Dogbone Melted

[allen8106]

Have any of you guys seen anything like this. My 2010 Jayco has 50 amp service and is usually hooked up to power to keep the batteries charged with a 50-30 amp and a 30-20 amp dog bone adapters. In this particular instance there has been no power draw on the rig except the converter and maybe a light or two on occasion if we enter the camper at night or need to run a slide out.

I suspect maybe moisture got inside the connection and caused a short which over heated the connection. The breaker inside my work shop that powers this circuit was tripped also.It's been raining a lot lately and this connection was exposed to the rain.

[stevenicol]

I did this very thing last season. I needed a 20amp connection; however, there were only 50amp connections available. So, I plugged a 50 to 20 dog-bone to plug in the trailer; the dog bone melted. Lesson learned.

[fourthclassC]

Agree with all replies here. Really good info. Just one item to add. The prongs of the plug head that are molded in can be bad, inside the molded area. I suggest checking to see if the prongs are loose on any plug or adapter before using.

[Sam_Spade]

beemerphile1 wrote:
Not likely water had anything to do with it.

And how, exactly, did you arrive at that conclusion ?

A WET connection is a BAD connection.

IF.....the connection pictured had been outside in a significant rain event, it is highly likely that water DID have something to do with the severity of the result.

[beemerphile1]

Chris Bryant wrote:
That's not really due to a short, it's due to a high resistance connection, either due to corrosion, or bad molding- I've seen them where the contact was covered by plastic.
Once the thing melted, then it shorted, but the short didn't cause the damage.

Like Chris said, the short that tripped the breaker came after the socket/plug overheated due to a poor connection. Not likely water had anything to do with it.

[allen8106]

John&Joey wrote:
Yes it happened to me, but not nearly that bad.

Friends in a 5'ver came to spend a week with us. Best I could offer was a 15 connection. They never ran the AC, but it did fry the 15/30 dogbone. It was plugged into a GFI also. It was a black dogbone, not the yellow Camco.

Surprisingly mine had no power draw other than the converter.

[John_Joey]

Yes it happened to me, but not nearly that bad.

Friends in a 5'ver came to spend a week with us. Best I could offer was a 15 connection. They never ran the AC, but it did fry the 15/30 dogbone. It was plugged into a GFI also. It was a black dogbone, not the yellow Camco.

[wa8yxm]

See it often.. Question.. Do you inspect and clean the blades on the plug before you plug in? Are they bright and shiny or heavily tarnished and almnost black


Reason for asking

The cause is not moisture, though that may be a precipitating event the cause is tarnish on the blades (We call 'em pins in electronics) Unlike Gold oxcide copper and brass when they tarnish the resistance goes up, as the tarnish increases the resistance of the connections goes up Resistance + Current = Heat and well you have seen the evidence of that.

Note also.... A bad connection WITHIN the plug body.... Same thing, more resistance = more heat = what you saw.,

[myredracer]

I have seen a few photos of worse and is not a rare occurrence.

Have you perchance been plugging in with the power still live? If so, the converter has an inrush current (capacitor charging current) that causes pitting and attracts dirt and then you end up with a high resistance connection that can overheat and melt. Sometimes the retention force inside a cord connector, pigtail adapter, pedestal or home receptacle can be weak which can contribute to the situation of dirty plug blades. It's good practice to keep an eye on the shore power cord's plug blades (and adapters) and clean them with emery cloth or sandpaper as needed. When you plug in live, you can hear a zap and in the dark can see a flash.

The problem with cord connectors and receptacles is that you can't see inside them to tell if they are pitted and dirty. Have come across some pedestals that have loose and crispy-looking 30 amp receptacles that just shouldn't be used, but sometimes you may not have a choice. I use a 30 to 30 amp pigtail adapter in those cases so if it overheats, I'd only lose the adapter. Reducing loads to a min. will help too. Be wary of a receptacle that is obviously loose. I had to use a stick once at a pedestal to hold the plug in place (no other sites with better pedestals).

In the beginning, I had the connectors on two cheapo variety 15 amp extension cords go up in smoke because I was plugging our TT in with the power live. Once I started turning the power off, it never happened again. I ended up installing a dedicated 30 amp recept. for our TT in the carport along with a disconnect switch next to it.

[time2roll]

This would be a good time to install an outdoor NEMA 14-50 and stop using adapters.

No I have never seen it that bad in person. Only posted here by others.

[phillyg]

I'd suspect it's age related, bad manufacturing, or inadvertant stressing of one of the lines or fittings, or a combination thereof. Regardless, the circuit breaker did its job and nothing burned down.

[2oldman]

allen8106 wrote:

2oldman wrote:
Seems to me if it was a short the breaker would have tripped.

The breaker in my shop did trip.

Evidently not in time.

[landyacht318]

I am not familiar with these types of connectors, and do not care to become so, as they appear to be horribly engineered for passing the currents asked of them.

Lots of pics in following link showing tiny contact areas.



http://www.pbase.com/mainecruising/installing_a_smart_plug

[pianotuna]

Hi allen8106,

You may have to make your own. I have moved to using progressive dynamics for female outlets. I am in a 30 amp RV so I use #10 wire that is rated for cold weather and UV protected.

allen8106 wrote:

pianotuna wrote:
Is it a Cameco female connector? I find those unreliable and subject to burn on low loads.

They are both Camco, the 30-15 is a few months old, the 50-30 is 10 years old.

Is there another brand besides Camco available?

[Chris_Bryant]

That's not really due to a short, it's due to a high resistance connection, either due to corrosion, or bad molding- I've seen them where the contact was covered by plastic.
Once the thing melted, then it shorted, but the short didn't cause the damage.