Can A/C cause power cord failure?

When my power cord overheated and burned a hole in the plug today, the only heavy drain was my A/C.  Does this mean that the A/C needs to be checked out, replaced, or simply replace the plug?  A/C has been in frequent use these past few weeks (in Florida) but performed flawlessly.  What really puzzles me is why it shorted out without tripping the circuit breaker in the RV or in the Park.  Thanks.
Hockeybuff
2008 Winnebago Outlook Class C

Most likely, the plug had a bad connection internally and the higher current demand from the A/C overheated it.  The A/C probably was NOT drawing excessive current which is why no circuit breaker popped.  You just had a bad plug.  Replace it and you should be okay.

More likely the plug has one or more broken wires in it, resulting in some resistance and resultant overheating.  Over load from the A/C or any other thing in the RV would trip the circuit breaker, either in the RV or on the pedestal.  Replace the plug.

Ned said:

More likely the plug has one or more broken wires in it, resulting in some resistance and resultant overheating.  Over load from the A/C or any other thing in the RV would trip the circuit breaker, either in the RV or on the pedestal.  Replace the plug.

Click to expand...

Isn't that basically saying the same thing as "the plug had a bad connection internally"?  It could be broken wires or a bad crimp or loose clamp depending on how it is constructed.  Granted, it is probably broken wires, but doesn't have to be.

If you are pulling more amps than the plug can handle, you will melt the plug.  If this is a 30 amp power cord, and you were plugged into a 30 amp circuit, the only explanation is a short in the plug.  If you were using a lighter cord connected to the main power cord and that plug melted, excessive heat from the amps. 

If you were pulling more than 30 amps you should have heard "The Click of Darkness" (Tripped the breaker) so no.

Plugs get old..Two things happen (So do outlets)

1: IF wires break or manage to get loose inside the plug this means your 30 amp plug is now a 20 amp, or even a 10 amp plug (Depending on how many strands of wire break/come loose).. Exactly as others have suggested.

And the blades tranish due to the effect of air and time,or due to poor connections and due to failure of the owner to turn the breaker off before connecting/disconnecting.

This too brings up the resistance, and lowers the capacity of the plug..


The one thing that can NOT cause it is a short inside the plug... That would trip the breaker.

Interesting that your original focus was on the appliance. Would suggest after you fix the problem you check out a copy of Electricity Demystified from your local library and then get a copy of one of the rv maintenance guides. You should be thinking 1) from a systems point of view 2) from the source downstream, rather then the load upstream, and 3) as a closed circuit.

When you have a loose connection it reduces the voltage. The appliance is trying to pull the watts it needs so more amps are demanded to make up for the reduced voltage. See watts law. Watts = Amps times Volts.

That is why the wiring and the plug is heating up...the circuit was pulling more amps than it should have. This can happen before the breaker trips or if the breaker is defective....amount of current varies. A good breaker should help prevent you personally from receiving a deadly shock. The circuit breaker system is designed so that when you try to pull too much current through a particular circuit, the breaker shuts off and stops the flow of electricity through it before a potentially hazardous situation develops. In the world of circuit breakers, this is what?s meant by ?tripping?. By doing this, the circuit breaker protects the circuit and its wiring from overheating and causing damage or starting a fire.

Three of the reasons for electrical overheating that leads to electrical fires are excessive current, poor connections, and insulation breakdown. Excessive current is rare, because circuit breakers and fuses (if sized correctly) typically protect against this occurrence.
Poor connections can be very efficient at overheating, because they can generate a high wattage over a small area for a long period of time without tripping the breakers. (again...high wattage) If the watt density is high enough, the connection will glow. An oxide actually forms at the (loose) contact area, and the resistance of the oxide causes the I2R power dissipation. I = amps, R = resistance. A GFCI or AFCI may sense a poor connection after some electrical insulation becomes conductive and leakage current occurs (5 mA or 30 mA, respectively). If a breaker isn't tripping, yet still feels quite warm, you probably are close to having too many appliances on its circuit. Breakers trip because of overloads (too many appliances), or shorts ( bare wires touching each other).

Before you do any work yourself, on electrical circuits, equipment or appliances, always use a test meter to ensure the circuit is, in fact, de-energized.

This would be a good time to go look at your white wires in your electrical cabinets to see if any are turning from white to tan to brown (be sure it isn't dirt you are looking at). You may have more wiring problems now or on the way.

