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Old 07-28-2013, 04:46 PM   #15
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Originally Posted by gemini5362 View Post
I hope I misunderstand your post. You said you have a 30 amp motorhome. do you have a 30 amp cable with a 30 amp male end for the shore pedestal. Do you then take a 50 amp male adapter which you plug into the 50 amp shore pedestal. Does this 50 amp male adapter plugged into the 50 amp shore pedestal have a 30 amp female on it which you plug your 30 amp cable from the coach into. I hope I have that explained clearly. In simpler terms is the cable from your coach rated at 30 amps and is it plugged into a 50 amp receptacle with 50 amp breakers. If this is what you have it is extremely dangerous and you would be a major candidate for a fire somewhere in your coach.
I said the same thing on this forum several months ago, and was corrected by many, that this is standard procedure with 30A coahes connected to 50A pedestals .
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Old 07-28-2013, 04:54 PM   #16
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Originally Posted by gemini5362 View Post
I hope I misunderstand your post. You said you have a 30 amp motorhome. do you have a 30 amp cable with a 30 amp male end for the shore pedestal. Do you then take a 50 amp male adapter which you plug into the 50 amp shore pedestal. Does this 50 amp male adapter plugged into the 50 amp shore pedestal have a 30 amp female on it which you plug your 30 amp cable from the coach into. I hope I have that explained clearly. In simpler terms is the cable from your coach rated at 30 amps and is it plugged into a 50 amp receptacle with 50 amp breakers. If this is what you have it is extremely dangerous and you would be a major candidate for a fire somewhere in your coach.
Yes, that's exactly what I said.. so I don't know why you're trying to explain it in even more complicated terms.

I'm not at anymore risk for fire than if I was plugged into a 30A receptacle unless I was stupid and tried to run two or three 1500W electric heaters at the same time. I am running as much electricity through the system as a 30A system allows.

Unless I try to pull over 30A, I'm not at any risk for fire. Outlets push VOLTAGE out through the cord, but not AMPERAGE without a load on it. An appliance has to demand amps/watts before cords begin to heat up. Idle or under utilized circuits generate don't catch fire unless there is some kind of a short, then it's a fire hazard no matter what.

You could plug a 100ft 16 gauge 120v outdoor cord into a 50A outlet with adapters and there would NEVER be a fire, even if you left it that way for 20 years. Assuming you don't try to pull more than a few amps through it that is! If you try to pull more amps through it than it's designed for, then you have problems.

So no, simply having it plugged into a 50A outlet is not a fire hazard. Overloading the van's electrical system beyond 30A with appliances, tools, electronics, whatever else... would be.

Which goes back to the original post... it sounds like they tried to pull more than 30 amps through a 30A cord and adapter which is a big no-no! They overloaded their cord. I am not overloading anything. I am using my van's electrical system exactly within the specifications it was designed to be used.

The closest I might come to this is using a 20A to 30A adapter. In which case, the fire hazard would be outside at the pedestal since the adapter or outlet is what would become overloaded, not my van's electrical system.

Oh, and I have two fire extinguishers so far. One inside the van, one outside in a compartment. I will be getting a second for the interior at the bed.
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Old 07-28-2013, 05:24 PM   #17
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Pusherman;

I also would like to thank you for taking the time to post the pictures and the expert advice. This brings up another question to my mind. I have a 50 Amp Portable Surge Guard locked to the plug on my power cord. I would have installed the 50 amp to 30 amp adapter between my Surge Guard and the pedestal. Do you think the Surge Guard would have sensed a problem and shut down the power before a fire broke out? We had a lightning storm one time that burned out the coil on the transfer switch and that is when I purchased a Surge Guard.

I also am happy nobody was hurt.

Don
Don, I do exactly as you do, having a surge guard at the end of the 50A shore cord, and if necessary, adapted down to 30A at a 30A source. I think that's good practice.

Surge Guards shut down the power if there is reverse polarity, low voltage, high voltage, and surges. So it may have helped in this situation, depending on the exact failure mechanism.

The pedestal was protected by a 30A breaker. It was a relatively new service. I could not verify if the breaker tripped, as it was inside the fire-line tape border.

This incident occurred before we arrived. I respected the fire-tape border, and did not go inside this line to closely inspect the dog-bone adapter.

First glance the dog-bone adapter was a stock Camco 30-50A adapter with the yellow plugs with handles. I don't know if it was modified or not. One thing complicating the picture I posted, is that a TV cable wire is also in the picture with the adapter. This melted as well, and is somewhat jumbled up with the dog-bone adapter.

