electric service

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janpaul

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If a trailer has a 50 amp service plug, can you also install a 30 amp plug to use at sites that do not have a 50?
 

Karl

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There are 'dogbones', short lengths of power cable with different plugs and receptacles on each end, that make it easy to plug a 50A cord into a 30A outlet, 30A into 50A, 50 into 20A, ... etc. Available at any RV store and some Wal-Mart's.
 

Ned

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No problem.  You need a 30A male to 50A female adapter, available from any RV supply store.  Of course, you won't be able to use more than 30A of AC at one time, so some power management will be necessary.
 

Shayne

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They run from about 20 bucks to 29 bucks.  Even available at Wally World.
 

John From Detroit

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Rigs come in several sizes.. Here is a guidline

Only one Air Conditioner,, Generally 30 amps is all you need

Two AC's need 50 amp 

50 amp service to an rv is really 100 amps divided (But you only need 50)

"All Electric" (Electric range, hot water electric only, fridge electric only) you need the full 50 amp and may even need 100 (Really 200 divided).  Those rigs are, far as I know, rare

I run my rig off 20 amps most of the time (it's a 30 amp outlet but a 20 amp breaker) 30-50 when on the road though
 

2006F350

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Since my fiver is wired for a second A/C, it has 50A service, but presently, we only have 1 A/C. The norm for me is when reserving a site, is that I request 30A service as it's usually a few bucks cheaper. I'm not really a cheapskate, but if I don't need the extra capacity, why should I pay for it. The only time I had a problem was at one park, when the A/C kicked while the microwave was running, it tripped. At the same time, the resort owners happened to be out, and we had a small chat as they saw me out looking over the box. They determined that the problem was a weak circuit breaker, and said they would have it changed, which they did. Took care of the issue. In the process, talking with the electrician, he told me that everytime a circuit breaker trips, it's rated capacity actually decreases by 2 to 3 amps, so if it had tripped 5 times, that 30A breaker could actually only hold a load of 15 to 20 Amps before tripping. It's surprising what you can learn by being 'curious' when the pro's are at work.

Larry

 

Ned

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everytime a circuit breaker trips, it's rated capacity actually decreases by 2 to 3 amps

If that were true, there wouldn't be any power in any campground.  As an electrician, that guy would make a good ditch digger :)
 

Karl

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Larry,

I find it hard to believe that. Circuit breakers do get weaker with abuse, and that's what you find in a campground. People switch off the breaker without removing large loads first when leaving. Regular QO c.b.'s are rated HACR, meaning they are UL tested and approved for heating, air conditioning, and refrigeration loads (i.e. motors), and have arc quenching built into them, but they are not meant to be used as switches. For highly inductive loads, special c.b.s are available that will fit in a regular distribution center. 2-3 Amps degradation per trip is totally bogus.   
 

2006F350

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He may have said milliamps, it's been quite awhile, and one of the signs of getting old is that you only hear / remember what you want. One thing though, should have clarified it .. 'tripping' as in overloading (Karls word: Abuse). He wasn't refering to using it as a switch - heck, I do that all the time, and it does not have any appreciable effect other than "killing the juice" instead of me ... I have been told the same by more than one electrician concerning degradation each time it trips because of an 'abuse' condition.

Larry
 

Karl

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Janpaul,
A lot of circuit breakers have the designation  SWD on them which means they are rated for switching.
Quite true, however Square D specifically states that they are suitable for fluorescent lighting loads; no mention is made about high current/high inductance loads like motors. Maybe they can handle it, but my GUESS is that it pertains to the high voltages present in fluorescent circuits. I would check with the mfg. and get their advice about using them for things like a/c. Of course, if the a/c isn't running, it doesn't make any difference. :)
 

janpaul

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Breakers are fine for motor branch circuit protection as long as they are sized properly. I don't know how familiar you are with it, but the NEC article 430 has all the sizing guidelines and regulations for the protection and installation of electric motors. Most motor control centers have "buckets" that contain the breaker, starter, controls, etc, but that is more in industrial installations.
 

Karl

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Janpaul,
I'm not sure where you're going with this. You started by asking a simple question about hooking up a 50A plug to a 30A outlet, and now we're in the middle of NEC's (430 specifically) which has nothing to do with c.b.'s in motor homes; manufacturing and industrial applications only. The NEC's are so ambiguous as to confuse even an expert EE, that I can't see how any of that pertains. Maybe you can straighten me out?
 

janpaul

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I wasn't going antwhere with it, the discussion went to breakers and I was just trying to provide a little info on the subject. Sorry if I got off course, I tend to do that when it comes to the electrical field, after 21 years in the trade. If anyone here ever needs help or advice on electrical , NEC etc, I would be glad to put my .02cents in if able. A guy who trained me always said "knowledge isn't just knowing the answers, it's also knowing where to find them if you don't".
 

John From Detroit

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I will thrid that Karl, if you have a good library, and know how to use it then you know everything (not many folks have quite that good a library, though the Library of Congress comes close)  It is possible to know everything about ___<fill in subject>___)

As for how we got to where we got.

Thread drift of course, don't you know it is THE LAW of the internet? :)
 
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