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Old 02-12-2014, 07:37 AM   #21
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Of course when a really sensitive breaker is installed ,,folks will be moaning that the air cond blows the breaker every time it cycles on.

Have no idea if it is useful , but I cycle the breaker in a power pole , before pluging in.
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Old 02-12-2014, 07:40 AM   #22
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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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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.
Disagree completely. I believe that the Smartplug is a superior product to the NEMA plug in both design and construction.

An interesting read here.
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Old 02-12-2014, 07:41 AM   #23
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Low voltage will do that - happened to us last year at a state marina. Everyone had air cons running, we were seeing less than 100 volts coming into our boat. Went out to dinner, left our air conditioner on. Came back to a fried inlet that looked just like the one above. CB on the dock never tripped. The Marinco inlet which melted does have a protective housing on the inside, which I assume is to keep the boat from starting on fire. All the melting and burning was totally contained within the housing.
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Old 02-12-2014, 07:43 AM   #24
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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?

Tom
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Old 02-12-2014, 08:02 AM   #25
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Disagree completely. I believe that the Smartplug is a superior product to the NEMA plug in both design and construction.

An interesting read here.
I don't doubt that it is superior in design and construction but they have not eliminated the base problem and who knows what their failure rate is compared to the standard plugs?

My bandwagon comment is typical for any new design or technology...while I may think the direction is good..I may just not think the learning curve for that design/tech is something I want to pay for and live through till the evidence is substantial of certain success.

While compass marine is a great source of info and dynamite site for how to....like Pascoe...not the only expert/professional/hands on guru out there.

I also know there's some REALLY SMART, talented guys with lot's of boating experience on this forum too... ...so I hope never to insult the intelligence of them...

But I am not convinced that the regular twist locks are a huge issue as tens if not hundreds of thousands are used every day and the small number of fires started by them (and many probably really aren't ultimately the plugs fault) tell the tale as well as the issues that people experience with marine CBs and bad power posts.

Which just reminded me....in my experience I would say that 90% or better of the really bad plugs are always at the power post and not the boat. Smart Plug is only boatside for now...correct?

So yes...I would love to see a better product or design...but if my problem is at the other end of the cord...how/why switch until marinas do?
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Old 02-12-2014, 08:43 AM   #26
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Circuit breakers are mechanical devices. That means they wear over time and do not necessarily perform as intended, especially when used as an on-off switch which many people do.
They also are not necessarily manufactured to design specifications. I know this for a fact as I worked for a short time supporting a factory that manufactures circuit breakers. I won't name the company but you all know them and I'm sure they are not alone.
So taking both the above into consideration it is not surprising to me that breakers do not always trip when they should.
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Old 02-12-2014, 08:45 AM   #27
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Circuit breakers are mechanical devices. That means they wear over time and do not necessarily perform as intended, especially when used as an on-off switch which many people do.
They also are not necessarily manufactured to design specifications. I know this for a fact as I worked for a short time supporting a factory that manufactures circuit breakers. I won't name the company but you all know them and I'm sure they are not alone.
So taking both the above into consideration it is not surprising to me that breakers do not always trip when they should.
Nobody likes a voice of reason around here....
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Old 02-12-2014, 10:39 AM   #28
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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.


How many amps, over how much time will it take to burn up #10 wire, and the connectors?
Quite a lot, as it turns out. The ohms resistance/meter of AWG 10 gauge wire is .00328. Current squared times resistance equals watts of heat. 90 amps flowing through 10 gauge wire will generate about 26 watts, equal to the heat output of a refrigerator light, which would trip a 30 amp breaker in 30 seconds or so absent a fault to ground. I assume the damage we see in the picture isn't the result of 30 seconds exposure to a refrigerator light.

Run the same amount of current through a 40 gauge wire with resistance of 3.44 and you can generate about 28,000 watts of heat, which is why if I were to explain what happened here, I would ask the manufacturer what the purpose of the "trip thermostat" they refer to is, since it doesn't appear to do what they say it will do, i.e. provide "Overload Protection - internal thermostat cuts power at the first sign of overheating." Having seen it before I would look to whatever circuitry is involved in the "trip thermostat" since like many electronic components, it ain't using 10 gauge wire.

Not trying to pick on the manufacturer - just questioning the wisdom of placing circuitry that will melt down when exposed to an amp or so of current with a 30 amp breaker protecting it.
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Old 02-12-2014, 10:56 AM   #29
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Had a plug ignite in my hand some years ago. I then hard wired the cord to the boat with proper connections and appropriate strain relief, never had another issue. Fewer connections, no wear from repeated connect/disconnect = Fewer potential problems, makes sense to me
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Old 02-12-2014, 10:56 AM   #30
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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.
The manufacturer is quite right that once the connection point is compromised, resistance can go up sufficiently to cause a melt down without drawing enough current to trip the breaker. That can be from water intrusion, or a loose connection. I guess I just question how much this particular product adds to safety when its installation method appears to be a bit sensitive to operator error, and it utilizes a feature that apparently doesn't work - the ability to shut off current when any heat is present.
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Old 02-12-2014, 11:13 AM   #31
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At about $75 to $90 a pop, a 50 foot, 110V 30 amp cord with properly attached ends can be replaced with a new Marinco very easily if suspect. One's desire to do things on the cheap can get expensive.
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Old 02-12-2014, 11:29 AM   #32
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Quite a lot, as it turns out. The ohms resistance/meter of AWG 10 gauge wire is .00328. Current squared times resistance equals watts of heat. 90 amps flowing through 10 gauge wire will generate about 26 watts, equal to the heat output of a refrigerator light, which would trip a 30 amp breaker in 30 seconds or so absent a fault to ground. I assume the damage we see in the picture isn't the result of 30 seconds exposure to a refrigerator light.

