50 amp service - help

[RustyJC]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ed Gardiser:
RustyJC
Not wanting to stir the pot but your explanation of amperes and phase is not quite how it really is. </div></BLOCKQUOTE>Please see the attached which I believe is consistent with my explanation.

RV 120/240VAC 50A circuit.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ed Gardiser:
You do not take single phase power and make it 180 degrees out?impossible. </div></BLOCKQUOTE>
It's done every day with a center-tap transformer, which is what feeds the wiring schematic diagrammed in the attachment above. See the example of a center-tap transformer and the resultant waveforms (180 degrees out of phase) below - note that this transformer has a single phase input.



Rusty

[Ed Gardiser]

RustyJc
Where in that web site does it say "anything" like you're explanation of electricity !
Ed

[Bob Hatch]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Ed Gardiser:
RustyJc
Where in that web site does it say "anything" like you're explanation of electricity !
Ed </div></BLOCKQUOTE>

It doesn't, but this one does.

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

Rusty is in fact, correct. The normal power used throughout most of North America is 3-wire, single-phase, mid-point neutral system. It's what is used in your house, office, garage, laundry, and most every place you use electric service.

It is more accurate to state that the hot legs are out of phase with neutral, but it is single phase, never the less.

[RustyJC]

Thanks, Bob. Yes, the terminology is confusing - how can "single phase" power have the 2 hot legs 180 degrees out of phase with respect to each other when both are referenced to neutral? Nevertheless, the fact that they are 180 degrees out of phase is the reason that the hot legs show 240VAC with respect to each other but 120VAC with respect to neutral (ground).

The important factor insofar as us RVers are concerned is to ensure that the 240VAC potential between the hot legs is present at the 50 amp shore power recepticle. If not, and if both hot legs show 120VAC with respect to neutral, then the pedestal is wired incorrectly and neutral conductor overloads can result.

Rusty

[RustyJC]

Here's yet another explanation:

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Single phase electric power

The generation of AC electric power is commonly three phase, in which the waveforms of three supply conductors are offset from one another by 120?. The design of the power generators has three sets of coils placed 120 degrees apart rotating in a magnetic field. This creates three separate sine waves of electricity that are displaced from each other in time by 120 degrees of rotation (1/3 of a circle). Standard frequencies of rotation are either 50 Hertz (cycles per second) in Europe or 60 Hertz in North America. The voltage across any pair of these three conductors, or between a single conductor and ground (in a grounded system) is what is known as "single phase" electric power. Single phase power is what is commonly available to residential and light-commercial consumers in most distribution power grids. In North America, the single phase that is supplied is developed across a transformer coil at the utility pole (for aerial drop) or transformer pad (for underground) distribution. This single coil is center tapped and the tap is grounded to develop two waveforms that are 180 degrees out of phase with each other with 1/2 the voltage. This then creates a 120/240 volt system that is delivered to the customer. The voltage from either side of the coil to the center tap (ground) is 120 volts whereas the voltage between the the two conductors on either end of the coil develops the full voltage of 240 volts. </div></BLOCKQUOTE>

Rusty

[Bob Hatch]

Thanks for the additional links.

I've been arguing this point on newsgroups and forums now for over 5 years. Folks still want to make RV electric something different than what they see everywhere else. I had one guy on another forum insist that the breaker box in an RV was built so that you could not install a double pole breaker. On the same thread another one insisted that the bus bar was what he called a "split bus bar", with one leg going to the right of center, and the other to the left.

Because of my web site with the conversion pages I've gotten some darn fool emails. One guy, who claimed to be an EE, told me that I was totally wrong on the setup because the RV electric system was limited to the output of the generator. Another recent email told me it was foolish to use a tied breaker for the 50 amp input, because after all it was really only 2, 120 volt lines.

I still have guys that insist that a 50 amp service is a 30 and 20. 30 for the coach and 20 for the rear AC.

It's always fun to educate.

[DriVer]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bob Hatch:
I still have guys that insist that a 50 amp service is a 30 and 20. 30 for the coach and 20 for the rear AC. </div></BLOCKQUOTE>ROFLMAO

Sufficiently advanced technology is indistinguishable from magic. This is why folks can't comprehend electricity and keep guessing, estimating and ultimately have a general misconception about what's happening in their RV electric system.

When you go to the dealership and have the choice between a 30 amp service or a 50 amp service don't forget that the 50 amp service is actually a 100 Amp service. They don't bother telling you that, why, because they don't know any better than most RV buyers.

When given the choice - go "Fifty!"

[Route 66]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I've been arguing this point on newsgroups and forums now for over 5 years. Folks still want to make RV electric something different than what they see everywhere else. </div></BLOCKQUOTE>

You're right Bob, but I don't know which topic causes more confusion, discussion and cussin'; RV electricity (especially 50A), holding tank treatments (or the lack thereof), or toad supplemental brakes. :-)

I believe the fellow posting about the breaker box has that type in his rig.

[Don (W5IT)]

Does not confuse me in the least.......

Of course I have worked for utility/power companys for the last 29 years.

Let's not confuse folks and start talking about takin a three phase feed to a distribution center Lets at say a lowly 7.6 kv. Then splittin it into three single phase feeds with a transformer to feed other transformers at single phase and balance the loads within the park.

