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Old 06-25-2010, 01:40 PM   #15
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Great post Paul. The only thing I would add is that I have found some 30 amp breakers that have seen better days and trip to soon due to age and or abuse. If this is the case I will not hesitate to use my adapter to move over to the 50amp outlet.
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Old 06-25-2010, 02:30 PM   #16
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FWIW Here we go again, sorry. Paul, thank you for the great description. Question; If several units were plugged in at the a park 50 amp the way the OP suggested, all with the same brand of 50 to 30 Bone, would this unbalance the one leg, phase, in the park? Obviously we are assuming everyone is running the A/C at maximum. Also, on the pedestals with both 30 and 50 outlets does the park alternate the 30 amp from phase to phase to try to balance the system?
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Old 06-25-2010, 03:36 PM   #17
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FWIW Here we go again, sorry. Paul, thank you for the great description. Question; If several units were plugged in at the a park 50 amp the way the OP suggested, all with the same brand of 50 to 30 Bone, would this unbalance the one leg, phase, in the park? Obviously we are assuming everyone is running the A/C at maximum. Also, on the pedestals with both 30 and 50 outlets does the park alternate the 30 amp from phase to phase to try to balance the system?
I suppose all the dog bones could conceivably be wired the same and all the 50 amp legs could be pulled down on voltage on one end of the park but that alone is a very long shot. Even if they weren't using a dog bone and were all plugged into the standard 30 amp plug the park would be in a brown out... It's customary to wire phases to receptacles differently depending on the quantity of panels in the park. All this also assumes that the electrician used wired them that way and that there is not a large enough power supply to start with. If wiring using current electrical codes and supply is adequate at the main feeds, you should never see a brown out in a park. But, as we all know many parks were built many years ago and are woefully under supplied. Experience suggests that these parks that suffer brown outs are old and rarely even offer a 50 amp receptacle. Those campgrounds really do suffer power problems. My trailer has a 50 amp drop cord and is wired just as I stated in the above post. More often then not, I don't have a 50 amp plug to access in most campgrounds. I have to use a 30 amp receptacle to a 50 amp drop cord. I'm always having trouble. But, I have a newer coach and use older campgrounds or ones that have not yet been upgraded. Wiring a campground is exceedingly expensive because it's mostly underground and based on the # of pedestals, the feed units are large and expensive. So, older campgrounds rarely upgrade. In that regard, plugging into a 50 amp receptacle would be of benefit simply because it suggests a newer wiring scheme because it actually contains 50 amp receptacles.
-Paul R. Haller-
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Old 06-25-2010, 04:17 PM   #18
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Thank you Paul for taking the time to answer so eloquently and quickly.
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Old 06-25-2010, 04:33 PM   #19
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Originally Posted by Dmiles View Post
My MH uses 30 amp service. I bought a 30 to 50 amp adapter for those times when I'm at a CG where 50 amp is all that is available (it has happened twice).

Got me to thinking, why not just use 50 amp service whenever it's available? I would be assured better quality power, and everything in my MH is protected with breakers, so, why not?

Anyone have any ideas on why I shouldn't do this?
Well, I do have an idea

And that idea is "There is nothing wrong with your thinking"

As for why you should not do it... The puriest will likely complain that the 30 amp cord on your RV is not big enough to handle the same load as the 50 amp breaker.. And if just the right conditions exist a fire could result.

And he's right, JUST the right conditions (I'd give the odds as one in several billion) would have to exist, Not a dead short (Which will trip the 50 amp breaker before anything bad happens) but a partial short. Almost impossible.. In fact I've never heard of it happening and do not expect to.

Oh, as for a simple overload.. the 30 amp main breaker in your unit will take care of that, protecting both the unit and the extension cord/power cord.

So there is no reason.. and you are quite right the power may be better (less voltage drop) on the 50 amp outlet
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Old 06-25-2010, 07:12 PM   #20
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Pigman Please confirm the following to see if I get this right.
The OP is connecting his 30 amp to a 50 amp protected service. This would be to just one side of the 50 amp service. And, as you stated no 30 amp protection would be provided. This is Not the 30 to 50 amp bone, it is a 50 to 30 amp bone.

This would be okay if only a 50 amp receptical were present but if a 30 amp were there, that one should be used because the pedestal would provide the protection.

The 50 amp would not be able to provide more than 30 amps within the unit because the unit's system would limit itself to 30 amps?
Yep, you got it. The 50-30 bone cuts off one leg so the only thing he'll have will be a hot, ground, and neutral. 120V no matter where you measure it.

