smart plug and socket failed

The smart plug and socket started an electrical fire that melted fuse them together. No damage except for the smart plug and socket but a log of smoke damage to the immediate area. The cause was caused the the socket did not hold the plug secure in place. The socket and plug was 240 volt, 50 smp which is heavy. I have had trouble with them before wiggling loose causing the electrocity to go off and on. The dock and house breakers did not trip.

We replaced the socket and plug with the marinco with the convention locking ring we used for 30+ years. Had to replace the wires from plug to breakers. The Eagles and we are well known so the marine electrician came right over and with in 3 hours electricity was back an. He said the smart plug was not that reliable especially the big hravy power cords. To much weight pulling down on the plug.

So you might want to ckeck and/or replace plug and socket.

Ah, progress.

Phil Fill said:

He said the smart plug was not that reliable especially the big hravy power cords. To much weight pulling down on the plug.

So you might want to ckeck and/or replace plug and socket.

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I Ihad a SmartPlug 110-30amp plug for about 5 years & I now have a SmartPlug 240-50amp plug on my present boat. (2 years) I've had exactly "0" problems with either one!

There have been a few smart plug meltdowns.

While I like their idea....it isnt infallible either.

I know some standard 50A plugs have problems, but very few compared to the standard 30A plug.

A great idea that still needs improvement or better exanation of user isdues if there are any.

The traditional style 50amp plug is very robust, I can't see that one having the issues of the traditional 30amp which can easily be pulled out without the ring being used.

Agreed. 50 amp is about foolproof.

The biggest failure I have seen in 50A 125/250V plugs is when the neutral lacks conductivity and starts burning a plug and spikes that fry equipment onboard.

But with regular disengaugement of the plug, it is caught early and corrosion remains at bay.

They've had some significant failures. I think there was a thread on here with pictures posted of Smartplug melt downs.

As I recall, the failure was primarily with updating an existing power cord with Smartplug replacement plugs and receptacles. The plug end relies on plastic teeth to grip the power cord casing to keep the plug from twisting on the cord and shorting the wires. Also the thermal fusing didn't work when that occurred.

The factory molded Smartplug and cord didn't seem to have that problem, but it's a tad expensive.

I had a melt down and never quite figured why as well
Would be grateful for answer. Went down for night all ok in morning plug was in the water all burnt up!!

Interesting. I put a 30 amp Smart Plug on my Sailboat. I have been very happy with it. I think the SmartPlug is much more secure and safer than the standard 30 amp plug.

My North Pacific has a 50amp/125 service. That plug seems extremely secure and I don't feel the need to change it.

I take a simpler approach than many.

I use the standard NEMA 30 amp hardware and use a bit of conductive grease on the terminals.

I also limit loading of the shore power to no more than 80% of the rated capacity, which if memory serves correctly is the NEC continous rating for a overcurrent protective device.

Tootles said:

I had a melt down and never quite figured why as wellView attachment 66140View attachment 66141
Would be grateful for answer. Went down for night all ok in morning plug was in the water all burnt up!!

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Our smart plug was a little worse as we had smoke damage inside and outside with some paint blister. We have a boatnanny alarm that text a status every day at 12 noon. Wednesday text every thing was ok, Thursday no text, so called Everest yacht service to check on. They called about the failure. They said they know of other failure.

The plug has a max of 30 amps per leg, so well within limit.

Phil Fill said:

............. He said the smart plug was not that reliable especially the big hravy power cords. To much weight pulling down on the plug. .............

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I won't get into the argument of "smart plug" vs. a conventional plug and socket, but here is what I do and my suggestion to everyone regardless of the type of plug/socket you are using: Use some strain relief to take the weight and strain off the plug. I have a Velcro strap near the boat end of my shore power cord and use it when I coil the cord to store it. I also use it to strap the cord to a rail near the boat inlet. This takes the weight off the connection and protects against something pulling on the cord from putting strain on the connection. Simple, cheap and effective and works with any brand or size of cord/plug.


BTW: Regardless of the brand or style of plug, make it a habit to feel the outside of the plug after you've been connected for a while, especially if the heat or AC has been running. If it's warm or hot, you have a problem that needs to be taken care of.