I was told by the sheriff deputy who helped out that the Fire Inspector also thought the fire was caused by the dog-bone adapter. Don't know if it was modified.

I'm not trying to prove a failure mechanism, but offer some common sense suggestion to help prevent such an incident in the future.
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Old 07-28-2013, 05:35 PM   #18
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Cubey - I guess I am a little confused too.

If you are a 30amp connection and plugging into one leg of a 50amp supply then you are not protecting your circuits at the pedestal - that is a 50amp circuit breaker but your plug and cable are only rated at 30amps.

See the problem?
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Old 07-28-2013, 05:44 PM   #19
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However, the RV has a 30 amp breaker, so you cannot draw more than 30 amps.

Quote:
Originally Posted by steveclv View Post
Cubey - I guess I am a little confused too.

If you are a 30amp connection and plugging into one leg of a 50amp supply then you are not protecting your circuits at the pedestal - that is a 50amp circuit breaker but your plug and cable are only rated at 30amps.

See the problem?
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Old 07-28-2013, 05:45 PM   #20
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Cubey - I guess I am a little confused too.

If you are a 30amp connection and plugging into one leg of a 50amp supply then you are not protecting your circuits at the pedestal - that is a 50amp circuit breaker but your plug and cable are only rated at 30amps.

See the problem?
I see the point you are making, but again, I would have to be pulling more than 30A before it's a problem. I ran this van extensively on a 15A outlet in a house with a 20A (I forget which). The only time it ever tripped the breaker was when I ran a full size washing machine in the house on the same circuit and it tripped the breaker when it got to the spin cycle.

Unless I pull over 30A, nothing is being overloaded. Seeing as how my only big power draw is my A/C (and a dorm fridge's startup amps, it has low constant draw) both of which I ran extensively on a 20A breaker with no problems at all .. except save for the washer incident that one time which I clearly don't have now in an RV park.

I suppose I could play it safe and use the 15/20A outlets on the pedestal but that's a greater fire risk than what I have plugged in now. Three and a half weeks now on this 50A hookup and no problems what so ever. But I use my noggin and don't do stupid things. I understand electrical system limitations which is more than most people.

Safety is about using common sense in all that you do.
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Old 07-28-2013, 05:54 PM   #21
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However, the RV has a 30 amp breaker, so you cannot draw more than 30 amps.
That is a very good point. The main breaker INSIDE the van is 30A. I didn't think about that until you pointed it out.

It's odd actually, the sub-breakers are all 30A as well which seems like a bad idea. They should probably be 20A probably except the dedicated circuit for AC and water heater (which has a switch so only one or the other can be powered, not both at once). Although, I doubt the AC pulls more than 15-20A startup. The water heater is only 1000W so that's about 10 amps so I could probably have them on a 20A breaker. But since it's dedicated to them it doesn't matter, I can't add to it. Now on the other circuits for outlets, those should be 20A in my opinion simply due to the wiring leading to the outlets which are probably rated to 20A.

But lets say I was dumb and tried to pull 25A on two different circuits at the same time. Since they are each 30A breakers, they wouldn't trip. BUT, the main breaker WOULD trip since it would be trying to pull 50A through a 30A breaker.
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Old 07-28-2013, 05:59 PM   #22
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An adapter cannot just shortcut for no reason. The most common reason for these type failures is dirty or corroded connectors in the adapter or the blades of the plug. This bad connection causes resistance which in turn increases te current draw across it so it acts like a heater element and heats up the plug or adapter until it melts and then shorts out. You can easily check for this problem by feeling the plug and adapter. If the are hot then time to replace the adapter and polish the blades on the plug with a Scotchbrite pad until they shine. This is the same cause of fires in circuit breaker boxes if the wire connections are loose. If all the onnections are clean then the circuit breaker on the pedestal will stop current overload. Contrary to wives tales circuit breakers normally do not fail and the fault or fire is caused by bad, loose or dirty connections.
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Old 07-28-2013, 06:14 PM   #23
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Yes, they kept the 50A shore cord coiled in the electrical bay, adapted it with the dog-bone inside the electrical bay.

One of the very first things they taught me was to NEVER EVER coil an "In use" power cord. always pull it out you can snake it (Back and forth) but NEVER coil it.

I tested the theory.. I pulled about five amps through a coiled up 12ga cord.. That is a fraction of the rating (20 amps) of such a cord) and that coil got uncomfortably (not dangerously thankfully) hot.