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Old 06-25-2010, 09:02 PM   #21
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I want to thank everyone, and I do mean everyone for their replies. Thank you Paul for taking the time out to post such useful and well laid out information. I do appreciate it.

Mudpuppy, you must have some kind of ESP. The thing that got me started on this is that I camp at a lake specifically for scuba divers. They only have 6 (really 5, but they have 6 they call rv sites) that are big enough for RVs, but they do have 30 and 50 amp power.

One hot saturday after the AC had been running all day, the 30 amp breaker tripped. When I went to reset it, she was hot as a firecracker, and the way it felt when I reset it didn't give me a warm and fuzzy at all. I could tell the 50 amp power had been added, and was on its own circuit, with what looked like at least #6 wire. Given the fact that the 50 amp breaker had probably only rarely been used, I opted for the adapter, and felt much better.

So, I guess I'll just be taking it on a case by case basis, but whether your rig is rigged for 50 or 30, an adapter to be able to plug into the "other" power if needed is probably not a bad thing to carry.
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Old 06-25-2010, 10:08 PM   #22
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I have stayed in CG where the 30a receptacle is badly worn but the 50a is like new. I use a dogbone adapter 50a-30a. Never had a problem.
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Old 06-26-2010, 03:40 AM   #23
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If the original poster has a 30 amp cable that's wired for a 30 amp receptacle but has access only to a 50 amp pedastal. A cheater cord made expressly for that application can be used. A little background is needed here though for a through understanding of what's happening when you use a 30 to 50 amp adapter.

Firstly, a 30 amp receptacle has a single phase of 110 power, a neutral , and a ground supplying the 110 volts through a single phase with a breaker set not to exceed 30 amps. In a 50 amp receptacle the pedastal is wired with 2 phases of 110 (Directly opposite each other) a neutral, and a ground. Each leg of the 2 phases is set with a breaker not to exceed 50 amps each. So in direct comparison, a 30 amp receptacle can deliver only 30 amps of a single phase. A 50 amp receptacle can deliver 50 amps on each leg of 110 delivering a total of 100amps on two phases.

When you use an adapter thats designed to use a 30 amp plug to a 50 amp plug it completely ignores one leg of the 2 110 phases and delivers one 50 amp leg to the hot side of the 30 amp cord. It also connects the grounds and neutrals together normally. So, now you are getting one 50 amp leg of power to your 30 amp cord, a neutral, and a ground. Your coach 30 amp main breaker becomes the safety valve for not pulling too much amperage through the cord. I suppose if the original 30 amp cord develops a short before the main breaker in the coach, you could overheat the 30 amp cord but that is unlikely.

The 2 phases of 110 can be connected to each other to produce 220 also but that is never done in any coach wiring I have ever seen. The 110 loads are split up among the 2 110 phases so you only have 110 at any given time. All the draws return to the pedastal through the neutral. The huge difference between 50 amp 110 and 30 amp 110 comes directly from the 50 amp recptacles offering 50 amps of 110 power on each leg giving a total power of 100 amps instead of 30amps total on one leg of a 30 amp system. That's more then 3 times worth of power available. The breakers on a coach wired for 50 amp have 2 mains one for each leg supplying power. On a 30 amp system the coach has a single breaker rated at 30 amps because it only uses one leg to get power through. The cable supplying power to the coaches are also different.

In a 50 amp system the cable will have 4 conductors of either #8 or # 6 wire to supply both phases of 110 , the neutral and ground. Sometimes the ground wire is a # 10 because it's used only as a safety and no current should be flowing under normal conditions through ground. A 30 amp system uses a 3 wire cable of #10 wire. One conductor for 1 leg of 110, a neutral, and a ground. The 50 amp sysem uses larger wire because you can draw more current through it.

Is the 50 amp system better power? As stated above, the power all comes from the same system so, no, it's not better, it's the same. There is more power available but it's limited by the coaches 30 amp breaker. My assessment is that it probably makes little difference when a brown out occurs which amp system, plug, or pedestal is used. Brown outs occur from too much draw on a system at any given time dropping voltage on any phase below 110 volts. When this happens motors and compressors found in coaches draw more power to start and keep running anything because voltage is low. Remember Ohms law that states simply that lower voltage = more current draw.

