In today's day and age it is far and few between that I come across products that:
Do as they say.
Are built to an exceptional standard.
Redefine what great is.
The SmartPlug, IMHO, is one of these products.
I got a call from this owner one day saying his shore power cord looked "charred" and no surprise it certainly was. I knew exactly how to fix and remedy his problem, a new SmartPlug inlet and cord set..
Unfortunately this call was in February, in Maine and the boat is stored in the water because this hearty owner sails year round!
Due to the fact that he sails year round he keeps his boat heated with electricity to prevent it from freezing up. I had previously warned him that we would want to beef up his shore connection and cord to which he shrugged and put it off.
A few months later my suggestion became an emergency...
Pictured here, in the snow, is a 50' X 30A SmartPlug cord set and a 30A X 125V AC inlet.
No Mincing Of Words Here
This is an ordinary day for me and it brings to mind that saying, a picture tells a thousand words...
OK more ranting from me, that you've come to expect.. Here it goes.
AS A MARINE ELECTRICIAN I TRULY DISLIKE THIS ANTIQUATED & UNSAFE STANDARD FOR SHORE POWER PLUGS/SOCKETS ON BOATS!!!!!!
The regulatory boards that over see this such as the NEC, NFPA & ABYC should all be ashamed that they continue to allow this unsafe standard to continue.
There I said it.. Whew..... Why do I dislike it so much? Lets examine this further.
-When this plug standard began life it was back in 1938! I can't imagine that Harvey Hubbell III ever intended this to be used on boats near the ocean back when it was conceived..
-In 1938 houses had cloth covered wire and no safety ground for 120V outlets
-In 1938 we did not even have seat belts
-In 1938 GFCI outlets were not even a thought in an inventors mind
-In 1938 lead paint was the rage and asbestos was in everyday use.
-In 1938 there were no standards for electrical safety on docks or boats.
-In 1938 safety testing for marine use never even existed.
-How many other electrical items do you use in your house or boat that have remained virtually unchanged since 1938..????
Suffice it to say we have been grandfathered into a substandard and completely inadequate plug & socket combination for marine shore power cord/plug/receptacle use. This twist-lock standard would never gain approvals under today's electrical safety standards. Never!
High Resistance Is Your Enemy
"But I have a circuit breaker aren't I protected?
With this old antiquated left over 1938 NEMA L5-30 standard there is approximately 20 times less surface contact area than there is in a modern SmartPlug. Twenty times less contact area!!!!!
On boats we are in a corrosive environment, that also moves! Add just a little corrosion, some torquing & pulling on the plug and stack all that onto the minimal contact area and we have heat.
Heat is generated at points of high resistance in an electrical circuit when pushing current.
Please understand that you can easily start a fire with high resistance and never trip a circuit breaker.
As we can see in this photo the wire was not only corroded, due to marine environment and the age, but it also suffered due to the high resistance. The wire jacket itself was melted and then the jacket fractured.
Here is a prime example of where tinned marine wire may have bought this owner more time. A new run of 10/3 triplex wire was in order. The black oxidation on this wire can also create high resistance. When in doubt it is best to also replace the feed wire from the new AC inlet to the AC panel..
If your wire run between the AC shore inlet to the AC main breaker, at the AC panel, is more than 10' wire feet, not as the crow flies, then you will want to install a second 30A or 50A double pole breaker. This breaker needs to be interrupting WHITE/NEUTRAL & BLACK/HOT, and be located quite closely to the AC shore inlet.
Why Do I Want A Smart Plug?
Over the years I have seen far too many examples of situations like this. I suspect a large number of the 55% of boat fires that are electrical in nature (source ABYC data) are the result of this antiquated and unsafe twist-lock standard we currently use.
Read on and I will dig much deeper into the why's & how's...
Need More Convincing???
When word got out, in my Hall of Fail
article, that I was a huge fan and proponent of the Smart Plug images came flying in from all over of burned twist-lock plugs. I am certainly not alone in my dislike for this antiquated & unsafe standard..
I have far too many images of burned twist-lock plugs to show them all so I chose this one to be a good representation.. A surveyor on the west coast was kind enough to photograph a great collection of them!!
