Question on using 50 amp sevice

[RLS]

First, what led me to using the 50 amp service was the fact that at some SP, I was tripping the 30 amp outlet outside more than once while camping. So I figured, why not get an adapter and start using the 50 amp one where available This seamed to work till this past winter.
We were up in northern GA using a space heater most of the time for about 2 wks. I went to unplug it and found the male plug from the trailer had melted to the female adapter plug Now I'm trying to understand what caused it. The breakers inside never tripped. So why would it have a melt down at the plug? Is it that the load going through the wiring is to much for the size power cable of the trailer? or is it that the load was to much for the plug itself? Since I need to replace the plug, my thinking (I know, Bad idea) why not use a 50 amp plug and get an adapter to go to 30 amp when needed. This might solve a melt down?? Any input on this would really be great

[Dwight]

Just to clarify, your trailer is 30amp and you are connecting to a 50amp receptacle (shore power)?

try this link....http://www.airforums.com/forums/f37/...ted-57807.html

[TBRich]

I believe that if you are using an adaptor from 50 service to a 30-amp cord and circuit (your AS) that you are only getting 30 amps in the translation...I am pretty sure you are not getting more power.

It sounds to me like there was an issue with the source rather than your unit that caused the melt-down.

[Dwight]

The 50amp plug has 4 prongs. There is one ground, one neutral, and two hot wires. The Airstream should never have to be hooked up to one of these simply because the internal wiring of the Airstream is rated at only 30-amps. unless you change your breaker box.

If you use as 50-amp to 30-amp adapter, it will work just fine as long as you never attach any additional heavy load electrical items to the Airstream's duplex outlets. If you attempt to do so, the 50-amp service will be more than happy to send all that power to your vehicle but you better hope that the 30-amp breaker on the Airstream will trip otherwise you could be looking at melted wires or a vehicle fire.

[garry]

A "LOT" of power outlets at campgrounds have pitted and corroded 30 amp outlets causing resistance that in turn leads to heating at the connector eventually destroying the CG outlet and the RV plug.

Your 30amp male plug could have been pitted and had a high resistance causing excessive heat.
This is mostly caused by campers plugging in and unplugging their power cords without turning off the breaker.

Another problem is the 50amp outlet is protected by a 50 map breaker so your breaker box in the RV is the only protection from overloading and I have seen more than one wired with out the 30 amp main.

[lewster]

A 50-to-30 amp connector simply uses one of the 120VAC hot legs in the 50 amp receptacle and the neutral and ground. You don't really gain anything over the straight 30 amp outlet, and in some cases, you actually limit yourself to 25 amps.........or half of the 50 amps available.

You seem to be over-drawing the rated capacity of the wire in your shore cord, resulting in excessive heat and melting. I would add up the appliances that you are using, and I bet you are way over 30 amps (360 watts).

[withidl]

Originally Posted by garry

A "LOT" of power outlets at campgrounds have pitted and corroded 30 amp outlets causing resistance that in turn leads to heating at the connector eventually destroying the CG outlet and the RV plug.

Your 30amp male plug could have been pitted and had a high resistance causing excessive heat.
This is mostly caused by campers plugging in and unplugging their power cords without turning off the breaker.

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Agreed. I will add that you can sand (400 grit) the 30 amp connector "prongs" till they shine to remove pitting/corrosion for better contact AND inserting/removing the 30 amp connector numerous time (without load) will also remove some of the pitting/corrosion in the campsite recepticle.

[RLS]

Thanks everyone First, The trailer is set up for 30 amp service. Second,from what little I know, I think there is 50 amps going to each prong of the 50 amp service outlet, not 25 amp. This was why I started using the 50 amp in the first place. Third, the plug being pitted I guess could be the culprit. That sounds like it would cause it, not the wiring size being to small for the load. I'm sure we were at the limits of what could be used. I got a feeling what might have put it over the top for the melt down was when the electric hot water heater would kick on. Next time in cold weather like that I will be using the gas for the hot water heater.
I like how much bulk and tight fitting the 50 amp plug is, so that is what I am going to use with an adapter to go down to 30 amp service when needed. I will be using just one side of the 2 prongs. Hopefully this is OK?? Thanks again, this forum is the best

[garry]

Wrong info here........

The 220V outlet is no different than what is used in your 220 at home the difference is it is wired in the load center of the RV so you have 2 separate 120VAC sources each one at 50 amps for a total of 100 amps or 12000 watts total.

On a 30 amp RV you only have one 120VAC line from the pedestal into the RV with a 30 amp main breaker.

