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Old 02-11-2014, 06:16 PM   #1
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Melt Down Anybody??

Can anybody identify this mess??


Yes. . . It's a Smart Plug and it came off the boat near me!!

We have had two boat in our area, while at their respective docks melt down their Smart Plug shore power plugs. One was owner installed and the other by a licensed electrician. The company is blaming cold weather and on board heaters??

ps: I was looking at their website and I see they have an ETL approval, but not UL for the SmartPlug system??

Anybody have similar problems??
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Old 02-11-2014, 07:27 PM   #2
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Originally Posted by Edelweiss View Post
Can anybody identify this mess??
Yes. . . It's a Smart Plug and it came off the boat ??
Maybe the Marina has a problem. If there is an overload on the boat the 30 amp breaker on the dock should kick out. Or how about low voltage?
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Old 02-11-2014, 07:43 PM   #3
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I was trying to figure out why my microwave wouldn't heat a cup of coffee and is I stuck my meter in the sockets - 88.5 volts! I started unplugging things and got the voltage back to 110 but it's straight Ohms Law, I figured I was drawing 40 amps off a 30 amp system and the marina's breaker didn't pop. Still haven't talked to them about it.
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Old 02-11-2014, 07:56 PM   #4
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Salt plus high humidity creates corrosion on shore cord connections. Corrosion leads to high resistance. High resistance plus high amperage (winter heaters) leads to heat at the connections.

This is one of the leading causes of boat fires. You are lucky it only burned up the connector.

A 50-odd foot sportfish caught fire at the dock here a few weeks ago. Shore cord connector. Fortunately, fire was put out before it was engulfed.

Are leads tinned? Looks like they used shore cord cable for interior cable, I don't think that is tinned. Non-tinned more prone to corrosion.
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Old 02-11-2014, 08:14 PM   #5
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Salt plus high humidity creates corrosion on shore cord connections. Corrosion leads to high resistance. High resistance plus high amperage (winter heaters) leads to heat at the connections. This is one of the leading causes of boat fires. You are lucky it only burned up the connector. A 50-odd foot sportfish caught fire at the dock here a few weeks ago. Shore cord connector. Fortunately, fire was put out before it was engulfed. Are leads tinned? Looks like they used shore cord cable for interior cable, I don't think that is tinned. Non-tinned more prone to corrosion.
We just ran some shore cord cable (bought it at pacer on a spool) which was marine grade, and it was all copper not tinned.
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Old 02-11-2014, 08:20 PM   #6
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30 amp connectors with poor locking rings. Water intrusion resulted in high resistance connection and eventual melt down, Pretty scary stuff when you discover it. This was on a friends sailboat.
Back when I was a bubble head EM I saw a 1200 amp shore power cable melt down on the hull, really scary!
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Old 02-11-2014, 08:22 PM   #7
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Originally Posted by Edelweiss View Post
Can anybody identify this mess??


Yes. . . It's a Smart Plug and it came off the boat near me!!

We have had two boat in our area, while at their respective docks melt down their Smart Plug shore power plugs. One was owner installed and the other by a licensed electrician. The company is blaming cold weather and on board heaters??

ps: I was looking at their website and I see they have an ETL approval, but not UL for the SmartPlug system??

Anybody have similar problems??
Their website goes on and on about how their design prevents overheating. It also indicates that they have a built in trip thermostat that cuts off the power when the unit overheats. So, why didn't the 'trip thermostat' cut off the power when the unit overheated? Well, the simplest explanation is because it is the trip thermostat that melted down. Hardly unusual if a PC board of some type is involved since these are frequently not fused with the result that even a .1 amp short will cause the things to catch on fire. My son's house almost burnt down when his Bosch dishwasher PCB, like many others, caught on fire without tripping the breaker.