Photo courtesy: A. Mazon
Early Signs of A Potential Fire
If you know what you are looking for the early signs of high resistance can be pretty obvious. Look at the pin closest to you and you can easily see the melted plastic migrating up from the base. There are also signs of arcing and burning on the pin itself.
If your your cord looks like this it is time for a replacement...
It is important to understand that I am not alone in my feelings about shore power safety. The quote below comes straight from ACE Insurance one of the nations largest underwriters of marine insurance. They understand these problems because they pay the claims...
Quote: Ace Insurance Group - SUGGESTED ELECTRICAL INSPECTION STANDARD FOR MARINAS AND YACHT CLUBS:
"Each vessel’s connection devices shall be inspected annually. Annual inspections shall be carried out between the end of the cruising season and the beginning of cold weather, when most boats have returned to their moorings, but before they have begun to present winter heating loads to the Marina. Any boat that enters the marina under a new Moorage Agreement during the winter heating season shall be inspected within 15 days of its entry into the Marina.
A major reason for this inspection routine is to document the condition of each boat’s Inlet Receptacle, the device on the boat’s exterior to which the shore power cord is connected, and the condition of the mating end of the cord itself. This cord-to-boat connection is subject to wear-and-tear damage from the activity of connecting and disconnecting the cord, and it is also subject to damage from wet winter weather, and it is a major source of fire in marinas. If the connection between the cord and the boat is even slightly damaged, it will create heat that can eventually result in fire."
A NEMA L5-30 Socket
In order to dig deeper than we've ever seen before, into this piss-poor standard, I bought a NEMA L5-30 socket. This is the standard used for 30A shore power, on boats, here in the USA and elsewhere.
In order to drive this home I chose to destroy this socket by cutting it open to give a full look into why they are so dangerous.
A "Marine" NEMA L5-30
Other than a yellow color and some tinning of the socket contacts a NEMA L5-30 is a NEMA L5-30.. They are built to the NEMA L5-30 standard whether you buy marine or RV sockets they must all work together.
I Cut The Plug Open And Exposed The Actual Sockets
My goal here was to show exactly why this standard results in so many fires. In this picture we can see the contact area between pin and socket. Not much..!! The green headed screw is the GROUND terminal but they all have about the same contact surface area.
The Locking Dimple
Here you can see the locking dimple on the female socket that locks into the hole on the pins of the male plug. Why is this important?
Socket Riding On Spot Dimple For Contact Area
This is the result of just 1-2mm's of movement and the dimple riding up and out of the hole in the pin..
Let's look at some of the major issues with this standard that lead to safety issues.
Round plugs need to twist in order to lock into place. To facilitate this locking dimples are used to create the detent so you know the socket is in place.
Due to the fact that this standard relies on twisting to lock the plug into the socket the fit of the round plug into the female socket is more sloppy than it should be and allows movement between socket and plug. Shore cords weigh a lot and the cord alone can cause strain to the plug & socket, forget waves, boat movement or people stepping on the shore cord etc.... It is very rare that a shore cord is properly supported to strain relieve the plug & socket.
We are trying to use this on boats and boats move..!
Even just 1-2 millimeters of movement between the plug & socket can cause the dimple to ride up out of the hole and create even less contact area than this already unsafe standard has.
There are no seals on this standard thus it is very easy for corrosion to set in on the pins & sockets and create even more resistance.
The socket clamping mechanism/spring clamping feature is made from material 1mm thick! It does not take much pressure to loosen a 1mm spring clamp.
There are no thermal breakers in these plugs or sockets thus over heating, due to high resistance, will lead to a fire or damn near..
We All Know Boats Don't Move......Right..?
I sure wish I could say I never see this, but I see it with regular frequency.. Scary stuff!!!!!
Actual Contact Area NEMA L5-30 Socket
I needed a good way to show the actual contact surface area of the clamping socket on a NEMA L5-30. I grabbed some sheet metal the same thickness as the plug pin and inserted the socket over it. I then slid it back and forth thus creating a corresponding mark on the sheet metal showing the actual contact area. The results were, well, shocking!...
It should be noted that this was not the dimple side but the non-dimpled side.
I Was Being Kind Here
In the shop shooting these pics I realized my glasses were in the house. When I blew up the picture I realized I had been very kind to the width of the contact surface area. Still 1.31 mm is pretty weak for 30A of current on a moving boat where corrosion is a huge player.
