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Discussion Starter · #1 ·
I recently bought a 1975 Pearson 30. Shorepower was an "optional extra" at that time and was not taken up by the buyer.
When I got the boat, there was an electric heater on board and a jury-rigged power cable that was stuffed into the chain locker (photo 1). As far as I can tell, the setup was this: Plug black "custom" power cord into the dock supply with NEMA 30 A plug. Run the cord through the hawse pipe and back into the V-berth area. Then use domestic power extensions (multiple lengths) and splitters to get the power back to the saloon and galley areas (photo 2).

Photo 1: "Hacked" Shore Power System
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Photo 2: A Rats Nest of Extensions
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I brought the first parts of the "wire chain" home for further examination (photo 3)

Photo 3: The "Shore Power Cable" Plus the First Extension Cord
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Closer examination showed signs of overheating on the power strip (photo 4) and when I tried to unplug the power strip from the junction box, I could not because the plastic had melted and locked the plug in place (photo 5).

Photo 4: Overheated Power Strip
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Photo 5: Power Strip Plug Welded To the Junction Box
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There was no breaker in this system, not even a GFCI at the beginning of the cable chain (Photo 6). Finally, the cable sleeve on the extension cable had worked free from the plug (Photo 7).

Photo 6: No Protection Device At the Start Of the Cable
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Photo 7: No Strain Relief On Power Strip
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So what's going on here? Well, a properly set up shore power system will supply 30 A. There should be a breaker (on the dock) so that when the current goes a little above 30 A (due to a fault) then the breaker will trip, cutting off current. However, all of the household equipment on the boat is designed to max out at 15 A when operating correctly. With no additional protection, a fault can draw down an additional 15 A of fault current before the the dock protection equipment trips. 15A at 120 V is 1,800 W of power that often ends up generating heat. That's a whole ceramic fan heater worth of power so imaging how quickly that can start a fire.

All of the wiring here is undersized for 30 A of power. Remember the power is "I squared R" so the power goes up as the square of the current (double the current gives 4 times a much power into a given resistance or electrical load).

So what is wrong here? Starting from the dock end:
  • The 30 A plug contacts are corroded, increasing resistance and causing heating (Photo 6)
  • There is no protection device (GFCI) on the cable (remember the boat has no protection - this is a dock cable) (Photo 6)
  • House equipment used in a marine equipment (Photo 7)
  • No strain relief so pulls on the power strip pull on the wire connection in the plug (Photo 7)
  • Too much load (devices) placed on the power strip (Photos 4 and 5) Power strips are designed for domestic loads (generally less than 15 A total)
  • Extensions plugged into extensions (Photo 2 - the green cord is the FOURTH in the chain - NEVER plug an extension into an extension)
  • Inappropriate electrical fittings placed in a wet area (Photo 1)

I've complained so what would be a better solution?

Use a correctly-sized cable from the dock connection. Make sure there is a GFCI at the dock end in your cable, sized for your loads (usually 15 or 30 A). Test the GFCI each time you use it. If something goes wrong on the dock or in the boat, you will be protected by the GFCI. On the boat or dock-finger end of the cable, provide a small number of sockets using appropriate electrical fittings. Work out the power or current draw of each of the things you plan to power with the cable. Figure out how many can work together and DO NOT EXCEED THE LIMITS. Unplug a load before to add a new one. Do not leave the cable hooked up when you are not on the boat. All of this also applies if you are running temporary cables for work on the dock or outside of the boat.

Final comments:

Do not rely on the marina protection devices. Most are OK but there are many that are incorrectly wired and more that are not properly maintained. This is where your GFCI (temporary cable) or ELCI (permanently wire shore power) saves your bacon.

Bad electrical wiring kills swimmers every year. We do not have a clear picture of how bad this problem is so the USCG is undertaking a survey right now. I suspect it is a bigger problem than we know. I also suspect new regulations are on the way, including for older boats (no grandfathering).

Bad electrical wiring damages and destroys boats every year. If you don't know what you are doing, pay a competent professional - it's cheaper than replacing your boat.
 

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Mmmm. and after the fire on your boat burns your neighbors' boats down the fire marshal will want a little chat with you about your electrical wiring skills.
 

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Pearson 30
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Discussion Starter · #4 ·
Well I'm installing a "from-scratch" shore power system. Started the project but suspended when I found out the port side of the boat is very wet. We knew about one stanchion and some weeping from large fixed portlight. I have now installed new portlights together with some re-engineering and have plugged stanchion leaks. So back to the a.c. install. I'll write it up when complete.
 

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I shutter wondering how many boats around us are wired like that. Electrical is the number one cause of boat fires. By far.

It's not uncommon for me to try to visualize what I'd do, if a neighbor caught fire. Assuming I was even there. Generally involves an emergency departure, but I'm honestly not sure how realistic that is.
 

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Changed non representative title.


Thanks

Mark
 

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Discussion Starter · #8 ·
Hi MarkofSealLife. I understand it is your prerogative as admin to make changes. However this is my "creative" effort. You could have reached out and discussed. How about we meet in the middle? I'm suggesting either DON'T DO THIS (Shore Power Connection Errors) or Shore Power Connection Errors (DON'T DO THIS!!!).
 

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I shutter wondering how many boats around us are wired like that. Electrical is the number one cause of boat fires. By far.

It's not uncommon for me to try to visualize what I'd do, if a neighbor caught fire. Assuming I was even there. Generally involves an emergency departure, but I'm honestly not sure how realistic that is.
No kidding. The number of boats that run electric heaters in winter makes me crazy.
 

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As a Port Commissioner running a marina it would bug me to see "pigtails" that plugged into the dock shore power pedestal. These had the 30 amp plug then at the other end a receptacle for 15 amp plug. This means that the boat had no overload protection as the 30 amp pedestal breaker wouldn't trip when the 15 amp system was overloaded. I don't see how it's legal for these devices to be sold.
 

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Discussion Starter · #11 ·
Following Waltthesalt's comment, the correct way to do this for dockside work or temporary boat connection is: 30 A dock connector -> 30A to 15 A pigtail -> 12 AWG flexible cord with integral GFCI -> 15 A connector for plugging in tools etc. NO power strips, adapters or additional extension cords. The GFCI is sized for the application and will trip long before the dock 30 A breaker. The GFCI should be one with integral test and reset and should be checked every time the cable is rigged. This should never be left connected when the boat is unattended.
 

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it would bug me to see "pigtails" that plugged into the dock shore power pedestal.
I've never used those on a dockside pedestal and most modern pedestals I've seen have a GFCI 115v receptacle right on them. I will occasionally run an extension cord, from the pedestal, to a power tool, rather than tax the boat's wiring or branch amp capacity.

I do use reverse pigtails over the winter. Where there is a female 30amp on one end, to connect to the boat's shorepower cord, and a male 115v plug on the other, to plug the boat in on the hard, for temporary power/charging. Our battery charger actually has the ability to set the max amperage on the incoming shore cable, which I lower for this exercise.
 
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