If the company seriously is offering on board heaters or rain as a reason for these melt downs, I would steer well away from their product, since that would appear to be transparent B.S.
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Old 02-11-2014, 08:48 PM   #8
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Maybe the Marina has a problem. If there is an overload on the boat the 30 amp breaker on the dock should kick out. Or how about low voltage?
Note the attached piece of dock cordage does not show excess heating or melting beyond the plug housing (water proof housing has been removed). Whatever the cause it appears to be internal to the plug, probably caused by arcing. The boat is a 2 year old tug. I'll get a look at the boat side of the plug this weekend. Don't know if he was using electric heaters or not. I know he has a diesel furnace.

The failures occurred at two different marinas. Our docks and
the Ports electrical are all new. We'll test his breaker just for kicks though.
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Old 02-11-2014, 09:45 PM   #9
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Sure glad I didn't jump on the Smart plug bandwagon ...guess "smart" is in the eye of the beholder.

I have had several plug meltdowns but in the end...vigilance and maintenance are the best deterrents to electrical issues.
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Old 02-11-2014, 10:24 PM   #10
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Without even investigating further, the problem is overloading.

The boats are flat overloading the circuits.

What people do not understand is that circuit breakers are not designed to react well to long term overloading conditions. They react very well to sudden applications of high current but not so welll to marginal overloading.

OK, circuit breakers work on a principal of inverse time overcurrent. What that means is that the time it takes a breaker to trip is inversely proportional to the current detected. More current, faster the breaker trips. Less current, the slower it trips.


So, its plausable to pull more than 30 amps through a breaker and not have it trip at all, or not for a very long time. Pull larger current and the breaker will trip faster.
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Old 02-11-2014, 10:33 PM   #11
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Without even investigating further, the problem is overloading.

The boats are flat overloading the circuits.

What people do not understand is that circuit breakers are not designed to react well to long term overloading conditions. They react very well to sudden applications of high current but not so welll to marginal overloading.

OK, circuit breakers work on a principal of inverse time overcurrent. What that means is that the time it takes a breaker to trip is inversely proportional to the current detected. More current, faster the breaker trips. Less current, the slower it trips.


So, its plausable to pull more than 30 amps through a breaker and not have it trip at all, or not for a very long time. Pull larger current and the breaker will trip faster.
It has been documented I think by the NTSB that regular marine type CBs are pretty suspect as well as many aviation ones...at least into the early 2000 era for allowing slow overheating of wires to the pint of starting fires. Household CBs actually fared quite well in doing their jobs over a variety of tasks.

A few years back I couldn't get a brand new 20A marine CB to trip by sticking a screwdriver into a cigarette lighter plug to the point where the screwdriver welded itself into the socket. Not sure what was going on there...second breaker tried would trip.
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Old 02-11-2014, 11:02 PM   #12
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Without even investigating further, the problem is overloading.

The boats are flat overloading the circuits.

What people do not understand is that circuit breakers are not designed to react well to long term overloading conditions. They react very well to sudden applications of high current but not so welll to marginal overloading.

OK, circuit breakers work on a principal of inverse time overcurrent. What that means is that the time it takes a breaker to trip is inversely proportional to the current detected. More current, faster the breaker trips. Less current, the slower it trips.


So, its plausable to pull more than 30 amps through a breaker and not have it trip at all, or not for a very long time. Pull larger current and the breaker will trip faster.
Possible, but not likely. The CBs on a marine pedestal are generally standard issue and yes, they will trip faster the greater the amperage they are subjected to, but we are talking a difference in milliseconds. Once you get to the point of melting wires ABSENT A PCB that can melt and cause fires at fractional amperage you have more than sufficient current to trip the breaker. If this wasn't the case, housefires would be rather more common.

If the breaker in this situation tripped, it didn't trip until after the melt down, which means that something had to be able to melt down at less than the breaker amperage. That something is highly likely to be whatever circuitry is used by SmartPlug in making their "trip thermostat", not overloading which would have tripped the breaker unless it is defective - possible but extremely unlikely.