My Computer Seems To Be Taking Over
Really, I am not uploading these, my computer is just so full of them it keeps puking them out... (grin)
McCotter's Marina Fire
During the course of my research I came across the McCotter's Marina fire that happened in January of 2011 in North Carolina. Results on google were inconclusive other than to say the cause of the fire was "electrical". Frustrated with the investigation follow up I could find on-line I reached out to the Bunyan, NC fire department to see if they had any more information, they did.
What I was told was that the "exact" cause can't be 100% pin pointed and they rarely are. Their best guess and best information came directly from an eye witness who had stepped off his boat and saw the fire engulfed on the outside of another boat at the SHORE POWER INLET.. :doh:
The individual I spoke with at Bunyan Fire Department asked not to be identified because they were unsure if the damage numbers on boats, $$$ etc. were accurate. This individual was directly involved in the investigation and quite confident about the eye witness and the perceived or assumed cause of this massive fire and where it originated..
This fire at McCotter's Marina was estimated at approximately 23 million dollars in damage and included a Bertram 68, with a single boat value into the millions. This fire also turned McCotter's into a Superfund Site for clean up. Over 20 boats and the marina were destroyed all on what is believed to be a shore power cord/inlet!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Image Courtesy: Beaufort County Now
This is an actual video that was posted on YouTube of the McCotter's fire. Think about this the next time you need a shore power cord!
Okay, Back On Track....
The contact area that was scored into the sheet metal was just about the same width as a US dime as seen here..
But Wait There's More.....
Never being satisfied with what should be enough to show boat owners what I am trying to say, I pushed on.
This time I aligned the socket with a straight edge and moved it in and out to score another line onto the sheet metal. I wanted to see if this motion created any more contact area or width. It would only be fair to show both..
HOLY COW !!!!!!
I am beginning to see the reason why so many of these plugs and sockets lead to melt downs, boat fires or entire marina's burning down. The entire contact area here is but a 1.3mm X 1.3mm area often trying to handle 25A - 30A of current.
Why Is There So Little Contact Area..???
Remember this is called the "twist-lock" or "HUBBELLOCKź" standard. It requires both inserting & twisting.
Because of this dual stage insertion method the socket receptacle has to be shaped to accept both forms of engagement. INSERT and then the TWIST.. The two contours needed to allow INSERT & TWIST create a very small point of final engagement!
With the last two images you can easily see why the two actions required for connecting this plug, insert & twist, leaves us with very, very, very little contact surface area..
The Spring/Clamp Mechanism
I very often come across sockets where the detent or dimple & hole really don't feel as if they have meshed up and locked into one another. I have learned over the years that this is due to the clamping mechanism in the female socket weakening over time and getting loose.
This weakening is likely exacerbated by movement in the cord and plug as the boat moves. It may also be due to the rather thin metal used in the clamping mechanism of the socket?
As you can see here the metal used to create the clamping force on the male pin is a mere 1mm thick in the NEMA L5-30 socket...
The Male Pins Are Thicker
Here I am measuring the pin thickness of a NEMA L5-30 "marine" plug made by Marinco. It measures about 1.77mm thick.
An RV/Home Depot L5-30
Here is a different brand of NEMA L5-30, a non "marine" version, and we can see that the thickness of the male pin is virtually the exact same. Why is this? Because marine or not these are all built to the same standard. The only differences, when it comes to contact area & clamping force, are usually in the tinning of the terminals on "marine" plugs & receptacles.
Let's Examine The SmartPlug
This is the back of a SmartPlug 30A inlet. This is the original style plug which has now been updated, and further enhanced for ease of installation, but the basics are the same.
In order to wire the AC shore inlet you will need to first remove the rear cover plate. This is a simple one screw deal. Once the plate is removed the inlet can be wired.
This new SmartPlug 30A inlet is purposely designed to use the same mounting & hole pattern as the twist-lock standard 30A marine inlet. It will fit the old location regardless of whether the original inlet was plastic or metal. This makes installation very simple.
Smart Plug Inlet
Here we are looking at the back of the 120V SmartPlug inlet with the cover plate removed.
You can easily see that GREEN/GROUND is the bottom hole, BLACK/HOT is the right hole and NEUTRAL/WHITE is the left hole. Everything is clearly coded for a US wire color standard installation.
