It happened to me! Overloaded 30amp cord

[Scott'n'Wendy]

Then why didn't the breaker trip?

Because the breaker didn't see 30 amps or the breaker was faulty. The cord set did not have to see over 30 amps for a bad connection to melt down the plugs.

 

[Scott'n'Wendy]

If he was plugged into the 50 amp breaker with a 50 amp to 30 amp dog bone, then that probably would not trip the breaker. A 30 amp breaker should have tripped.

You can't know that with the info provided.

 

[coglesby]

The current did not increase, it decreased. The power dissipated at the plug was high because the resistance was high.

 

[MtnGuy]

You can't know that with the info provided.

I said “if”.

 

[jkwilson]

Time to let it go John...lol

I will never let that one go! Nor the one where I misplaced a decimal point and lost 25 points on a Dynamics exam. I was super prepared. Exam question was a slightly modified version of a homework problem. A spinning disk with a rectangular bar pinned out near one edge. My work was perfect until the last step when I substituted the mass from the homework problem (10g) for the 100g on the exam. My answer was 10.8N. The correct answer was 108N. Got a 78 (a D) when I would have gotten 104 out of 100 with the decimal in the right place. Dr. Wong was a jerk.

About the same time, in an antenna theory class, I somehow decided during an exam that 3pi/2 was 290 degrees. Plotted an elaborate antenna pattern based on that. Left the exam and was walking to my car and realized what I’d done. Went back to the room where the exam was going on and explained what I had done to the professor. I was just hoping if he understood my mistake he’d be generous with partial credit. He pulled my exam out of the stack, looked at it briefly and said “Fix it.” Gave full credit. Dr. Ko was great!

 

[jkwilson]

What was his "correct" answer?

He wanted time in there as well?

He wanted current squared. That’s just a math function. Heat is a function of current and resistance. Period!

 

[coglesby]

My dynamics teacher was horrible. I was happy to pass with a C just to get it behind me.

Weird how we remember this stuff like it was yesterday.

I still have nightmares. I have a reoccurring one where I realize I wasn’t attending a class on my schedule all semester and tried to study up for the final to try to squeeze out a passing grade. On finals day I couldn’t find the classroom to take the final. 40+ years ago and college still haunts me.

 

[dryfly]

. Got a 78 (a D) when I would have gotten 104 out of 100 with the decimal in the right place. Dr. Wong was a jerk.

I think Dr. Wong must have taught my Statistics 101 class also. You just can't forget those types.

Back to serious, I doubt any of us would make the same mistakes as in the OP as far as the electrical supply to our trailer, but my big concern is the duplex outlets used in modern RV's. The way they are constructed for connections seem really risky. I use a small 1500w heater and I cringe every time I turn it on. If it wasn't so much work and so little space to work with I'd swap them all out to residential outlets.

 

[CedarCreekWoody]

If he was plugged into the 50 amp breaker with a 50 amp to 30 amp dog bone, then that probably would not trip the breaker. A 30 amp breaker should have tripped.

I asked this question in post 10 but the OP has not responded to it.

 

[coglesby]

If one doesn’t understand electricity, they should never use dogbones on both ends.

 

[Hoopy Frood]

If one doesn’t understand electricity, they should never use dogbones on both ends.

So if you understand electricity, it's okay to use dogbones at both ends? Why would understanding help with the potential issues?

 

[coglesby]

So if you understand electricity, it's okay to use dogbones at both ends? Why would understanding help with the potential issues?

You can have a 30 to 50 dogbone at one end of a 50A extension cord and 50 to 30 on the other end so you have 30A breaker on both ends of a 50A cord. Other way around is bad news. If you understand electricity you should know that. Dogbone on one end is ok because opposite end should have appropriate breaker

 

[Scott'n'Wendy]

So if you understand electricity, it's okay to use dogbones at both ends? Why would understanding help with the potential issues?

Ya, what coglesby said. There are dogbone adapters available on amazon and similar sites that should not be available..... which leaves a #10 cord 'protected' by a 50 amp breaker.

 

[CedarCreekWoody]

Ya, what coglesby said. There are dogbone adapters available on amazon and similar sites that should not be available..... which leaves a #10 cord 'protected' by a 50 amp breaker.

Those are widely available and have a place when used properly. We don't even know if the OP used a dogbone - he's never said.

 

[coglesby]

Those are widely available and have a place when used properly. We don't even know if the OP used a dogbone - he's never said.

With a 30A surge protector and a 50A coach I assumed he used a dogbone but I think the problem was corroded receptacle and plug.

 

[Rabbit]

It all boils down to too many heaters (3) on a 30Amp supply. The weakest CONNECTION was the plug between the cord and EMS, which over heated and burned. Likely loose, corroded or dirty. This type overload can escape the circuit breakers. A 50Amp wired RV can severely overload a 30Amp cord and supply, and never trip a breaker in the RV.

 

[Scott'n'Wendy]

Those are widely available and have a place when used properly. We don't even know if the OP used a dogbone - he's never said.

There are non-code adapters out there that allow you to plug into a 50a service breaker and attach a 30a extension cord to it. It is not possible for such a device to be used properly. It is dangerous and there are lots of people who have them believe they are doing things properly with it but don't realize they have conditions for severely overloading their cord.

 

[coglesby]

I’ve had this happen with no dogbone or extension cord because I let the plug prongs get corroded.

 

[jkwilson]

I’ve had this happen with no dogbone or extension cord because I let the plug prongs get corroded.

Easy to happen. Most electrical contacts are just plated with a thin layer of brass. The base metal will rust when the brass gets abraded. People grease them thinking it helps, but it just catches sand and turns into sandpaper.

I switched my power connection to a Smart Plug. Better quality contacts and cleaner. Doesn’t help with extensions, adapters or the pedestal receptacle. I try to wipe the plugs with a dry cloth if they’ve been damp to at least keep them free of debris.

 

[Retbass]

Yep. My bad! I was using 2 portable electric heaters (low setting) and electric "fireplace" to provide heat in cold South Carolina weather early January (2025). My "rig" is wired for 50amp (though I have only 1 roof-top A/C). You all know how heavy and cumbersome 50amp cables are. . . . I switched to 30amp, buying used cable & surge protection. Mistake! Thank the Lord I was present when this cable burned up-quickly turn off breaker with no subsequent damage. Lesson learned . . . 50amp more efficient and would have prevented possible tragedy.

Yep. My bad! I was using 2 portable electric heaters (low setting) and electric "fireplace" to provide heat in cold South Carolina weather early January (2025). My "rig" is wired for 50amp (though I have only 1 roof-top A/C). You all know how heavy and cumbersome 50amp cables are. . . . I switched to 30amp, buying used cable & surge protection. Mistake! Thank the Lord I was present when this cable burned up-quickly turn off breaker with no subsequent damage. Lesson learned . . . 50amp more efficient and would have prevented possible tragedy.

Cor

Were your plugs were left out in the weather and got wet and then corroded adding significant resistance in the plug area?

Corrosion or loose connections would damage the plugs like that. Never good to double up plugs like that. Dog bones and surge protectors together are not good. Every extra connection can cause problems. Surge protectors arent worth the money just problems.
I have been camping in 50a camper without surge protector since 2005 and have never known anyone that had a surge and hurt anything only problems caused by surge protectors.