Smart plug melt down

[O C Diver]

While you never know what the real story is, here is my take. What we know for certain is two 30 amp shore power cords were connected through a Y connector to 50 amp service. We also know the Smart Plug cooked off. Beyond that we don't know if the plug had water in it (or was staged). We don't know if the power on that circuit was off, running the reverse cycle air conditioning and or more stuff equal to or slightly more than 30 amps. We also don't know the quality of his installation of the Smart Plug. I could see a terminal not being tight enough, causing arching and the melt down. I also find it troubling that for all the detail and BS in the video, there was no close video examination of the cord terminals and no examination of the Smart Plug receptacle on the inside of the boat.

Probably none of this matters as the video is probably leverage to get replacement components from the manufacturer.

I know, I'm being cynical.

Ted

 

[rslifkin]

While you never know what the real story is, here is my take. What we know for certain is two 30 amp shore power cords were connected through a Y connector to 50 amp service. We also know the Smart Plug cooked off.

And we know that most Y adapters for that purpose don't have breakers, so depending on what failed, it's possible the 30a cable and plugs were overloaded, as they weren't properly protected by a breaker.

 

[SteveK]

The Glendinning cable system is hard wired. You would still need a breaker within 10’ if I read the guidelines correctly.

I guess I was wondering if I could eliminate the plug, 10 feet, nope as I planned to run from the bow under pulpit back to salon door area panel. Stay with plug, but maybe move it to a better location.

 

[SteveK]

You are correct, 10' of cable length.

But my thought was take the 50 foot cord end hardwire to panel with about 25 feet inside. If I can have 50 feet of cable outside then why can't I have have 25 feet of it inside and 25 feet outside if there are no connection points, the cable just goes inside hardwired to panel.

 

[Bacchus]

But my thought was take the 50 foot cord end hardwire to panel with about 25 feet inside. If I can have 50 feet of cable outside then why can't I have have 25 feet of it inside and 25 feet outside if there are no connection points, the cable just goes inside hardwired to panel.

You can have 25 ft inside but you need a breaker within 10 ft of where it enters if you care about ABYC.

 

[Alaskan Sea-Duction]

Wasn't this the cause of the diver boat in SO Cali

No, the dive boat was anchored and not plugged into shore power. They think it was portable batteries being charged in the main salon, maybe.

Well dumby me!! I thought we were talking about an electrical strip with a bunch of "smart" phones plugged in to it and that is what caused the fire.

Never really cared for the "smart shore power" plugs.

 

[FF]

"Never really cared for the "smart shore power" plugs."

The range plugs and sockets from any big box store are rated 240V 50A and seem far superior to the boaty stuff.

The smaller 120V 30A are good too.

The large blades can be cleaned with an abrasive pad and are self wiping in use.

Most dock power poles have a cover so are kept out of the rain .

These seem to be rated for their full listed amperage not 80% so work well for winter liveaboard with electric heat.

The RV units cost no more than home range units and have a handle to assist pulling the plug.

Under $20 at home depot or your favorite shop.
50-Amp Power Grip Replacement Male Plug

by Camco

 

[Codger2]

On my boat the smart plugs are inside the stern behind a door so they never see any water.

My boat came from the manufacturer with a SmartPlug plugged in to the helm cabinet. I have often wondered why Duffy did this but I have never asked. Since many Duffy owners are over 70, they might forget to unplug the shore power cord from time to time and this lnside hook-up may remind them to do it. (It also is very well protected from rain & boat washer water.)

 

[syjos]

Never really cared for the "smart shore power" plugs.

I never felt that Smartplug was necessary for safety if the Marinco connector is kept clean, secured at the boat end with the lock ring and not subject to excessive amperage.

The current Marinco lock ring uses tabs instead of fine threads making it easy to secure. With the lock ring tightened, there is no movement of the connector.

The original Smartplug was equipped with a thermal breaker that shut off power when the connector reached 200 degrees. Smartplug discontinued the thermal breaker shortly after introduction. I would switch to the Smartplug if it still had the thermal disconnect.

Having my shore connector mounted to a metal box is my insurance if the connector experienced a meltdown.

In over 35 years of using the Marinco connectors, I've never experienced a burnt plug. I do replace the shore cords every 5 to 10 years for cosmetic reasons, when they look dirty.

 

[DDW]

While my post (about use around water) was meant somewhat in humor, I still question the logic and engineering of those who blame water intrusion. That cord seal isn't going to ensure against water intrusion, no matter how installed. Further, it should work soaking wet (at least in fresh water). Imagine an extension cord used in the rain on a construction site, as is done millions of times every day.

Perhaps the insulation of the wires was already brittle from the original melt down, and the wires touched. That seems more likely than a little rain water.

 

[Xsbank]

It was overloaded. Simple. Full of water maybe but that was not the problem.

Dielectric grease for sure, conducting grease never unless you want to blow yourself up.

Smart plug abandoned the thermal thing because they had huge numbers fail and caused more trouble than they were designed to solve.

