Melt Down Anybody??

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.

Delfin said:

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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the light glass or the 26 watt element at white hot temp?

or something in between...

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.

boatpoker said:

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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Is that kind of setup ABYC compliant?

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.

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 .

FF said:

Even a slow blow fuse will be many times faster than a CB .

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Also more repeatable IMO from what I know about circuit breakers.

psneeld said:

the light glass or the 26 watt element at white hot temp?

or something in between...

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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.

Delfin said:

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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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...

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.

Edelweiss said:

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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I'm not sure never is the correct word...but exactly my experience too...

So what do we do in the meantime while the manufacturers and marinas dance?

I have a question???

This is for folks that have examined these burnt connectors, both the smartplug and the NEMA kind.

Is the heat source generally isolated to one conductor?

Or is the heat source more than one conductor?

The ones in the photos of the smart plug clearly show one conductor heating from the photos. This would indicate a high impedance in the current path, generating the heat. IE one bad connection.

If the heat source is two of the three conductors then you could still have high impedance connection(s), or you could have a hot to neutral (or ground) fault.

So, which is it guys, one terminal melted or two?

Northern Spy said:

Looks like a loose neutral wire connection to me.

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X2. High resistance on the white wire terminal caused excessive heat, not overloading. Either loose or corroded. If it was overloading, there would also be heat damage on the black terminal. High resistance faults will not trip a perfectly set breaker until the cable faults to ground somewhere. You can make a DIY arc furnace the same way with a pair of carbon rods and an iron. Put the rods in series with the load touching their tips together.

Earlier in the thread a poster mentioned a loose return leg getting hot. That was a good observation, loose connections will burn quickly. Vibration and stress can loosen things up.
If anyone wants to try something for a permanent fix, look up 'potting compound'.
In the Air Force we potted plugs that were susceptible to moisture or vibration. Then you would only have to worry about overloads.
A boater could buy a good quality plug, assemble it correctly, tighten everything up, test it, then pot the hell out of it. A soak in MEK (methyl ethyl ketone) will melt it away for replacement or repair.
Just thinking outside the box a little bit.

ksanders said:

I have a question???

This is for folks that have examined these burnt connectors, both the smartplug and the NEMA kind.

Is the heat source generally isolated to one conductor?

Or is the heat source more than one conductor?

The ones in the photos of the smart plug clearly show one conductor heating from the photos. This would indicate a high impedance in the current path, generating the heat. IE one bad connection.

If the heat source is two of the three conductors then you could still have high impedance connection(s), or you could have a hot to neutral (or ground) fault.

So, which is it guys, one terminal melted or two?

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I wouldn't bet a ton of money on it..but my experience would have to say I have seen pretty equal amounts of overheating either one or both hot/neutral prongs..

psneeld said:

I wouldn't bet a ton of money on it..but my experience would have to say I have seen pretty equal amounts of overheating either one or both hot/neutral prongs..

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Since the same current flows through both (unless there's a ground fault), that would be expected.

WesK said:

Since the same current flows through both (unless there's a ground fault), that would be expected.

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?????...maybe I said it poorly but I would say there are an equal amount of plugs out there that one half have one prong burnt and the other half have 2 prongs burnt.

boatpoker said:

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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Hard wiring the shorepower cord will certainly solve plug/socket problems but it will severely limit cruising potential.

Edelweiss said:

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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Aren't there rather a large number of UL listed products that are designed for consumer installation? The idea that UL wouldn't want to list their product on the sole basis that Joe Sixpack installs it seems unlikely.

WesK said:

Hard wiring the shorepower cord will certainly solve plug/socket problems but it will severely limit cruising potential.

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Here's boatpoker's post..

boatpoker said:

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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how would that limit cruising' potential?

Delfin said:

Aren't there rather a large number of UL listed products that are designed for consumer installation? The idea that UL wouldn't want to list their product on the sole basis that Joe Sixpack installs it seems unlikely.

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I don't think that is what they are saying.