Even if a 30 amp breaker were defective and allowed, say 50 amps to pass through it, the fact that this plug would have melted at that amperage would mean it was grossly under designed and should be avoided on that basis. I doubt that is the issue here, and expect, as noted, that the circuitry involved in their cute 'trip thermostat' that is designed to avoid overheating will likely prove to be the culprit.
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Old 02-11-2014, 11:46 PM   #13
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Looks like a loose neutral wire connection to me.
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Old 02-11-2014, 11:47 PM   #14
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A corroded connection can burn up at an amperage well below the breaker trip setpoint. That's where a lot of the danger is.
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Old 02-11-2014, 11:52 PM   #15
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No matter how smart the plug is, an accidental dip into seawater will hasten corrosion.
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Old 02-12-2014, 12:35 AM   #16
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So, some folks do not really beleive me when I say that a breaker can be significantly overloaded and still not trip.

Please see the link below to a square d breaker curve for a molded case circuit breaker, which is pretty typical of what we see in marina peds.

http://static.schneider-electric.us/...0600DB0105.pdf

Here's the data.

at 1.5X the rated current (45 amps), trip time is between 90 and 400 seconds.

At 2X the rated current (60 amps) trip time is between 30 and 100 seconds

At 3X the rated current (90 amps) trip time is between 10 and 35 seconds

You guys get the idea.

How many amps, over how much time will it take to burn up #10 wire, and the connectors?

Boats burn up every year because of overloaded circuits. Owners trust the circuit breakers instead of managing the loads properly themselves.

But Alas there is some protection that works better. What I showed you above was for a SQUARE D brand molded case circuit breaker. Again, this is an industry standard for shore power feeds.

You can upgrade the protection in YOUR boat. Its simple. Replace your stock breaker with one of the Blue Sea shore power breakers. Posted below is the link to the product data page.

http://www.bluesea.com/products/7220...ingle_Pole_30A

This is a "faster" breaker having a trip of...

30 amps trips in 2-500 seconds
60 amps trips in .5 to 20 seconds

This faster breaker is much better. You cannot change your shore power. You can change the breaker in your boat.

Remember, especially you liveaboards. Load managment is up to you. Its your life at risk. Do not push the envelope.
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Old 02-12-2014, 01:13 AM   #17
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If leaving a boat connected to shore power for a long period, would it be feasible to use dielectric grease to reduce the potential for corrosion on the plug?

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Old 02-12-2014, 02:02 AM   #18
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Just had a email chat with Terry at SmartPlug, he is aware of both failures and here is his reply:

"This failure is due to a poor installation. The electrician or boat owner did not follow the instructions. I have provided you with the photos below of the other boat in the Anacortes area that had a connector failure. You can have the best product but if it is installed incorrectly they will fail.

Notice how there are no compression/bit marks on the yellow exterior sheathing of the cord. These photos document that the installer did not read the instructions to properly install our connector. The cord restraint jaws are designed to grip the yellow sheathing of the cord to eliminate pulling and strain on the wires that are installed in the connector. After prolonged use the pulling strain on the wires caused them to come loose which results in the failure as pictured in these photos. Please see the illustration below that is included with the installation instructions."

All I know is when I installed mine it was tough doing up the screws as to the pressure being put on the yellow jacket. No affiliation with Smartplug, just a happy customer.
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Old 02-12-2014, 02:15 AM   #19
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Maybe this is one of the advantages of our system, (in fact most of the rest of the world) where we have 220-240 volt supply. ie Higher voltage = lower amperage or current. My impression is we have much less of this kind of trouble over here in Oz, although corrosion can still be an issue. I pull my plug both ends and clean it regularly, and apply a corrosion inhibitor.
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Old 02-12-2014, 06:33 AM   #20
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Sure glad I didn't jump on the Smart plug bandwagon ...guess "smart" is in the eye of the beholder.

I have had several plug meltdowns but in the end...vigilance and maintenance are the best deterrents to electrical issues.

Ditto here. Salt and other factors are the real problem, and I don't think a SmartPlug is immune to, or can vanquish any of that. I'm sticking with my NEMA std twistlocks, and inspecting them regularly. They have failed, and will fail again. The trick is inspection and catching it early.
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