Yes, almost everyone I know has had to replace power cords within the last year. The new stuff they are producing is just crap!

 

No problems with 50A (1) or 30A (2) cords, all less than 3 years old.

 

Make sure you keep the prongs very clean. Resistance = heat.

 

Cleaning the contacts on the cord (as it is sealed) would seem close to impossbile. Also, all of the failures I have noted are in FRESH water... not salt - an important distinction. Also, in none of the instances has there been shown ANY corrosionon the receptacle. That in turn leads me to believe it is on the cord - if it is the cord that is the issue.

- CD

 

It seems unlikely to me that they are producing their cords to the rated specs. The cords should be able to handle 30 amps continuous withou overheating or burning up. THat does not seem to be the case in any of these instances.

I am not sure the exact series of events that causes the failure. It is possible that corrosion is building up on the terminals inside the plug. That in turn causes more heat. THe heat in turn causes more corrosion until it is a vicious cycle.

That is my rough guess at this time. However, it is getting hot enough that the enire receptables is melting down and failing. THe failures do not, in any instance, stop at the plug. They over heat to the point of causing the plastic structure of the receptacle to literrally burn up such that when you pull out the plug you will quite literally pull out the entire prongs of the receptable (often a hot wire... you should note).

Has this been others experiences too?

- CD

PS In 15 years of boating, I have never had this problem on previous cords - including when we were liveaboards in FL on CRUDDY power.

 

Here is a pic of one of the plugs.

 

I had the same problem and returned 2 of them to West Marine. Their catalog showed a 5 yr. warranty. They replaced them after calling the home office to find out what the 5 yr. warranty covered.
You will have to also replace the receptacle insert so that the prongs are clean.

 

Yes, we replaced the receptacle too. Thanks. I did not return for money back. THat is a mistake I will not make again (as they are quite expensive).

Thanks for the input.

- CD

 

Besides keeping the contacts clean, make sure you take the time to screw down the black retainer ring all of the way. That will help assure the connection is good. You can test it by putting a good load on it for a while and then remove the plug - it shouldn't be hot. If it is, and the cord is clean, ask the marina to change the outlet.

 

Thirty-amp connectors are a perennial problem in marinas. I've seen many failures and meltdowns over the past couple of decades. Many of these could be traced to "user failure", i.e., overtaxing the connectors by overloading them, not cleaning them, not keeping them dry, etc., etc.

The sad truth, however, is that we're now seeing FAR TOO MANY failures of 30A Marinco connectors to believe that its always "user failure".

First, the design stinks: these things cannot handle anywhere near 30A continuous power, without heating and burning.

Yes, do everything possible to keep contacts clean and dry, and try to limit power draw to not more than 25A or so. That will help.

But, bottom line, IMHO these connectors are real crap. Be very wary of them....i.e., ALL 30A connectors....but, especially, those recently coming out of Marinco. These seem to be substandard in construction.

Is this really the best we can do?

Bill

 

Thirty-amp connectors are a perennial problem in marinas. I've seen many failures and meltdowns over the past couple of decades. Many of these could be traced to "user failure", i.e., overtaxing the connectors by overloading them, not cleaning them, not keeping them dry, etc., etc.

The sad truth, however, is that we're now seeing FAR TOO MANY failures of 30A Marinco connectors to believe that its always "user failure".

First, the design stinks: these things cannot handle anywhere near 30A continuous power, without heating and burning.

Yes, do everything possible to keep contacts clean and dry, and try to limit power draw to not more than 25A or so. That will help.

But, bottom line, IMHO these connectors are real crap. Be very wary of them....i.e., ALL 30A connectors....but, especially, those recently coming out of Marinco. These seem to be substandard in construction.

Is this really the best we can do?

Bill

Hi Bill... how are you?

Thanks for the input. Yes, I think I agree with you. But you would think (using the 20% rule), they would over size their cords/connectors for continuous operation at 30 instead of 80% of 30A. I wonder if that is not the case?

- CD

 

Are you getting a full 120 volts? If the marina is providing less, that could cause the problem too.

The cords may be crap - I have no way of knowing for sure. I'm just trying to mention thing that you have some control over.

 

I had already thought of that too.