I should point out that the use of this cord was kind of a 9-1-1 situation.. (It powered a couple of 9-1-1 work stations because I had the needed cords and the idiots who wired the office only put on workstation on the E-Panel (Generator powered))

Thus I always pull the cords out and if needed snake 'em. Never coil them less they are unplugged.
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Old 07-28-2013, 06:17 PM   #24
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An adapter cannot just shortcut for no reason. The most common reason for these type failures is dirty or corroded connectors in the adapter or the blades of the plug. This bad connection causes resistance which in turn increases te current draw across it so it acts like a heater element and heats up the plug or adapter until it melts and then shorts out. You can easily check for this problem by feeling the plug and adapter. If the are hot then time to replace the adapter and polish the blades on the plug with a Scotchbrite pad until they shine. This is the same cause of fires in circuit breaker boxes if the wire connections are loose. If all the onnections are clean then the circuit breaker on the pedestal will stop current overload. Contrary to wives tales circuit breakers normally do not fail and the fault or fire is caused by bad, loose or dirty connections.
Mike, I agree.

I have had 2 coaches with 30A services, and both of them needed new plugs on the end of the shore cord, as the molded plugs would melt around one of the prongs due to resistance, causing more heat build-up, which would just make things worse.

Thus the advice. Get a new 30-50A adapter every couple years, keeping the 30A side of the plug in good shape. Keep your shore cords short as possible - also building up less resistance and heat.
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Old 07-28-2013, 06:26 PM   #25
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Cubey - I guess I am a little confused too.

If you are a 30amp connection and plugging into one leg of a 50amp supply then you are not protecting your circuits at the pedestal - that is a 50amp circuit breaker but your plug and cable are only rated at 30amps.

See the problem?
A 50A coach on a 30A supply can be a problem because of the potential to overload. I have to be cognizant of the loads I am using when I am on 30A, even though the 30A breaker at the pedestal 'should' pop if I exceed 30A.

A 30A coach on a 50A supply is not a problem because the coach cannot (easily) overload the supply.

A 50A supply for a 30A coach can be thought of as having 'up to' 50A available for use, which a 30A coach should never approach under normal circumstances. The 30A coach cannot present enough load to cause problems because its own 30A main breaker 'should' prevent it.
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Old 07-28-2013, 06:44 PM   #26
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I am glad that the folks with the fire didn't lose everything.

About the power discussion. Just to add a bit more confusion to the issue in order to make things 'perfectly clear'... 50A service uses L1, L2, Neutral and Ground. The voltage across L1 & 2 should be around 240V. From L1 or L2 to N or G should be around 120V. Each L is supplied with a 50A breaker packaged to both trip if one leg goes to overcurrent.

If the N goes open for any reason the full 240V is applied to the RV service panel and expensive things then happen. The G is for safety so that the frame of the rig won't get 'hot' if a live wire should short to it. The breaker, in theory, should trip.

On a 30A service only the L1 is hot, so between L1 and N or G you will see around 120V. If you lose the N you simply have things that don't work or act 'weird'. But, if somehow N finds its way to L2 bad, very bad things happen!

My work for the phone company in power taught me a few thing. The associate deg in electronics might have a bit of influence too. But, in any case, even the experienced can blunder. So far mine have not caused any great problems. Functional circuit breakers are a great friend.

May you pedestal always be your friend.

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Old 07-28-2013, 07:00 PM   #27
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I know what you are saying regarding the 30amp breakers inside the coach and I am sure it will never become an issue.
However it is completely against 'code' in an electrical system so as long as you are aware of the 'potential' (sorry for the pun LOL) problems then I am sure it will be OK.
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Old 07-28-2013, 07:00 PM   #28
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A 50A coach on a 30A supply can be a problem because the potential to overload is high. I have to be cognizant of the loads I am using when I am on 30A, even though the 30A breaker at the pedestal 'should' pop if I exceed 30A.

A 30A coach on a 50A supply is not a problem because the coach cannot (easily) overload the supply.

A 50A supply for a 30A coach can be thought of as having 'up to' 50A available for use, which a 30A coach should never approach under normal circumstances. The 30A coach cannot present enough load to cause problems because its own 30A main breaker 'should' prevent it.
-----------------------------------------------
This is what I'm getting out of this. The coach knows it can handle 50A. It will allow more than 30A be be used? Therein lies the "danger" when only 30A is available?

That being said, the pedestal 30A breaker SHOULD HAVE tripped when the demand got to be too high?

I have a 30A coach so I would not have THAT problem? That being said, I am immediately:

#1 Headed out to uncoil my cord.

#2 Ordering a NEW 50A to 30A adapter for future use if needed. (Not going to rely on the one that came from the PO)

#3 Ordering a surge/overload protector.
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