Run the same amount of current through a 40 gauge wire with resistance of 3.44 and you can generate about 28,000 watts of heat, which is why if I were to explain what happened here, I would ask the manufacturer what the purpose of the "trip thermostat" they refer to is, since it doesn't appear to do what they say it will do, i.e. provide "Overload Protection - internal thermostat cuts power at the first sign of overheating." Having seen it before I would look to whatever circuitry is involved in the "trip thermostat" since like many electronic components, it ain't using 10 gauge wire.

Not trying to pick on the manufacturer - just questioning the wisdom of placing circuitry that will melt down when exposed to an amp or so of current with a 30 amp breaker protecting it.
the light glass or the 26 watt element at white hot temp?

or something in between...
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Old 02-12-2014, 11:56 AM   #33
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The amount of metal in the prongs of standard 30. Amp plug is not enough to carry that load continuously. Look at the plugs in rv and house hold worlds they have a lot copper to copper to make the connection. Marine plugs are very disappointing in this connection and are in a much harsher world.
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Old 02-12-2014, 12:36 PM   #34
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Had a plug ignite in my hand some years ago. I then hard wired the cord to the boat with proper connections and appropriate strain relief, never had another issue. Fewer connections, no wear from repeated connect/disconnect = Fewer potential problems, makes sense to me
Is that kind of setup ABYC compliant?
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Old 02-12-2014, 01:09 PM   #35
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Even if it's not....I think ultimately its better....

I've been toying with the idea myself...not sure it's any diff than a Glendenning reel setup....certainly less complicated and prone to failure.
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Old 02-12-2014, 01:33 PM   #36
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The plug shown is from a box store for house use , It and its 50A 240V brother are common in the RV industry.

Never havve seen one melted yet.

Folks that wish to protect their boat , and the power hose, and their inlets can simply install a FUSE box inside the vessel.

Even a slow blow fuse will be many times faster than a CB .
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Old 02-12-2014, 02:07 PM   #37
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Even a slow blow fuse will be many times faster than a CB .
Also more repeatable IMO from what I know about circuit breakers.
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Old 02-12-2014, 02:16 PM   #38
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the light glass or the 26 watt element at white hot temp?

or something in between...
If the wire in a 30 amp cord had the same thermal mass as the filament in a light bulb, it would be the white hot option. Far as I know, 10 gauge is a bit beefier.

Which goes to the point I was attempting to make. A meltdown like this can be caused by some delicate piece of electronics experiencing current sufficient to melt it but not trip the CB, which in turn melts other components, or by a moisture bridge between a live leg and ground occurring that accomplishes the same. Every time I see a device with circuitry that is not separately fused to avoid these situations - especially in a marine environment - I get nervous. The presence of the thermal breaker they talk about, which obviously didn't do its job in these examples, is just such a piece of circuitry that can cause fires without every bothering the CB protecting the line.
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Old 02-12-2014, 02:42 PM   #39
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If the wire in a 30 amp cord had the same thermal mass as the filament in a light bulb, it would be the white hot option. Far as I know, 10 gauge is a bit beefier.

Which goes to the point I was attempting to make. A meltdown like this can be caused by some delicate piece of electronics experiencing current sufficient to melt it but not trip the CB, which in turn melts other components, or by a moisture bridge between a live leg and ground occurring that accomplishes the same. Every time I see a device with circuitry that is not separately fused to avoid these situations - especially in a marine environment - I get nervous. The presence of the thermal breaker they talk about, which obviously didn't do its job in these examples, is just such a piece of circuitry that can cause fires without every bothering the CB protecting the line.
Most of that I agree with and that's why new tech before it's come into it's own in the marine environment is for others...not me...
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Old 02-12-2014, 02:52 PM   #40
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The insurance agent who represents both the effected boaters is in contact with SmartPlug regarding their product failure. Here are a couple of excerpt from that email:

"I received a call from Ken Smith the owner of smart plug. The boat side is never the problem and it is the old cord he said. He is sending me information on this plug system so that I can look it over."

"I was told by Ken Smith that for 5 years he has been trying to get UL to approve the product and make it a standard but they would not listen. My concern is that if they sell you an adaptor that is supposedly something "you" (Joe boater) can install....it should not have so many issues that always seem to point to installation. Both of my clients are astute and I know would have made every effort to do it correctly." . . . "I am doing a seminar on insurance claims and contracts, May 12th here in Anacortes (Port of Anacortes). I have invited the CEO of smart plug to come and defend his product."

If you are interested in attending, the information is on the Port of Anacortes website.
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