Yes, on a normal day, we are getting good power. The question is whether it stays good?? That, without putting it on a meter/printout, I cannot know. But the problems associated here are not solely out of my marina which leads me to believe that, unless highly coincidental, it is not the major problem.

- CD

 

CD, I have had the same problem. Has it been the same slot on the receptacle end in both your failures? I have a feeling that all the failures are on the same slot and that this is a result of not completely turning the plug before tightening the holding ring and because of the configuration of the blades full contact is not made. If this is the case it is neither corrosion nor poor workmsship that are the cause of the failure.

 

I am not sure about that. I would have to check.

- CD

 

I have seen it also

On most cases at our marina, the plastic ring that is supposed to hold the connectors tight is broken or was not used. The twist lock function of the plug itself will not hold the plug in.
Insurance companies are checking this when there is a claim.
That plastic ring breaks easily when dropped, and I don't think it can be replaced, so you have to buy a new shore power cable.
Hummmmmm! could this be on purpose?

Fair Winds

Cap'n Dave

 

I think you will find that it is always the same slot. It would therefore appear to be a design flaw in their female cap. I do not recall seeing this problem anywhere else, so it may be more of a problem with Marinco. I do know that by insuring to turn the female cap to the lock position and tightening the locking screw ring it doesn't heat up. Note that once heating starts the contacts produce their own resistance furthering the heat build up so periodic cleaning will help. My feeling is that there should be a positve feeling of locking the plug in postion and I certainly don't feel that. Next time I'm in Home Depot I'm going to check other manufacturers male and female cap connections.

 

I am dealing with different cordsets every day...maybe a few hundred each year and would say that the majority of cordsets have similar burning to what is shown. I would guess that 90% of the cordsets are marinco since it is what is generally available and sold at the major boating stores. I rarely see any burning on 50amp sets and I have always attributed it to the much more robust contact and locking mechanism. I think the 30a plug/receptacle design is flawed regardless of the manufacturer...but how do you change a "standard"??

 

It is pretty tough to change a standard without overwhelming proof that a newer standard would have significant benefits...

 

If you routinely connect/disconnect with the power on, internal arching inevitably can occur causing the burn marks in your picture. As you can imagine, the instantaneous connection/disconnect, particularly if the conenctor pins are dirty, can arch. I don't know if you do this but I've seen many people do it and, correctly or not, I attributed their failed connectors to that process.
It's always a good habit to first shut down the breaker before disconnecting.

 

K1,

When you say "shut down the breaker", are you referring to the shore power breaker in the boat, or out on the dock? I always shut down the breaker in the boat, but have never shut down the breaker at the dock. In all honestly, it never occurred to me that I should do that...

 

Marinco power cables

I too had one go like that and I wondered if I had been neggligent in making sure that the twist-lock was all the way over and then tightened the retainer ring.
It is easy to become non chalant about some of these things
A thought
George

 

Shutting down the dockside breaker is something I always do before plugging in a transient boat. Then I ask the captain if it is ok to turn it on.
Surprising how many look at me like they've never considered that question before!

 

K1
Does it really matter if the breaker on shore is off... if the breaker at the boat is off and there is no flow of power?

I do think this is a combination of things.
Poor connection due to not twisting the connector on all the way.
Wiggling the cable and causing arcing.
Plugging and unplugging while power is flowing.
Salt & other stuff causing corrosion and poor connection.

This came up on another list and Hubbell was mentioned as using a different method of connecting the lugs to the wires. Sorry I don't recall the differences.

Rings can be forced on to the plugs, I've done it. I don't recall ever seeing a dockside recepticle with threads for screwing the ring to.

 

You are right that if the breaker on the boat is off there will be no current flow in the cord. However, I would turn off the dock side breaker before unplugging, just because working near salt water around a live 30 amp cord seem like a bad idea to me.

If you don't bother with turning off the main breaker on the boat either, you could get some arcing when you connect or disconnect.

 

You are right that if the breaker on the boat is off there will be no current flow in the cord. .

WRONG!
We're not talking about current flowing on the cable. That has absolutely NOTHING to do with it.

The thread is about the cable ends arching thereby destroying the pins and the cable which occurs every time you connect/disconnect to a live plug..

