John From Detroit
Well-known member
Ned said:
Thanks, will do
Question about 50 amp service
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Thanks, will do
Gary RV_Wizard
Site Team
Ned said:
Indeed I do, Ned. It was your experience there that led me to research how 50A connectors should be wired and the several ways they can be inappropriately wired. And now that I have worked in some campgrounds, I have seem some of them first hand!
You find these rather strange set-ups when an older campground's 20 or 30 amp service has been partially upgraded to accomodate newer 50A rigs. Completely re-doing the campground electrical system for proper 50A power is a BIG deal, very expensive. That's why some of these schemes get concocted.
Here's what might happen. and it is not really unreasonable. A typical 30A RV pedestal also has 20A outlets. Most such boxes are designed to be served with a 220 circuit, with one leg powering the 30A outlet and the other the 20A outlet. The power source will have a dual 30A breaker. It is straight-forward to replace the 30/20 box with a 50A box that has no 20A outlets and use the existing wiring to power it. It works (even for a Prevost with a 220V electric stove) and does not violate any codes I know of, but you end up with only 30A available on each leg. Whether it is ethical to rent this as a "50A site" is another question!
blueblood
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RV Roamer said:
I have seen campgrounds advertise 100 amp pedestals. I'm never sure what they are saying i.e 50/30/20 or that the 50 receptacle has capability for 100. Do you know ?
Although I've never seen any ads for 100A service, it could mean they have 2 50A outlets available for some of the newer all electric coaches that need it.
Or they may be indulging in a bit of hyperbole as all correctly wired 50A RV circuits have 100A available.
Or they may be indulging in a bit of hyperbole as all correctly wired 50A RV circuits have 100A available.
John From Detroit
Well-known member
Ned said:
Well, somewhere (Murphy's laws for niave young engineers, Technically that should include me at one time, Since I studied to be an engineer even if I never got there) it is written
"Discount all advertising claims 50%, Discount all salesman's claims 75%, and I forget the discount for "Manafacturer's claims)
So, if it's advertised at 100 amp, and you discount 50% as instructed by Murphy... Then you got 50 amp service,
Strange thing... I've been in exactly one campground with 50 amp service, usually use a 30 to fifty adapter, which gives me a true 30 amp total, (3600 watts at 120 volts) and I have NEVER, not once, tripped said 30 amp breaker
Both AC's a microwave and a television, hot water and fridge, and the only thing that has tripped is the breakers for the AC inside the rig... (They tirp for no reason I can fantom... I suspect they "Trip" from pot holes in the road (Impact turns them off) since the power panel is in a high impact area (Right over the rear axel)
The amazing thing is the converter alone can drag a killowat off the line if the house batteries are exhausted.
(You should have heard my spare kilowatt the day I used it to recharge the house battery enough to fire up the onan before I found the Emergency start switch works both ways if the engine is running)
(Fired it up, settled it down, Plugged in the rig and ..... Suddenly it was running at full load!!!!
blueblood
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Found this explanation of RV Park power supply interesting -you might too. He is responding to a person who had virtually his whole RV electrical system and appliances fried in a Thousand Trails CG due to an apparently improperly repaired pedestal.
this is a topic that confuses even professional electricians and gets argued frequently on other formums, where arguing seems to be more important than answering the question. I'll take a stab at trying to answer without getting too technical.
The RV electrical service supply is a 4 wire Y system, where L1,L2,L3 are the 3 - 120 volt phases (we only use 2 of them) and the center of that Y is the 0 potential, or neutral. Most folks understand that in your home wiring service the neutral & ground are tied together or "bonded" for safety to assure any short circuits flow to ground. Your RV neutral is "unbonded", since it relies on the RV power supply path back to the source where it is tied to earth ground. This 4 wire Y setup for the RV is also an "unbalanced" system, meaning the neutral almost always has significant currents flowing in it. If your L1 circuits have 30 amps of current, and L2 has 0, then the shared/common neutral has 30 amps. Only in the unusual or theoretical case when L1 and L2 circuits are evenly loaded, is the neutral current 0. Next and more to the point of the open neutral problem, remember that L1 and L2 as well as Neutral and Grnd are tied all the way back to the supply source transformer; and that we're dealing with multi phase taps on that transformer. i.e. L1 and L2 are out of phase, and the neutral and ground are tied to the mid point of those two phase legs. When something happens to open the neutral line to your RV, which removes the 0 potential reference point and the return path for L1 & L2, then the reaction of the 2 phases back at the point of supply (where they are still connected together) forces the Ground point potential to surge up to approximately 69 volts (240 / 2x sqrt 3) and causes a current rush between L1, L2 and Grnd. thats what causes the electronics to get fried.
Its hard to put this into clear non technical words and I'm sure someone will find fault with this explaination. I'll take no offense if someone can explain it better. For more details research Alternating Current electrical theory, particularly 4 wire wye services.
this is a topic that confuses even professional electricians and gets argued frequently on other formums, where arguing seems to be more important than answering the question. I'll take a stab at trying to answer without getting too technical.