Sounds more like Mr. Smith would like UL to approve his plug system and make it the UL standard for boats instead of the twist lock system. Underwriters Lab isn't interested in doing that. I don't blame Mr. Smith, UL endorsement would be a feather in his cap.

The Insurance Company is concerned that the SmartPlug product is targeted at DIY sales, yet it has an inherent DIY flaw. When installed on an old cord by a boat owner, failure to follow the exact instructions will cause catastrophic failure and exposes the insurance Co. to greater risk. That said, one of these plugs was purportedly installed by an electrician??

Until this is ironed out, they would prefer you use the UL approved Marinco twist lock style marine plug system or if you've already converted, inspect and monitor your SmartPlug for problems regularly.

WesK said:

Hard wiring the shorepower cord will certainly solve plug/socket problems but it will severely limit cruising potential.

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If you hardwire BOTH ends, oh yea!

Greetings,
There are many products a DIY person uses that if exact instructions are not followed pose a mild to severe risk. Nothing really to do with the product or an inherent flaw just the end use and application/installation.
Unless any of us have a brand new boat (and even then) we ALL have examples of the havoc the DPO created. I'm sure we've all experienced poorly crimped connectors.
Now, IF the "safety shutdown" part of the Smart Plug is to blame there is indeed an inherent risk.

Does smart plug sell their product already attached to a power cord ala Marinco? If so, what is the cost?

Yes. . a 30 amp, 50' cable with molded plug ends and a bulkhead receptacle is around $300. Look at Amazon.com

Don't believe they make a 50 Amp cord though.

RT Firefly said:

There are many products a DIY person uses that if exact instructions are not followed pose a mild to severe risk. Nothing really to do with the product or an inherent flaw just the end use and application/installation..

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I once watched a co-worker trying to replace the cord cap (plug) on an extension cord. He was cursing because the wires wouldn't stay in the holes and kept falling out. Eventually, I pointed out to him that after inserting the bare wire in the hole he was supposed to tighten the screw.

Anyone who manufactures or sells anything will eventually face a lawsuit by someone who installed or used his product incorrectly and suffered damages.

To minimize the chance of overheating or fires on shorepower cords or fittings:

1) Examine them and replace any that show signs of arcing or pitting.

2) Yes dielectric grease will help to prevent corrosion. You'll have to reapply it periodically.

3) Use your handy non-contact infrared thermometer from time to time to measure the temperature of shorepower plugs and sockets. Do this after a period of high load (heat or AC running). If there is a significant higher temperature than the surrounding area, you have a problem and should take care of it ASAP.

4) A corroded or damaged socket or plug will eventually damage whatever is plugged into it or whatever it is plugged into.

N4712 said:

Don't believe they make a 50 Amp cord though.

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SmartPlug Systems 50 Amp Products

N4712 said:

Don't believe they make a 50 Amp cord though.

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They make the 50 amp plugs and receptacles. But I haven't seen a molded 50 amp cable and plugs yet.

Edelweiss said:

I don't think that is what they are saying.

Sounds more like Mr. Smith would like UL to approve his plug system and make it the UL standard for boats instead of the twist lock system. Underwriters Lab isn't interested in doing that. I don't blame Mr. Smith, UL endorsement would be a feather in his cap.

The Insurance Company is concerned that the SmartPlug product is targeted at DIY sales, yet it has an inherent DIY flaw. When installed on an old cord by a boat owner, failure to follow the exact instructions will cause catastrophic failure and exposes the insurance Co. to greater risk. That said, one of these plugs was purportedly installed by an electrician??

Until this is ironed out, they would prefer you use the UL approved Marinco twist lock style marine plug system or if you've already converted, inspect and monitor your SmartPlug for problems regularly.

Click to expand...

UL determines the standards that apply to a particular product, and then test it to that standard if you pay them to do so. I may be wrong, but I don't UL think ever refuses to determine if a product meets the appropriate standard as Mr Smith seems to suggest. For example, here is a locking plug system that is UL approved that isn't a twist lock: Spec Sheets

Why would UL approve this, and not the SmartPlug unless the SmartPlug fails to meet some UL standard?