A breaker may not save you from an overload. They are designed to protect from shorts, NOT overloading. Granted, if it heats up rapidly the breaker may pop but don't count on it. Measure your load! It's really easy, just plug your multimeter into a handy socket. If the voltage is less than you see at the pedestal, you are overloaded for that supply, you are attempting to use more power than is available and you are courting an electrical fire and the possible loss of your boat. Unplug the heater or the toaster and see what the meter does. No matter how you connect to the shore, an overload will find the weak link. 30 amp services are barely adequate for a boat; you have about 3000 watts available safely and that's it! Try it next time you are on the boat and feel if the cord is warm when you walk up to it

K.I.S.S.

 

[TWedd]

XS
Why do you say breakers don't provide overcurrent protection?
That is exactly what they do, prevent the wiring from being exposed to excess current. Yes, a direct short will cause excesss current tripping the breaker.

 

[boatpoker]

XS
Why do you say breakers don't provide overcurrent protection?
That is exactly what they do, prevent the wiring from being exposed to excess current. Yes, a direct short will cause excesss current tripping the breaker.

XSbank I believe is referring to heat. If you run a 30amp cord at 30 amps for very long it can melt without tripping a breaker.

I would not use shorepower without a volt meter and ammeter. We never draw more than 25amps max on either of our two 30amp cords

 

[Comodave]

Actually Smart Plug stopped putting the thermal cutout in because of ABYC recommendations. The thermal cutout would stop current flow and then when it cooled down it would reset automatically. That was seen as a safety issue since you could have it cutout and then start working on the wiring and have it reset while you were working on the wiring. And the circuits could become energized without your knowledge and electrocute someone.

 

[Xsbank]

Sorry, slow to respond.

I didn't say that, I said they may not protect you from an overload. The breaker is there to protect the circuit, not the device, if the wiring is undersized or there is a poor connection, the wire fails before the breaker trips.

Say you overload by 500 watts, you will feel the cable getting warm. Why hasn't the breaker tripped? Because the wire is heating and absorbing the load. Just walk the docks and every warm cable is an overload. Their breakers didn't trip. If you load your circuits to the tripping point and consider that a good indication? Don't blame the failure on the old-tech shore power plug, the blame is squarely on you.

By the way you Glendinning users, I'm sure you are aware how a toaster works, with coils to produce heat? Guess what you have on that spool if you don't unroll the entire cable when you plug it in? Same reason why you never use an extension cord that is still coiled. In your case, the breaker should be installed right at the cable-winding thing.

By the way, Smart Plugs were named that because their original design contained that thermal thing, which was an attempt to fix a problem that doesn't exist. The idea was that the thermal thing would disconnect an overload that was heating up the wires. That device was a failure and actually added to the smoke events so it was discontinued. They are now trying to trash the Marinco type plugs as old school and are marketing their plugs as better connectors. That may be true but there is nothing wrong with the old style (RT that reminds me of beer for some reason). A heated plug is an operator error; in some industries, called "pilot error."

Boat poker, that is exactly the proper way to run shore power and what I've been ranting about for so long.

 

[TWedd]

XSbank I believe is referring to heat. If you run a 30amp cord at 30 amps for very long it can melt without tripping a breaker.

If a 30 amp cord overheats and melts at 30 amps without tripping a breaker, there was a problem with the cord, too much resistance causing excess heat. This usually happens at a connector, this applies to all electrical circuits, not just boats. This is why I try to avoid running electric space heaters on high power setting even in my former dirt homes. Too many connections in a typical daisy chain of outlets to suit my comfort level.

I would not use shorepower without a volt meter and ammeter. We never draw more than 25amps max on either of our two 30amp cords

I agree this is a sensible way to reduce the risk of electrical melt downs. However, I submit that if a poor connection would fail at 30 amps, it would probably fail at 25 amps eventually. I would not let the fact that I was at 25 amps to keep me from regular inspections of my shore power cords and connections as well as the boat wiring panels.

 

[TWedd]

If a 30 amp cord overheats and melts at 30 amps without tripping a breaker, there was a problem with the cord, too much resistance causing excess heat. This usually happens at a connector, this applies to all electrical circuits, not just boats. This is why I try to avoid running electric space heaters on high power setting even in my former dirt homes. Too many connections in a typical daisy chain of outlets to suit my comfort level.

Sorry, the above were my words, somehow I included them as a quote from the previous poster.

 

[tiltrider1]

I agree this is a sensible way to reduce the risk of electrical melt downs. However, I submit that if a poor connection would fail at 30 amps, it would probably fail at 25 amps eventually. I would not let the fact that I was at 25 amps to keep me from regular inspections of my shore power cords and connections as well as the boat wiring panels.

I believe BP was referring that a 30A marine plug run at 30A continuously will fail. They are rated for max use of 30A not continuous use of 30A. You might go a month, maybe 3, some a year but eventually you will have a meltdown.

 

[Xsbank]

You can lead a horse to water...

