 240V is grounded in the middle of the transformer coil and that is how the two 120V legs are created from the 240V.

[SAD]

Originally Posted by bobbecky

Not intending to throw more confusion in this subject, but here goes. You must get a decent volt meter to verify voltage at the pedestal before plugging in if you don't have some form of protective device in your system. The problem is, you will find the occasional park that is wired off of a three phase, 208y/120V transformer, and when checking voltage at the pedestal, you will have two 120V legs, but when looking for 240V between the two hot legs, you will only see 208V. There is nothing wrong with this voltage, and your RV will not have a problem, unless it is the rare unit that has some appliance that needs 240V. And in this thread, it was mentioned that the two 120V hotlegs on a 50amp service are 180 degrees out, in reality, the 240V legs are 120 degrees apart, and at the utility transformer, the 240V is grounded in the middle of the transformer coil and that is how the two 120V legs are created from the 240V.

If you find this, it is WRONG and not to code.

[Bob Landry]

Originally Posted by bobbecky

Not intending to throw more confusion in this subject, but here goes. You must get a decent volt meter to verify voltage at the pedestal before plugging in if you don't have some form of protective device in your system. The problem is, you will find the occasional park that is wired off of a three phase, 208y/120V transformer, and when checking voltage at the pedestal, you will have two 120V legs, but when looking for 240V between the two hot legs, you will only see 208V. There is nothing wrong with this voltage, and your RV will not have a problem, unless it is the rare unit that has some appliance that needs 240V. And in this thread, it was mentioned that the two 120V hotlegs on a 50amp service are 180 degrees out, in reality, the 240V legs are 120 degrees apart, and at the utility transformer, the 240V is grounded in the middle of the transformer coil and that is how the two 120V legs are created from the 240V.

And this is an example of my previous statement about engineers trying to put everyone into information overload. Is there that much of a problem in keeping the discussions so that the layman can understand what's going on?

[Festus2]

Originally Posted by Bob Landry

And this is an example of my previous statement about engineers trying to put everyone into information overload. Is there that much of a problem in keeping the discussions so that the layman can understand what's going on?

Bob -

Well if you were to take a look at this and similar electrical threads as well as some of the recent tire threads, there might indeed be a problem trying to keep discussions so that "the layman can understand what's going on".

We can all agree that "armchair engineers and experts" can get us into serious trouble - especially when it comes to electricity. You can't be fooling around with something that can kill you.

So where does all of this leave the poor newbie who asks, what appears to be a fairly simple question about tires or electricity, and ends up having to read lengthy and technical dissertations or is given incorrect information that has the potential to harm? Is he supposed to weed through all this stuff and make sense from it? Does he assume that what he is being told on here is correct? How does he separate fact from fiction?

I guess conflicting and erroneous advice are sometimes a part of what forums are all about. There will always be armchair engineers ready to offer their advice whether it is asked for or not. And sometimes, the more complex and complicated it is, it somehow makes the "experts" feel like they have accomplished something.

So, getting back to our "newbie" friend who just asks a simple question and would, I think, appreciate a concise and factual answer........ I often feel for the poor guy or gal. I can just hear him/her muttering ..."I didn't think that life was so darn complicated".

[Wally15]

As the OP on this thread, I did not mean to create confusion and/or dissention among the group with my question about total available amps on a 50 vs 30 amp service. I was trying to make sure that adding a 2nd a/c wouldn't overly tax my available amperage after hearing so many comments about "turning this off in order to use this or else a breaker will pop".
I'm a new RV'er setting up an RV for extended stays (all summer) in the FL Panhandle. I don't want to be hauling it back and forth for mods and additions. I'm going to add the 2nd A/C, and I'm going to do it myself. The TT is wired for 50 amps, and even has the wiring run for the 2nd A/C. So hopefully it will be a "plug 'n play", assuming I don't drop it through the roof. I also ordered an EMS (PI HW50C) to protect the TT from lightning and other electrical mishaps. That's about all the major projects I plan to do before hauling it to the coast. Hopefully any other mods can be easily (?) done on site. Or have I missed something important?
It's not the heat, it's the humanity!