BLACK = 120V HOT
The SmartPlug makes installations easy. Even the clamping screws are color coded to the corresponding wire colors. This is the clamping screw for the BLACK/HOT wire.
In this photo we are looking at the side of the 30A shore power inlet.
If you are at all uncomfortable with AC wiring, and do not understand the differences between HOT, NEUTRAL and GROUND, please hire a competent marine electrician to do this install. AC wiring and wiring mistakes can kill you..!
GREEN = GROUND
All the clamping screws on the Smart Plug inlet are color coded to make it nearly fool proof. Please notice that I said nearly.
New versions of the 30A SmartPlug inlet will begin shipping with the new set screw design you will see below. There is no problem with this design but the new design makes installation even easier. These guys are constantly looking to make this product the absolute best it can be and they do listen to the trade and DIY customers, when it comes to feedback.
SILVER = 120V WHITE/NEUTRAL
The silver screw is your AC 120V WHITE/NEUTRAL wire.
I apologize for the tape residue but some of these pics were taken in 11F weather and the tape did not want to come off cleanly...
Flat Straight Blades
One of the reasons the SmartPlug can have so much more metal to metal contact surface area between the male pins and the female socket is because this is a single-action device. This means it only has to insert but does not have to twist as well. The shaping of the female socket to accept the twisting results in considerably less surface area contact.
The other reason there can be more contact area, is because the pins are flat not curved. This makes it much easier for spring tension to create a longer & wider mating area, as you'll see below.
At this point in time SmartPlugs are for the boat end only. This is the end that sees the most abuse and a 50% fix is better than no fix at all.. SmartPlug is awaiting approvals for the dock pedestal end, a long and arduous process, and once they do they will have dock pedestal products available.
Oh My, Another One
Apparently my computer has a mind of its own today and these images just keep seeping from my image database... Sorry I will try not to let it happen again..
A Very Sung Fit
The SmartPlug only inserts one way, straight in, and the male and female are unidirectional in shape thus no mistakes. When it is fully inserted it will click
so you know
it is properly installed..
I have literally seen NEMA L5-30's forced in and inserted incorrectly. This can create a very dangerous situation. This physically can not happen with the SmartPlug.
The positive locking mechanism is also a lot more robust. Because it does not involve threads, twisting and the plug can't physically wiggle once inserted, the locking mechanism actually lasts for more than a few weeks before self destructing.
A feature I really do like is the LED indicator light found on the pre-made cord sets. The field install plugs DO NOT have the LED indicator. They tried but to make them waterproof was proving too expensive on a field install plug. Factory made cord sets have a blue LED in the boat end of the cord. Nice feature... Overload the main breaker and trip it? One look in the cockpit, or at the boat end of the cord, saves you a trip to the dock pedestal.
In my experience nearly everything about the SmartPlug is extremely well thought out, and built specifically for the marine environment. This inlet is highly polished cast, not stamped, 316L stainless steel. If you break the cover off a Smart Plug inlet you're also going to have a nice hole in your boat....
The gasketing for keeping it water tight is also very well designed and engineered.
This is what it looks like inside the female SmartPlug. The receptacle is ROBUST and offers massive contact area when compared to the circa 1938 twist-lock standard.
Note how beefy the spring clamping mechanism is and the up turned guide points which make entry of the male pins seamless and easy..
This is a 50A female SmartPlug inlet not the 30A version.
These guys like to think outside the box and come up with very well designed equipment. This is their new set screw design for clamping the inlet wire.
One of the big issues with many inlet designs is the "pinching" of the wire is not always uniform or robust. You also can't drive a standard set screw directly into finely stranded wire without fracturing it. This is also against ABYC safety standards. To combat these issues the guys at SmartPlug came up with a floating & rotating head for their set screw design. This prevents fracturing the wire strands and creates incredible clamping force on the wire to create a good electrical connection.
I experimented with these set screws in my shop to see how they performed.. I clamped a 10GA UL1426 wire under one of the clamp screws 35 times. After 35 inserts and removals only two very small wire strands broke. This is pretty incredible when you consider you will only ever do it once or perhaps twice at the most.
Side View Of Set Screw Head
Here you can see the design and floating nature of the set screw head. Even under quite a bit of torque the head continued to spin in the set screw and not destroy the wire.