If you didn't ever change the oil in your engine and it failed, would you blame the engine?

You are supposed to maintain your sh*t.

If you overload and your plug fails, that is a defacto circuit breaker. You might have just dodged a bullet. Blaming the failure on the plug is moronic. If you have a better plug or are hard wired and you still insist on overloading, something in your boat will fail and there is way more stuff inside your boat that will burn much better.

I'm done with this.

 

[boatpoker]

I agree this is a sensible way to reduce the risk of electrical melt downs. However, I submit that if a poor connection would fail at 30 amps, it would probably fail at 25 amps eventually. I would not let the fact that I was at 25 amps to keep me from regular inspections of my shore power cords and connections as well as the boat wiring panels.

Having had Marine Electrical Certification (now retired) I am aware.

 

[koliver]

Those of you who have a Smart Plug with the thermal break thingy, when it fails, they will send you a replacement plug made without the thermal thingy, free of charge, shipped to your free.
I found this out when mine failed and I phoned them.

 

[DDW]

It was overloaded. Simple.

So we do not believe the Youtuber's claim that the circuit that failed was unloaded?

 

[rslifkin]

For those saying that any cord or connector that's warm is overloaded, that's BS. If you're running the parts near their max rating, they'll get warm. Not hot, but warm. If you're working them hard and there's a bad connection, then things can get hot quickly. This is where a breaker won't save you. It'll protect from an overload, but not from overheating below rated load due to damage or corrosion causing more than normal heat production.

 

[markbarendt]

XSbank I believe is referring to heat. If you run a 30amp cord at 30 amps for very long it can melt without tripping a breaker.

I would not use shorepower without a volt meter and ammeter. We never draw more than 25amps max on either of our two 30amp cords

That’s good practice. Fuses and breakers are there to avoid catastrophes not to act like a speed limit sign.

The typical standard for a fuse is roughly 125% of the greatest expected load.

Apply that same logic to a breaker and your 25 amp rule is darn close to the design load.

 

[markbarendt]

For those saying that any cord or connector that's warm is overloaded, that's BS. If you're running the parts near their max rating, they'll get warm. Not hot, but warm. If you're working them hard and there's a bad connection, then things can get hot quickly. This is where a breaker won't save you. It'll protect from an overload, but not from overheating below rated load due to damage or corrosion causing more than normal heat production.

Um, no.

https://www.reference.com/science/temperature-affect-resistance-wire-d6433c07cb126694

As wires get warmer and warmer they become less conducive. The source of heat doesn’t matter in the equation.

I’d suggest though that if the heat is noticeable and generated by the current in the wire it is becoming a problem.

 

[rslifkin]

Um, no.

https://www.reference.com/science/temperature-affect-resistance-wire-d6433c07cb126694

As wires get warmer and warmer they become less conducive. The source of heat doesn’t matter in the equation.

I’d suggest though that if the heat is noticeable and generated by the current in the wire it is becoming a problem.

Yes, and that's why once things get hot, they typically get worse quickly. But for a 30A shore power cord with 10ga wire, the cord being slightly warm to the touch (~10 degrees above ambient temp) is normal if you're pulling close to 30 amps through it. If it's significantly warm, there's a problem.

 

[syjos]

You can lead a horse to water...

If you didn't ever change the oil in your engine and it failed, would you blame the engine?

You are supposed to maintain your sh*t.

If you overload and your plug fails, that is a defacto circuit breaker. You might have just dodged a bullet. Blaming the failure on the plug is moronic. If you have a better plug or are hard wired and you still insist on overloading, something in your boat will fail and there is way more stuff inside your boat that will burn much better.

I agree 100%

Shore power cords and plugs need perodic maintenance, just like everything else on a boat.

Expecting Smartplug or some other device to make up for lack of maintenance is foolish.

And the blades on a Smartplug need cleaning also.

 

[syjos]

Relying on analog AC amp and volt meters is iffy. How many boaters calibrate them? Most adjust to the zero but not at higher current or voltage.

Most analog meters are not accurate either. Their readings are not linear so only accurate at certain readings. And accuracy depends on the meters size and spacing of the marks.

Digital amp and volt meters are accurate and a lot easier to read.

I have several Blue Seas 8247 Digital Multi Function meters on Sandpiper. They display current, frequency, power and voltage. There are alarms for high current and low voltage.

 

[GoneFarrell]

What I've seen too many times is that the plugs are at an angle in the sockets due to weight of wire or getting tugged as the boat moves in moorage.

The misalignment means poor contact, heat, then the smoke gets let out of the wire and connectors.

 

[DrissZougari]

This failure was not caused by water intrusion since the pedestal breaker did not trip. the video shows a charcoaled connector due to heat. we have to keep in mind that, it looks like the boat is under shrink-wrap and the owner must have extra heater(s) added to the boat current load. I believe that the current draw of the boat was closer to 30A (breaker trip level) for a longer period causing the smart plug to heat up and melt (it take time heat up a boat) .