When I worked a switchboard in the service, I was always reminded to keep brass and copper connectors shiny. I use one of the wife's disposable emery boards occasionally to shine up the plugs on all cords.

Don't feel bad about your 2 year old cord failing.  Being an electrician by trade and having worked in several campgrounds over the years, I have seen more 30 amp plug and socket problems than not.  They just seem to fail that is both sides, the plug and the socket.  Once one side overheats both sides fail.  Then the next guy uses the socket and his plug fails and on and on similar to a cold virus transferring between students in a school classroom.  When the socket is replaced and a good plug is used the virus stops.  Keep an eye on your 30 amp plugs!

Good luck.

Very few applications subject high current plugs and sockets to the number of insertions and removals that a RV pedestal and your shore power plug go through.

Install an electric dryer or stove and the plug will be inserted once, and only removed if the appliance is serviced or replaced.

Contrast that with the daily cycling RV park sockets undergo.  Once the socket contacts wear down they lose tension and no longer make good contact with your shore power plug.

You can't do anything about the sockets you're plugging into, but you can inspect your shore power plug and replace it when it starts showing signs of overheating or wear.

If you have been camping near an ocean, the contacts can easily get corroded and the poorer contact can cause  a lot of heat.  Also, the contacts on the pedestal can get corroded as well.  We've had to call the office at a couple of campgrounds to have it corrected.

If you have a 30 amp service, the park receptacles are famous for being worn out and loose and causing over heating and melting of the plugs.  Very common problem.  Glad I have 50 amp service.

I have heard of people buying a 50 amp to 30 amp dogbone just so they can plug into the 50 amp receptacle on the pedestal. This has two advantages, one-it starts your service in a less used and therefore tighter socket, and two-it won't be tripping a possibly weak 30 amp breaker on the pedestal and therefore eliminates a trip outside to reset.

The hot sun shining directly on an already over heated plug also contributes to failure

My 30 amp brand new cord was melting and getting hot. With a.c. running all day. Brought a 50 amp dog bone connected. It no longer get hot and melts. Worked perfect. Went through two cords before. Now can still use a half burnt one no problem. I will get another cord. But I will definitely use the dog bone in thefuture

Hurricane2005 said:

My 30 amp brand new cord was melting and getting hot. With a.c. running all day. Brought a 50 amp dog bone connected. It no longer get hot and melts. Worked perfect. Went through two cords before. Now can still use a half burnt one no problem. I will get another cord. But I will definitely use the dog bone in thefuture

Click to expand...

I think what you're saying is that you now plug into the 50 Amp outlet instead of the 30 Amp outlet. That makes sense because the 30 Amp probably got used a lot more over the years and is worn out.
Oh, welcome to the forum.

yes.

I've owned and lived in this 30 amp motorhome for 6 years in the same rv space.

I typically draw about 27+ amps all day everyday during the summer.  I have replaced 3 melted cord plugs so far.  Every time I shorten the cord by 4 inches to get rid of the heat fused wires at the end.

It has never tripped the 30 amp pedestal breaker before...the power just shuts off,  and it always melts the yellow plug and the neutral blade always stays in the receptacle when I yank the burnt plug out of the pedestal ,    I go buy a new Camco yellow 30 amp plug, and shorten the cord and it lasts a couple years.

The factory plugs can melt,  and the yellow replacement plugs melt even easier because the wires are attached with screws inside the plug.

Question was it the plug end that was "Burning up"?

THe dogbone has a good CLEAN 30 amp outlet. But the park's is well used.  And there in lies the issue.

yes it melts the end of the 30 amp rv cord plug.......and it even did it once when I had it plugged in at my shop one summer, on a brand new service and receptacle I installed for the RV spot.

As an old  IBEW journeyman electrician and a former C45 electrical contractor I do look inside the pedestal receptacle with a flashlight clean out any debre and have taken my knife and scraped the contact blades clean and sprayed contact cleaner on them.  but it keeps happening.

I don't use a dog bone adapter or a plug in surge protector,  the M/H cord is plugged directly into the pedestal,
IMO..the more plugs you have, the more problems you have.  My motorhome's Intellitec energy management system has nice built in protections,  so I let it do it's job.

If an electrical part is rated at 30 amps max....and it runs at 30 amps it's whole life...it will live a short life.