The RV electrical service supply is a 4 wire Y system, where L1,L2,L3 are the 3 - 120 volt phases (we only use 2 of them) and the center of that Y is the 0 potential, or neutral. Most folks understand that in your home wiring service the neutral & ground are tied together or "bonded" for safety to assure any short circuits flow to ground. Your RV neutral is "unbonded", since it relies on the RV power supply path back to the source where it is tied to earth ground. This 4 wire Y setup for the RV is also an "unbalanced" system, meaning the neutral almost always has significant currents flowing in it. If your L1 circuits have 30 amps of current, and L2 has 0, then the shared/common neutral has 30 amps. Only in the unusual or theoretical case when L1 and L2 circuits are evenly loaded, is the neutral current 0. Next and more to the point of the open neutral problem, remember that L1 and L2 as well as Neutral and Grnd are tied all the way back to the supply source transformer; and that we're dealing with multi phase taps on that transformer. i.e. L1 and L2 are out of phase, and the neutral and ground are tied to the mid point of those two phase legs. When something happens to open the neutral line to your RV, which removes the 0 potential reference point and the return path for L1 & L2, then the reaction of the 2 phases back at the point of supply (where they are still connected together) forces the Ground point potential to surge up to approximately 69 volts (240 / 2x sqrt 3) and causes a current rush between L1, L2 and Grnd. thats what causes the electronics to get fried.
Its hard to put this into clear non technical words and I'm sure someone will find fault with this explaination. I'll take no offense if someone can explain it better. For more details research Alternating Current electrical theory, particularly 4 wire wye services.
I have never seen a campground wired with 3-phase service, only 2-phase or single phase. He may be confusing the 4-wire circuit (hot1, hot2, neutral, ground) with a true 3-phase circuit (hot1, hot2, hot3, neutral) which would also have a separate ground.
In manu RVs, the neutral is in fact incorrectly bonded to the ground, which will result in tripping any GFCI outlets you may plug into. I know, mine is that way.
In manu RVs, the neutral is in fact incorrectly bonded to the ground, which will result in tripping any GFCI outlets you may plug into. I know, mine is that way.
Gary RV_Wizard
Site Team
As Ned notes, each RV site itself does not receive three phase power, nor is there any way to hook up three hot wires in the box.
The "rush" or surge caused by an open neutral can indeed occur, though it is important to remember that back at the transformer where the three-phase power exists, the power for a lot of sites is combined and that generally evens out the unbalanced effect at that point. But if only one of the sites powered from the distribution transformer was occupied at the time the neutral went open, then [I think] the entire surge might feed back to one site.
Whatever the explanation, surges can and do occur for a variety of reasons and a surge protector can be a valuable tool if you are in their path. Protectors that include detection of conditions such as an open neutral can also help. That said, I have lost just one VCR to electrical surges in 10 years of Rvig without a surge protector on my shore line. And I'm not even sure it was shore power that smoked the VCR - I had also used my genset during the period it failed.
The "rush" or surge caused by an open neutral can indeed occur, though it is important to remember that back at the transformer where the three-phase power exists, the power for a lot of sites is combined and that generally evens out the unbalanced effect at that point. But if only one of the sites powered from the distribution transformer was occupied at the time the neutral went open, then [I think] the entire surge might feed back to one site.
Whatever the explanation, surges can and do occur for a variety of reasons and a surge protector can be a valuable tool if you are in their path. Protectors that include detection of conditions such as an open neutral can also help. That said, I have lost just one VCR to electrical surges in 10 years of Rvig without a surge protector on my shore line. And I'm not even sure it was shore power that smoked the VCR - I had also used my genset during the period it failed.
Tom
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I think he's confused too. My electrical theory was a long time ago, but 4-wire Y-connected (or "star" where I went to school) doesn't give you 240V between 2 of the 120V hot wires because they're not 180 degrees out of phase with each other.
blueblood
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RV Roamer said:
He doen't say that. He's talkiing about the transformer and then says only two are used. However, I checked NEMA code and in particular I went to a Q & A on RV park wiring and found this
Code says the following in one of their Q&A's
Because of their rural nature, many RV parks are supplied by 120/240 volt, single-phase services and the size of such services is often limited by the serving utility. Another point regarding the voltage characteristics of a service supplying sites equipped with 50 ampere, 125/250 volt, single-phase receptacles is that the utilization voltage at the RV sites is required to be 120/240 volts nominal. A three-phase, four-wire, 208Y/120 volt service is not permitted as the supply voltage for RV sites equipped with 50 ampere, 125/250-volt receptacles, as the line-to-line voltage is 208 volts. Such systems are permitted to supply sites equipped only with 125 volt, 20- or 30-ampere receptacles
In real Layman terms what is the difference between an RV park 50 AMP plug (neutral top, 2 hots on the side pins, and ground on the bottom and a 220V dryer plug in a house?
Ron tried to explain this to me in Montana but it did not sink in, I fried a sat receiver on our trip in Indiana when a friend convinced me he had a plug in the hangar for his new RV.
Guess he wanted it tested. :-\ :-\
Ron tried to explain this to me in Montana but it did not sink in, I fried a sat receiver on our trip in Indiana when a friend convinced me he had a plug in the hangar for his new RV.
Guess he wanted it tested. :-\ :-\
John From Detroit
Well-known member
Jeff, there are basically 2 differences
1: Dryer is normally 30 amp
2: Pins are a different shape, size, and the placement is a bit different (Spacing and the like)
That folks, is all there is to it, Mostly it's #2 by the way
Electric stove plugs... Those can be 50 amp, same as the RV, however note that they too are a different size and spacing and shap of pins.
The big difference in all 3 cases is the physical shape of the plug and pins, nothing more
1: Dryer is normally 30 amp
2: Pins are a different shape, size, and the placement is a bit different (Spacing and the like)
That folks, is all there is to it, Mostly it's #2 by the way
Electric stove plugs... Those can be 50 amp, same as the RV, however note that they too are a different size and spacing and shap of pins.
The big difference in all 3 cases is the physical shape of the plug and pins, nothing more