Never had trouble with my 30 amp Nema plug style designed in 1938.
Both my 30 amp yellow shore power cords are very old and a prior owner replaced the 4 plug ends on them both using Nema standard 30 amp Hubbell and Marinco plug ends.
The old cords are pretty stiff.

This guy likes the smart plug. I am never going to change to a smart plug.


Shore Power Cords - SmartPlug vs. 1938 Photo Gallery by Compass Marine How To at pbase.com

The smart plugs do have some good ideas in them...
But before I jumped to them, I wanted more power coming to the boat so upgrading to a 50A 125/250 setup made sense.

While they do suffer from corrosion problems, they dont burn up nearly as much as the easy to wiggle loose 30A setup.

The 50A plug has positive lock to the full outlet, not just hanging on the prongs.

Where there is metal to metal socket connection, you could probably hang from it so supporting that type of connection while nice is almost overkill.

This topic always leads to spirited debate.

On the one hand are those who made the switch. Their argument is that it's newer and "better," at least in theory. This argument is bolstered by satisfied customers who report zero problems in their implementation.

On the other side are those who argue against assuming something is "better" just because it's newer or costs more. Used properly and inspected regularly, the old tried-and-true connectors also have millions of users with zero problems.

I lean toward the latter argument. Maybe it's because I'm skeptical when someone wants to sell me something that requires replacing millions of installed and working non-proprietary components with their patented new stuff.

To me, a "smart" plug would be one that's safer, but still works with existing installed equipment.

I also know that, once a consumer does buck tradition and pay extra for a new product, they're highly motivated to justify that decision by showering praise on it. I'm not trying to cast aspersions on anyone here; I do the same thing. Just that it makes it hard to get unbiased feedback.

However, multiple, actual reports of fires caused by these proves to me they're not quite as "smart" as the marketing suggests. Before I throw away thousands of dollars' worth of cables and dockside connections I already own, you have to convince me that the replacements are significantly better.

Extraordinary claims require extraordinary proof. These fires aren't helping that.

Agreed. People tend to want to justify what they have invested their money in.

I usually don't take an owners opinion of a product that he owns but if he no longer owns the product, boat, electronic equipment I value that opinion higher.

Many people have pointed out that the old NEMA 30A leaves a lot more room for improvement than the NEMA 50A plug. The 50A plug is very robust with a large supporting shell, large contacts, and positive lock.

So there is a very different, and better argument for the Smart Plug as a 30A replacement, and much less so for a 50A replacement.

I don't doubt that the Smart Plug 30A is an improvement over the NEMA plug, but I think that this thread and others demonstrate that the Smart Plug is not infallible as many would like to believe it is.

My boat uses two 30 amp inlets, one for air conditioning and heat, the other for everything else. On the A/C and heat there was some melting of the plastic on one of the pins of the NEMA plug male and female. I had read good reviews of the Smart Plug so bought a 30 amp inlet and cord to give it a try on the A/C & heating circuit. I have installed it but we haven't been able to get out on the boat to use it except for a trial at the dock. I'll be able to try the A/C, if only at the dock, this summer. I'll keep a close watch on it and report any problem. Heating is the bigger draw in my system, I sure won't be needing that till winter.
I have an IR thermometer so will keep that and fire extinguishers close by.
Picture of the inlet and plug, the cord and plug were not very old and have never been in the water.

What would be considered a dangerous temperature at a 30 amp inlet?

Whether or not you have a smart plug or the old fashioned kind, starting with either in good serviceable shape, the single biggest problem with a 30 amp service is the load. I'll bet that the vast majority of boats plugged into 30 amps (3600 watts nominally) are overloading the circuit. Battery charger, hot water tank, heaters, lights, etc. 30 amps, allowing for 90% safe loading is only 3240 watts. A heater is 1500 and a water heater is the same, with a couple of lights on, that's it! Do you have your battery charger on? Do you use the water pump? A toaster or coffee pot? Air conditioning? Is your wife using her hair dryer?

I have found that a very good test of your maximum load, besides feeling the plug itself for warmth, is to monitor the voltage. If you dont have an AC meter on board, plug your digital multimeter into a socket - if it is anything less than the marina supplied voltage with no load, you are exceeding the design load. In our marina we get 118 volts no load - that is the absolute minimum I should see with a load. Anything less than that and the weakest link, the shore power plug, will overheat and fail and possibly catch fire. Circuit breakers are not designed to shut off a gradually applied overload, they are designed to react to a short circuit so breakers will not save you!