If you don't believe me, do a simple experiment at home by plugging in a lamp (while shut off) to a socket slowly - you'll see the arch at the junction.

Believe it or not - your choice and I'm sure Marinco thanks you for not believing.

 

Farcry,
I got you. It's true that when you throw you boats AC main breaker you are creating an arc inside your breaker, not the pedestal breaker. I don't ever throw the AC main with other AC breakers in the on postition, so the load is minimal. I my only load at that point is the not loaded AC panel.

******
Opening just the boats main AC breaker only isolates the AC panel, and everything that it serves. The wiring between the boats AC main breaker and the shorepower cord recepticle is still hot if the pedestal breaker is closed (or "On").

See this diagram I just found online:

 

Here is a "grown up" version of what happens when you just disconnect power without opening the breakers on both sides first. A 120v arc is much smaller, here is 500Kv.

 

Snapper ya got it all wrong

If there is a load on one end of a power cable then you will get acring because current is flowing. If nothing is present to put a load be it a lightbulb, short, or whatever nothing will ever happen.
In your little movie current. is flowing, therfore the arc. It has to have somewhere to go to arc.

Fair Winds
Cap'n Dave

 

If the pedestal breaker is closed, and the cord is plugged in, there is current present. you are connecting a live line to a dead bus. The first video shows what happens when you disconnect with both sides live. Here is a video of what happens when you close a live line onto a dead bus (No load at all, just the conductor section). This a large scale version of what happens when you energize a dead bus with absolutly no load on it.

this is the reason the breakers are closed last, so the arc is contained within the breaker.

Edit:

If nothing is present to put a load be it a lightbulb, short, or whatever nothing will ever happen.

live line dead bus means that the dead bus will be the load, you are energizing with the cord (live line provided the pedestal breaker is closed) wiring between your recepticle and your AC main breaker (the dead bus)

 

I'll stick with my statement. If you have no load on the shore cord, such as the main breaker on the boat being off, it wont arc. The video is not an accurate representation of what's happening on the dock because there's voltage threshold effect that we don't meet in the dock example.

 

Ok, I would like to clarify a few points:

First, this is in fresh water. Obviously it is happening in salt water too - but the examples I am using are all fresh.

Second, there was NO corrosion on the terminals of the receptacle. I do not know about inside the cords as that is not visible on a sealed cord. Of even more interest, on Dad's cord that burnt up, it was where a female and male Marinco cord hooked together - and not the boat terminal.

Third, I have been boating a long time. I have never seen this happening until recently.

Fourth, the point has been made about improper locking/unlocking. It has also been suggested that the rings were not fully screwed in. In ALL cases, I have personally screwed in the rings. Not an issue for me. On dad's boat, I guarantee you that it was screwed in as it was male-female cord connections. I do not know on the other 400 - but as he is a long term cruiser, I would have to assume he also screwed his in... but again, I am not sure about that. Also, since I always plug in the cords, I can guarantee you that they were always completely locked.

Fifth, I won't say that I have never forgotten to flip off our power... I am sure it has happened. However, it would be by far the exception than the rule. That being the case, it seems unlikely to me that flipping on/off the power is the culprit.

Let us not forget that these cords are made to be removed and replugged in. That is their design. They are also designed, supposedly, for the marine environment. If it says 30A cord on it, I expect that to mean that I can pull a SOLID 30a without overheating. In theory, they should not ever be subject to more than 30a for very long. In order for them to exceed 30a, you would need a failure of: 1) the Main breaker at the dock (30a), 2) the main breaker a the boat (30a), the main breaker at the panel (30a). It seems HIGLY unlikely that we would have that many failures on that many different boats with that many circuits. It should also be noted that my second cord that failed was plugged into a completely different receptacle with different breakers at the dock and boat.

At this point, I am beginning to feel the cord is suspect. I am concerned they have changed something in their manufacturing in the last few years. That is why I am probing many of you on this. Also, I want to eliminate the likelihood that it is dock, marina, or boat specific.

- CD

 

Sorry to drift off topic. I've had no problems with my cord and I know I run very near 30 amps sometimes since I've tripped my 30 amp breaker a twice. My cord is at least 10 years old, which may add to your case that the new cords are not as well built as the old ones. Are the cords you have seen burn up all been new(ish)?