A Smart Plug Kit
In today's day and age it is far and few between that I come across products that:
#1 Do as they say.
#2 Are built to an exceptional standard.
#3 Redefine what GREAT is.
The SmartPlug 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 DESPISE THIS ANTIQUATED & ARGUABLY 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 standard to continue in the marine environment.
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 marginally adequate plug & socket combination for marine shore power cord/plug/receptacle use. This twist-lock standard would likely never gain approvals under today's electrical safety standards.
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, 20X 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 & USCG data)are the result of this antiquated and unsafe twist-lock standard we currently use.
Of those 55% of boat fires nearly 54% of that number is caused by "shore power". That means that nearly 25% of all boat fires start in the shore cord/power system. Wow!!!!!
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 vesselís 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 boatís Inlet Receptacle, the device on the boatís 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 antiquated 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.
Here is a prime example of where your support comes in handy. I paid for this socket out of my own pocket. Support for this site through DONATIONS (LINK)
help keep this site FREE and the in-depth brutally straight forward articles coming your way. Do your part and help support this site !!!
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..
Many have said to me that the problem is not the design, but rather how boat owners improperly use these cords and don't use the locking rings. Do you see any locking rings on this dock pedestal? Why is there no locking ring at the dock end?
While many boats owners do improperly uses these cord sets, and this can lead to high resistance, many of them still fail and burn up even when being properly used with the locking rings properly used and installed.
Many of these locking rings fail within a few months use or just fall off and disappear entirely. Others simply cross thread them and ruin them. Should the ring falling off or cross threading even be possible if this is so critical to the performance of the cord set?
It is a combination of a poor design that is not well suited to the application and sometimes no option to use the cord-set properly even if an owner wanted to.
I Cut The Plug Open And Exposed The Actual Sockets
My goal here was to show exactly why or how this standard can result 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
If you click this image you will be able to see the locking dimple on the female socket that locks into the hole on the pins of the male plug. Why is this important? Read on...
Socket Riding On Spot Dimple For Contact Area
Please do yourself a favor and blow this image up. 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 go over some of the major issues with this standard that lead to safety issues.
#1 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.
#2 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.
#3 We are trying to use this on boats and boats MOVE!!!
#4 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.
#5 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.
#6 The socket clamping mechanism/spring clamping feature is made from material just 1mm thick.. It does not take much pressure to loosen a 1mm spring clamp and provide less pressure for good contact.
#7 There are no thermal breakers in these plugs or sockets to open the circuit in the event of over heating, due to high resistance. Instead this can lead to a fire or darn near..