Plugging 30A 5th wheel into 50A service

klassic wrote:

Me Again wrote:
The way a four wire 240V circuit works you have a ground, neutral, and two 120 hot phases. 240V appliances just use the two hots and ground. A 120V appliance uses one or the other hot and neutral. If neutrals path to the reference source is broken, then a 120V finds the path to the other 120V phase and you have 240 across the appliances, smoke and smell.

Ecample.

Refer on phase one and neutral =120V
Microwave on phase two and same neutral = 120V

Neutral burns up in at power pole(common occurrence). Phase one comes in on hot lead to refer and goes out neutral, then finds no route to source. It does however find a route via the microwave's neutral and on out to the other phase 120V. 120+120=240 volts across the two devices. Repeats across other devices on the two source phases. Low resistance devices burn up one after another working towards higher resistant devices.

Chris

Sorry about the hijack
I understand your example.... But wouldn't the main ground wire have to burn up too for this to happen?
If I yank the neutral wire out of my home's service panel... All the circuit's neutrals still tie into ground.
Or are RV panels wired differently?

http://en.wikipedia.org/wiki/Ground_and_neutral

For Coach Man from this link, this is how RV parks work:

Split phase
Main article: Split-phase electric power
In split-phase wiring, for example, a duplex receptacle in a North American kitchen, devices may be connected with a cable that has three conductors, in addition to ground. The three conductors are usually coloured red, black, and white. The white serves as a common neutral, while the red and black each feed, separately, the top and bottom hot sides of the receptacle. Typically such receptacles are supplied from two circuit breakers in which the handles of two poles are tied together for a common trip. If two large appliances are used at once, current passes through both and the neutral only carries the difference in current. The advantage is that only three wires are required to serve these loads, instead of four. If one kitchen appliance overloads the circuit, the other side of the duplex receptacle will be shut off as well. This is called a multiwire branch circuit. Common trip is required when the connected load uses more than one phase simultaneously. The common trip prevents overloading of the shared neutral if one device draws more than rated current.

Coach-man wrote:
The original question was can I plug a 30 amp RV into a 50 amp outlet, the answer was yes with an adaptor! Someone, mentioned that, that was dangerous, it is not, in fact several posts indicated that is was less likely to have a problem, brownouts, triped circuit breakers, etc by plugging into the 50 amp outlet, too which I agreed. At least one person disagreed and went into an esoteric discussion on wiring, and that it was the same regardless of which plug was used. I disagreed and continue to disagree! A "50 amp" plug is actually 100 amps total, that is two 120 volt 50 amp feeds with a common neutral. You can get real close to overloading a 30 amp circuit, but you have more cushion, with a 50 in a rig designed for 30 amp service. If there is a problem, your main circuit breaker in the rig would blow long before your pedistal breaker would go, and no you can not draw more than the maximum of 30 amps, and in a 30 amp rig with adaptor there is no way of seeing 240 volts in your rig! Even in a 50 amp rig, 240 volts to your equipment would be unlikely due to the fourth lead, ie ground!

So much misinformation in a single post. I brown out in the park power will be the same if you are plugged into a 30amp breaker or a 50 amp breaker with an adapter. The source on the 30 amp breaker and the 50 breaker are the same buss in the power pole. The breakers clip onto the same exact buss. To keep the neutral balanced on each power run through sections of the park, the 30 amp breakers are alternated on the two power phase busses. In a perfect world the neutral has little to no current flow back to the source, as the two phases cancel out.

BTW loose neutral when you have a 30 amp service just kills you power. This happen two days in a row while we were in Hemet in January and Golden Village Palms RV resort. I watched and talked to the maintenance guys while they repaired it. The first day they miss the neutral buss problem. Quote from them: "Be glad you are not a 50 amp coach/trailer!" My friend that was two sites over and who we stopped to see, said last week a guy burned up all the stuff in this MH! Duh!

More cushion on a 50 breaker. I 30 amp breaker is a 30 breaker, the one in trailer will not let you have more cushion!

Fourth lead?? The ground and neutral are not common in the trailers wiring. The ground is there to protect you, and you better not connect it to the neutral in the trailer. They are separate back to the main distribution panel.

"in a 30 amp rig with adaptor there is no way of seeing 240 volts" This is the only true statement you made.

We are all here to learn and people with both 30 and 50 rigs will read these posts.

http://en.wikipedia.org/wiki/Brownout_%28electricity%29

Chris

Me Again wrote:
The way a four wire 240V circuit works you have a ground, neutral, and two 120 hot phases. 240V appliances just use the two hots and ground. A 120V appliance uses one or the other hot and neutral. If neutrals path to the reference source is broken, then a 120V finds the path to the other 120V phase and you have 240 across the appliances, smoke and smell.

Ecample.