In conclusion, it 's OK to use a cheater cord to access the 50 amp receptacle when your coach is wired with a 30 amp drop cable and it's probably safe. Is it better? Not really.
-Paul R. Haller-
I would have to offer, that in some situations, a 50 amp supply under certain lower voltage scenarios, will have less voltage drop. This is due to the larger gage wiring to the pedestal. Amperage over resistance = voltage drop. Larger gage wire = less resistance; helping the coach not to have to try and operate induction apparatuses that could be damaged by low voltage.
This is not to say, that low voltage could still be a problem but it just depends on how low it gets on the entire local grid. If marginal it could be a plus.
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Old 06-27-2010, 06:31 PM   #24
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I've seen pedestals where the 30A outlet suffered from low voltage. Use of the 50A outlet on the same pedestal might alleviate that. I say "might", because it depends on how the pedestal is wired.
In any case, there is no harm in using the 50A outlet and an adapter. The worst "risk" is that the shore power cord does not have the protection of a 30A breaker. Hardly worth mentioning, in my book.
At this year RV show I pick up a 50amp to 30amp adapter thinking some day it might come in handy.

Well, on my last trip we pulled into a campground on a Friday were most of the campground loop was filling up. The State Park had just installed new 50 amp service to the area of the campground the last year. The next day it was rather hot so a good deal of the RV's were running air and such. I noticed on my analog voltage meter my power was dropping 112-110-107 106....It was well into the RED zone of my meter. Once it goes below 109 I keep an eye on it. Usually the frig will kick over to gas when it gets too low.....Since my trailer has 30 amp service I thought I would try using the 50 to 30 amp adapter to see if that helped. No, same low voltage.....I just kind of watched what I ran. I noticed the voltage improved as people left on Sunday and Monday.

I had asked the camp host on Sunday who was parked across the street if his power was low. He brought over his meter and checked the power at the box to find it at about 108-109 range. The park electricians came over Monday and checked it again to find the power back up to the 118-120 range.

I'm just going to assume the power coming into the park is overloaded for it's rural location.
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Old 06-28-2010, 08:16 AM   #25
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WHEW!!! As an electrically inept RV'r, I always read, and in this case, re-read, posts having to do with issues I need to understand better....HOWEVER.....threads such as this one just leave this ol head a spinning !!

I sometimes get to thinkin that folks who "can" and "do" work on the more complex aspects of various rigs, such as, electrical systems, power plant systems (engines), hydraulic systems, etc., have gotten together somewhere along the line and come up with a sort of secret rule...which says in effect.....anytime anyone asks for help concerning one of these topics, let's provide info that will be SO confusing, contradictory, and convuluted, that no one will ever know more after reading our helpful responses than they did before reading em.

YA THINK?? Steve

P.S. I'm just TOO old to go to Electricians School, Engine Maintenance School, and/or Hydraulics School, etc. in order to learn the CORRECT answers regarding...."how to",.....BUT I keep trying
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Old 06-28-2010, 02:59 PM   #26
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....anytime anyone asks for help concerning one of these topics, let's provide info that will be SO confusing, contradictory, and convuluted, that no one will ever know more after reading our helpful responses than they did before reading em.
Yeah, Steve, that's what I think too. Far too often, simple questions get multiple, complex answers. And for the record, I have been known to contribute tothat confusion from time to time.

But sometimes a seemingly simple question does not have a simple answer. And giving a simple answer where it is not appropriate might lead to a dangerous action.
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Old 06-28-2010, 06:37 PM   #27
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WHEW!!! .....anytime anyone asks for help concerning one of these topics, let's provide info that will be SO confusing, contradictory, and convuluted, that no one will ever know more after reading our helpful responses than they did before reading em.
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Yeah, Steve, that's what I think too. Far too often, simple questions get multiple, complex answers. And for the record, I have been known to contribute tothat confusion from time to time.

But sometimes a seemingly simple question does not have a simple answer. And giving a simple answer where it is not appropriate might lead to a dangerous action.
Right you are, Gary, especially when potentially lethal differences of potential are involved.

But if I may, I think I can boil this particular thread down a bit. What I take away from it is sure, using a dogbone to tap in to the 50 amp power is fine when the situation calls for it. Such as when the 30 amp breaker and/or plug has seen its better days and the 50 amp looks barely used, or if a site with 50 amp only service was all that was available that day, or any one of a few more reasons that come to mind.

So, carrying a dogbone is a good idea, and well worth the modest investment in my view. But when the 30 amp service is available, and looks to be in good order, then by all means that's what should be used by those of us who's rigs were designed to run on 30 amp service.

So, did I really boil it down, or did I add to the confusion?
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Old 06-29-2010, 09:08 AM   #28
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Sounds like a good synopsis to me!
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