[Bob Hatch]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Route 66:

I believe the fellow posting about the breaker box has that type in his rig. </div></BLOCKQUOTE>

Well could be, but my doubter is in full swing on this subject.

How would you build a breaker box that knows the difference between a 240 volt breaker, and a 120 volt one? Go the the store, look at the the 120's, and the 240's. Hold 2, 120's together so that you can look at the backs of them. Pick up a 240 of the same brand/type, and hold it up in the other hand, and convince yourself that it's possible to build a box that knows the difference.

Even if you have a 120 volt breaker box, you can still install a 240 volt breaker, it just won't work as a 240 volt, because you only have 1 bus bar, but you can still install the 240, double pole. The 240 is really nothing more than 2, 120's connected together, with a bar to tie the switches together. In some cases it has a single switch that's tied internally, but it's still really nothing more than 2, 120's.

Now, I'm always willing to be proved wrong, and learn on any subject, so links and pictures as proof are appreciated.

[Bob Hatch]

Don, while I was in Carlsbad last year I watched a company do something similar in the RV park I was staying in. They ripped out all the old, jury rigged boxes on the side of a building and put in a whole new distribution center for the RV park. Everything from the transformer down to the point where the park feeds connected was new.

It was like watching artists paint.

[TJM]

From a woman's point of view, GO WITH 50 AMP! We paid for the upgrade from 30 amp to 50 amp when we ordered our motorhome. The best thing about having 50 amp is that it will run almost everything you can turn on in your motorhome.

I also agree with having a good surge protector. We learned the hard way by getting our convertor fried in May. Luckily that was all that was damaged. Of course, the campground 'electrician' said it happened because of arcing caused by our coach. Funny though, they replaced the entire electrical in the post. We now have a SurgeGuard protector.
Joy

[adj]

This single coil is center tapped and the tap is grounded to develop two waveforms that are 180 degrees out of phase with each other with 1/2 the voltage. This then creates a 120/240 volt system that is delivered to the customer. The voltage from either side of the coil to the center tap (ground) is 120 volts whereas the voltage between the the two conductors on either end of the coil develops the full voltage of 240 volts.[/b][/QUOTE]

Rusty[/QUOTE]

If you take the center tap out you still have 240V single phase.

[RustyJC]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by adj:
If you take the center tap out you still have 240V single phase. </div></BLOCKQUOTE>
The center tap is the grounded neutral. It's present in the feed to your house as well as the feed to the RV shore power pedestal, so I don't understand the point you're trying to make.

We're discussing real world applications, and the 120/240VAC application in question (50 amp RV service) utilizes a center tap to provide the grounded neutral as per the multiple cites and references that have been provided. Why confuse the issue with theoreticals and hypotheticals?

Rusty

[Bob Hatch]

Hey Rusty, do you ever feel like a voice crying out in the wilderness?

[Ed Gardiser]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The reason this is important is that the neutral conductor will carry current equal to the sum of the hot legs. If one hot leg is carrying 40 amps and the other 35 amps, the neutral leg current would be 40 + (-35) = 5 amps if the hot legs are 180 degrees out of phase (correct wiring) but would be 40 + (+35) = 75 amps if the hot legs are in phase (incorrect wiring). In the latter case, the neutral conductor would be overloaded. </div></BLOCKQUOTE>
Rusty
I have read the information on the other web sites which makes sence and I understand, what I continue not to understand is what was said in the above statement.
Ed Gardiser
Escondido,Ca.
04 Vectra
87 Nissan PickUp
FMCA

[Bob Hatch]

Ed, I'm not Rusty, but, 240 volt to the neutral is subtractive. 120 is additive.

The reason you can use a 6/3 wire on 50 amp 240 is because of the above. All wires are 6 guage, including the neutral. Because of the phase difference in the 2 legs, if you have an equal load on each leg, the return on the neutral is zero. So, like Rusty said, if you load 1 leg to 40 amps, and the second to 35 amps, the return on the neutral is 5 amps.

On the other side, the additive nature, if each leg was from the same side, you would continue to add return to the neutral until you burned it. Put 15 amps load on, 15 amps goes back across the neutral. Add 20 amp AC, and 35 amps are fed to the neutral. Add 20 more amps, and 55 amps go across the neutral.

Clear as mud?

[Ed Gardiser]

Bob
I agree
Clear as mud
Ed Gardiser

[AKO]

Not wanting to stir the pot.........Ahh, no one is going to believe that......
Anyway, Rusty & Bob, you need to realize that perhaps many of the posts come from people who are products of the USA public education system. As such, almost none of them have any concept of negative numbers (How the heck can somethin be less than nuttin??), sine waves (Is degrees of SIN some kinda religious thing?), or arithmetic (multiplying two negatives and coming up with something positive, just makes no sense).

So, just keep telling it like it is, but just remember most of us will...continue not to understand.

Well, I'm off to stick my finger in a light socket (get a little charge before bedtime).

[ruppr]

Rusty/Bob
As a ole retired 'Sparky' I know of what you speak. Maybe some will realize that some of us went to a 4 year trade school or college to learn this for a career.

Not putting anyone down , but sometimes it's not so simple as one believes!

Best to all,