These Were Brand New Plugs
When I called SmartPlug, during the research phase of this article, I spend many hours or sometimes weeks researching before I delve into a detailed article, I asked about independent testing and temp scanning.
They told me that Cascade Thermal Imaging, Inc. of Redmond Washington had in fact conducted some independent, third part thermal imaging tests on the Smart Plug.
I was then able to convinced them to send me this thermal image of two brand new plugs & inlets, both 30A. One is the circa 1938 NEMA L5-30 twist-lock standard, most boaters are using today, and the other is a Smart Plug.
These plugs and inlets were both 30A versions run at 28A or 93% of the face value rating. They were loaded to 28A for 1.5 hours at an ambient room temp of 72F..
I think the image speaks for itself and represents pretty much what I see in the real world. When you look at the temp spread you can see a 23F rise in temperature, from the ambient air temp, on the circa 1938 NEMA L5-30 plug standard. Loaded identically, the SmartPlug yields just a 4F rise from ambient room temp.
I am playing devils advocate here, but there may be differences in the plug casings and how they transmit heat? My gut instinct is that I suspect 1.5 hours should be sufficient to get any heating at the plug/socket juncture to the surface of the plug.
Keep in mind that a 30A NEMA L5-30 circuit should never be loaded to this level for long durations. This was 28A in a controlled testing environment with brand new specimens. Even at this 93% of rating level the Smart Plug handles the current in a far better manner. I suspect if the NEMA L5-30 standard were tested today, to today's standards, it would have never gained approvals.
I regularly measure plug temps with my infrared thermometer, wish I had a Flir, and also see this in the real world. Here in Maine we do have a fair number of boats that winter over many of which use electric heat.
I will say it again, portable electric heaters can be VERY, VERY dangerous even on well maintained cord sets and inlets because they draw immense current. Please be CAREFUL!
The max level at which you want to load these circuits is 80%. Keep in mind this is when new
with clean & tight connections
. As the connections age corrosion can set in and this can create high resistance, especially with the 1938 twist-lock standard.
I generally don't recommend loading a NEMA L5-30 30A circuit to more than 70% of its face value rating, especially in the marine environment. This means approx 21A on a 30A circuit. If you want to push it to 80%, and feel safe about that, the number is 24A. As a marine electrician I do not feel safe about that with the 1938 NEMA L5-30 plug standard. Your boat & your choice...
Let's Be Fair
I examined rather closely the NEMA L5-30 socket and pin design and now want to show the SmartPlug 30A pin and socket. It's only fair right...?
What jumps out to me is the sheer contact area made by the SmartPlug pin and socket. Not only can the clamping spring be longer but because the pin and socket are FLAT there is a ship load more contact area.
Once plugged in and locked a SmartPlug 30A or 50A male/female socket combo CAN NOT MOVE side to side or up and down. This was a major part of the design criteria for this system..
This essentially means that no torquing or unintended loading of the spring clamping mechanism, beyond the design criteria, can occur with the SmartPlug. It does not take an engineer to see that the spring clamp can remain tighter, and in design spec for FAR LONGER, with the SmartPlug than it can with a twist-lock. It can remain in spec far longer than a twist-lock because the twist-lock allows for odd angles, twisting, unintended odd angle loading and torquing and expansion/stretching of the clamp mechanism all due to its poor design.
Sure in 1938 perhaps the twist-lock plug was the cats meow for industry and factories. Today, in 2014 we can do better and Smart Plug has done better..
Field Install Plug & Inlet
Here we are looking at the 30A field install/retrofit plug and a 30A inlet. There are FOUR points of positive locking between the inlet and the plug:
Right & left push lock connectors which are similar to the locking mechanisms found in cordless drill batteries. They are SS and lock into very thick and robust notches in the sides of the inlet.
The front portion of the lid, nearest the hinge, positively locks into the plug body.
The back portion of the lid locks positively into the plug body.
Rather than do my own video SmartPlug has already done this:
Keep It Dry
On of the biggest pit falls of the circa 1938 twist-lock design is that it is nearly impossible to gasket and keep dry. This can be an important consideration when installed just feet from a salt water environment. Corrosion is a direct contributor to high resistance. High resistance is a direct contributor to boat fires.