While I agree with the above...I think the double whammy with traditional 30 A plugs is that they easily become loose and arc and spark, with or without high loading.

So if one day it is one thing and the next the other, their early demise is inevitable.

On many I see putting which to me means looseness arcing, but almost certainlt the 2 30A lines where one runs several air conditionets, that baby cooks regularly.

psneeld said:

While I agree with the above...I think the double whammy with traditional 30 A plugs is that they easily become loose and arc and spark, with or without high loading..

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That was the main thing on my mind when I switched to a SmartPlug years ago. That, and the hassle of trying not to cross thread the ring when plugging in to the boat. I've always felt that the threads on the old style are too fine. As I posted earlier in this thread, I have a 50 amp plug that when it's plugged in you can almost tow the boat with it.....it's really secure!

An old thread, but worth a re-reading.
In 2011 I put in a 30 amp Smart Plug, replacing the original (1980 so over 30 yrs old) Marinco plug. No sign of weakness on the Marinco, but my survey, required by my insurance renewal, recommended the change.
Over the last couple of weeks, out cruising, so frequent visits to different docks, and the power inside became intermittent. Yesterday the frequency of off was much higher than on, so I went looking for a solution. I pulled off the boat end and put a meter on the female terminals. all were good, both in voltage and appearance. I next undid the boat end, pulled off the connections and re-installed the old Marinco connector. Inspection revealed nothing obvious.
I have had continuous power now for almost 24 hours, so the failing was at the smart plug, male end.
I think I will stay on the 30s technology, but monitor it.

There was an upgrade to the early Boat side socket that had a thermal breaker in it that would kick off, or eventually fail randomly. ABYC did not like that it came back on randomly. Smartplug will send you a retro fit kit with new boat side socket and plug innards to fix this issue at no charge (at least they did for me and a buddy after we experienced the random failures.)

I never imagine going to theat 'smart ' plug thing. I have twin 30, I would go to standard 50 single plug, if I did anything which I won't. Who like dealing with 2 cords and 4 plugs?

I also don't bother with the second 30 amp cord set. I got this way ldue to other marinas only ever having one outlet per slip, so I suppose I was trained this way... Current marina does have twin 30 amp power.

I used a 30 amp double pole switch and joined both 30 amp lines into one inside the boat for convenience sake. Have not had any problems yet. But I also do not run all sorts of heavy loads. I leave the hot water heater off all the time, dont need it ever. The biggest load is the MW oven, 14 to 15 amps running. The cruisair is 10 to 12 amps depending on temps, I tend to also not use it much. We almost never use the princess stove. And don't use the 2 onboard electric built in space heaters.

Doing a test, it took 27 amps load to blow open a 20 amp breaker, and worked for a few minutes, so a 30 amp cord and breaker might take almost 39 amps before opening the circuit. It does eventually heat up with enough time to open circuit with less amps.

I suspect any problems with the Smart Plug are caused by not inserting the connector fully into the inlet. When fully inserted there are two spring loaded clips that engage the inlet fitting and the inlet cap comes down and engages a stud molded into the top of the connector. When all of these are engaged, it is very secure.

Keith, this is Terry with Smartplug. Please give me a call at 206.285.2990. Thanks!

HopCar said:

I suspect any problems with the Smart Plug are caused by not inserting the connector fully into the inlet. When fully inserted there are two spring loaded clips that engage the inlet fitting and the inlet cap comes down and engages a stud molded into the top of the connector. When all of these are engaged, it is very secure.

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What happens if the end of the smart plug falls into salt water. Seems like it is as susceptible to corrosion as any other plug. Someone might drop it in the water, not rinse and dry it, just plug it back in wet. That ought to cause it to fail, user error.

Phil Fill said:

Our smart plug was a little worse as we had smoke damage inside and outside with some paint blister. We have a boatnanny alarm that text a status every day at 12 noon. Wednesday text every thing was ok, Thursday no text, so called Everest yacht service to check on. They called about the failure. They said they know of other failure.

The plug has a max of 30 amps per leg, so well within limit.

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Did boat nanny fail to alert you because loss of shore power?