Refer on phase one and neutral =120V
Microwave on phase two and same neutral = 120V

Neutral burns up in at power pole(common occurrence). Phase one comes in on hot lead to refer and goes out neutral, then finds no route to source. It does however find a route via the microwave's neutral and on out to the other phase 120V. 120+120=240 volts across the two devices. Repeats across other devices on the two source phases. Low resistance devices burn up one after another working towards higher resistant devices.

Chris

Sorry about the hijack
I understand your example.... But wouldn't the main ground wire have to burn up too for this to happen?
If I yank the neutral wire out of my home's service panel... All the circuit's neutrals still tie into ground.
Or are RV panels wired differently?

The original question was can I plug a 30 amp RV into a 50 amp outlet, the answer was yes with an adaptor! Someone, mentioned that, that was dangerous, it is not, in fact several posts indicated that is was less likely to have a problem, brownouts, triped circuit breakers, etc by plugging into the 50 amp outlet, too which I agreed. At least one person disagreed and went into an esoteric discussion on wiring, and that it was the same regardless of which plug was used. I disagreed and continue to disagree! A "50 amp" plug is actually 100 amps total, that is two 120 volt 50 amp feeds with a common neutral. You can get real close to overloading a 30 amp circuit, but you have more cushion, with a 50 in a rig designed for 30 amp service. If there is a problem, your main circuit breaker in the rig would blow long before your pedistal breaker would go, and no you can not draw more than the maximum of 30 amps, and in a 30 amp rig with adaptor there is no way of seeing 240 volts in your rig! Even in a 50 amp rig, 240 volts to your equipment would be unlikely due to the fourth lead, ie ground!

The way a four wire 240V circuit works you have a ground, neutral, and two 120 hot phases. 240V appliances just use the two hots and ground. A 120V appliance uses one or the other hot and neutral. If neutrals path to the reference source is broken, then a 120V finds the path to the other 120V phase and you have 240 across the appliances, smoke and smell.

Ecample.

Refer on phase one and neutral =120V
Microwave on phase two and same neutral = 120V

Neutral burns up in at power pole(common occurrence). Phase one comes in on hot lead to refer and goes out neutral, then finds no route to source. It does however find a route via the microwave's neutral and on out to the other phase 120V. 120+120=240 volts across the two devices. Repeats across other devices on the two source phases. Low resistance devices burn up one after another working towards higher resistant devices.

Chris

Me Again wrote:
...

The worst condition people face is those with full 50 service. If the neutral lead goes bad, then 240V is placed across everything in the trailer or coach, and you burn up TVs, micro waves, converters, inverters, stereos, and sat equipment. Friend had that happen this winter in California. His bill to date is 7K and they are not done replacing things.

If you have full 50 service, have a good isolation device that will protect you from this happening.

"The lack of knowledge about how electricity works makes you wonder???"

Chris

I need an explanation to this ....:h


If the neutral goes bad?...you mean disconnects or gets cut?
Then how would that transfer 240 to any plug inside the RV?
The 120V receptacle just wouldn't work anymore...and I'm thinking it might still work because the bond wire is there.

How would the one leg of the 120V come into contact with a receptacle wired to the opposite 120v leg to make 240v?

And if the neutral came into contact with either 120v wire, it would just short out and blow the pedestal breaker.

Pando2......see what you did now!!! :)

Coach-man wrote:



30 amp and 50 amp uses the same wiring? 30 amp uses 12 gauge wire, 50 amp uses 10 gauge wire! They better not be using the same wires! I guess some parks will try and get by using the same wires, but that is so wrong! It is far more common to have a 30 amp overheat than a 50 amp. Now, if you are using a full 50 amps, and there is a brownout, you may be in trouble, and you should be using some sort of protection to avoid burning out AC compressors and or expensive electronics! But a 30 amp RV plugged into a 50 amp circuit, would have more of a cushion than a 50 amp, not to say an isolation transformer or some other protection should be avoided.

Wow! Please go take a basic course on electric wiring. Hopefully everyone reading your posts will have a laugh and then disregard them, as you seem to know absolutely nothing about even the most basic aspects of electric wiring!:R

Old-Biscuit wrote:

Me Again wrote:
Just remember that you will have a 50 breaker feeding #10 30amp rated cable, so if you have a problem ahead of the trailers 30 main breaker, you could have an electrical fire risk. Chris

But you can only draw 30A regardless of 50A service.....cause over 30A trailer main 30A breaker will trip and no more amp draw

Course what if.....50a receptacle shorted, or plug broke off or tree falls on power pedestal or squirrel chews on cord

.......or the sky falls!!..:R

.

10 GA and 8 GA wire are irrelevant for this conversation because the feeders for peds in an RV park are probably 1/4 to 1/2 mile long. The 10ga and 8 GA standards are for runs under 50 feet, found in a residential situation.

EDIT: Peds are fed with commercial feeder wire equivalent to the drop feeding your home or larger.