What you plan to do is fine you will only be using one side of the 50 amps the only down side is you have a 50 amp breaker at the CG pedestal and hopefully a 30 amp main in the RV so you can only draw 30 amps.

Running a 1500W heater =12 or 13 amps HW heater kicks on and you are now pulling around 27 amps add the converter and you are maxed out close to tripping the 30 amp breaker. Running the HW heater on gas solves the problem.

[RLS]

Garry, Thanks for the info. Here is what I was putting up to show why I thought it was 50 amp each leg.

From this common service we can draw 120 or 240 volts. Each leg is 50 amps @ 120 volts. 50-amp X 120-volt = 6000 watts. But since there are 2 HOT 120-volt legs at 6000 + 6000 = 12,000 watts to use in the RV or 50-amp X 240-volt = 12,000 watts when used as a 240-volt service.

This is for RV service. and yes, I do have a main 30 amp breaker inside plus 4 (I think) 15 amp ones.

[Jammer]

Originally Posted by RLS

We were up in northern GA using a space heater most of the time for about 2 wks. I went to unplug it and found the male plug from the trailer had melted to the female adapter plug Now I'm trying to understand what caused it.

In general, the plugs on 30 amp shore power cords eventually fail and melt even if they aren't overloaded.

This can be caused by any combination of: corroded and worn campground shore power receptacles, corrosion on the blades of the plug, or corrosion or fatigue on the clamp connection between the blades of the plug and the shore power cable.

While in theory overloading can cause it too, most plugs that fail don't fail because of an overload. You should have a 30 amp main breaker that will trip in the event of an overload. If not, add one.
Since you have a 30 amp main breaker, overloading isn't the problem, because the breaker would have tripped.

The molded-on plugs don't always last for the life of the cord. At the first sign of overheating, unless the problem is with the campground receptacle, the plug should be cut off and replaced.

[NevadaGeo]

An infrared temperature gun could tell you where the cord or plug is getting hot. I use one a lot, check the disc brake temperatures, check temperatures in the engine, check if the freezer is getting colder, lots of uses.

[Secguru]

30 Amp 120 Volt service is 3,600 Watts, not 360 Watts.

[Hodum]

There was probably a loose connection where the melting took place. The spring tension of the female plug was more than likely weak and allowed heat build up. The thirty amp adapter only connects to one leg of the 240 volt plug and that will only alow 120 volts to the main in the RV. The main will limit the amperage to 30 amps therefore under normal circumstances no problems. Usually when there is heat there is a loose connection or an overload. In this case the main 30 amp breaker in the RV would have prevented an overload.

[Secguru]

There are actually two most likely causes for the plug melting:

1) I agree with Hodum's assessment (see previous post). If the electrical system within the Airstream were drawing too much current it would trip the 30Amp Main Circuit Breaker. A loose fitting 50Amp receptacle could cause melting due to increased resistance across the connection (I=E/R - Ohm's Law).

2) Depending on the wiring, it is possible for it to supply either 30Amps or as low as 25Amps. (2 - 25 Amp 120VAC legs = 50Amps @ 240VAC). If this receptacle was wired to provide 24Amps instead of a maximum of 30Amps, and you were drawing near 30Amps, this could explain the melted plug. You can see how it is wired by looking at the 50Amp breaker. Often it will comprise two 25Amp 120VAC breakers tied together by a common metal pin.

Nonetheless, I would verify the condition of the 30Amp breaker as the consequences of its being bad and drawing too much current could be catastrophic to you and your family.

[RLS]

Originally Posted by Secguru

Nonetheless, I would verify the condition of the 30Amp breaker as the consequences of its being bad and drawing too much current could be catastrophic to you and your family.

I never thought about the inside 30 amp main breaker being bad. That would not be good How do you test a breaker other than putting a high load on it? It does switch off and feels normal on switching on or off.

Thanks,

[Jammer]

If the breaker is suspect, it's probably easier and cheaper to replace it than to test it. They cost less than $20.

Most electricians would not be suspicious of the breaker unless there were heat damage at more than one point in the shore power connection. Had an actual overload, rather than plug and socket problems, caused the damage, it would be present equally throughout the circuit, and burned or melted insulation would be present in the vicinity of the breaker as well as in the vicinity of the plug. If this is the case, all the damaged wiring should be replaced, in addition to the breaker.

Breakers that don't trip are rare (some industry sources estimate an 0.01% failure rate), aside from the notorious asymmetrical trip defect in older Federal-Pacific breakers.