Due to the design this system can be very well gasketed in order to keep it as dry and corrosion free as is possible.
The Lid Also Has Gasket
Here we can see the lid gasket. When not in use this gasket keeps the pins drier..
This image also show just how thick and robust the plastic of the plug body is. This is not an accident. The robust nature of the inlet is part of the design. It needs to be robust to handle the marine environment and loads imposed by a moving boat. It also creates a nice wide gasket mating surface and a very solid area for the positive locking devices to lock into.
Holy Flaming Tamales
Darn, another one got by me...
The Grand Slam Safety Feature
So just what is this "grand slam safety feature
"? When Ken, the owner of SmartPlug, set out to design this product he wanted to incorporate a thermal breaker into the 30A inlet body to prevent melt downs due to high resistance. It was not good enough for Ken to just design a better plug & inlet, he wanted to design a truly safe product. Should be simple right?
It seems that no thermal breaker existed that could work in this type of application.
Problem number one, design and build a thermal protection system for the SmartPlug inlet.
Problem number two find a company that can make it to SmartPlug's stringent specifications and quality standards. They finally settled on a design for the thermal protection system and then found a company to manufacture it. This company is not Chinese, as one may assume, but rather a German company where labor costs are quite high.
It should be noted that the vast majority of this system is made right here in America! I like that!!
The TINNED wire used in the cord sets is made here in AMERICA!!
The thermoplastics used in the SmartPlug are all made in AMERICA!!
Assembly is all done here in AMERICA with US labor!!
The thermal breaker is made in Germany using comparable wages to US workers.
The stainless used in the SmartPlug does come from China but only out of necessity. If US Made the product would sit in US shelves because it could not be built affordable and could not be competitive. Ken tried his hardest to manufacture it all here in the US which is more than most companies will even attempt these days.
GRAND SLAM SAFETY FEATURE:
Inside the body of the 30A inlet is an epoxy potted thermal breaker that will trip at 200F. This is below the melting point of the wire jacket. Once the inlet has cooled it will automatically re-set at 110F so you don't lose bilge pumps etc..
No other shore cord system, in the world, incorporates this important safety feature. It will prevent the high resistance melt down images you have already seen so many of here.
There are some in the industry (really just one or two that I know of
) who feel an auto-resetting breaker, of any kind
, is not safe. This mind set stems from breakers re-setting into a dead short, and I agree 100% with this. However, resetting into a dead short is not the same as a high resistance thermal shut down and re-set when the junction has had time too cool down.. Your other breakers are still there, and are not auto-reset. Your other breakers will trip in the event of a dead short
. This is a thermal
REMEMBER, HIGH RESISTANCE CAN CAUSE A FIRE AND NEVER TRIP A STANDARD CIRCUIT BREAKER!
Up until now we have had no shore power thermal breakers that trip on high resistance / temperature just on overload of the circuit or an imbalance, such as an ELCI..
The argument the opponents (just possibly the manufacturers who don't care about your safety
) propose is this:
Boat owner's Darrel & his other brother Darrel get to the boat. Darrel & Darrel find no electricity. Darrel #1 opens the AC panel at the same exact moment the thermal breaker re-sets and gets zapped..
While, in theory, this could possibly happen, but this is about as likely as Rosie O'Donnell beating Lance Armstrong in a bike race. At least that owner had a chance to get onto his boat before it burned to the water line or burned the entire marina.
Like anything common sense must rule the day. We now have a safer mouse trap & a better mouse trap but it will always get hung up with second guessers & competitors
proposing supposition like I just mentioned. You will have to decide what is safer for you..
So How Do I Get A Smart Plug?
SmartPlug sales have taken off dramatically and demand is high, and for good reason. That said the product is out there and is available.
I will be honest here and say that I much prefer a new cord set and inlet as compared to the "retrofit" kit shown to the right. If your old yellow cord is in good condition then replacing the boat end is a suitable option. If however your corset is older, do yourself a favor and buy a new cord set and inlet.
Where do you buy a SmartPlug?
You can buy them right here on Sailnet but they are widely available...
Purchase SmartPlug Components (LINK)
EDIT: PLEASE be patient. This article and some others have generated a large demand and supplies may be limited. They are working to fill orders as fast as they can..