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Old 29-01-2015, 12:00   #1
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Home Made Shorepower Cords

Another thing I have noticed walking here on the dock is that nearly all the sailboats here are from the UK and they employ home made shore power cords. This includes not only 30 amp cords, but the 50 amp 125/250 cords as well.
It appears that the boat owners have bought the Marinco male and female connectors, and attached them to a piece of outdoor extension cord. Sometimes, on the 30 amp cords, the boat end of the cord retains the female plug that came with the extension cord.
I know that a 30 amp cord runs about $100 and the 50 amp ones are almost $500 for a 50-foot cord. Expensive, yes. But when you consider that the 50 amp Marinco etc. cord is make up of four 6 gauge wires plus insulation, and compare to the size of these home-made lines, seems to me that there is a fire waiting to happen.
Just compare the size of the cords in these photos, home-made versus the standard
Most of these yachts by the way look like they are worth well over $1 million.
Makes me wonder about what other short cuts lurk inside. Or am I wrong?
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Old 29-01-2015, 12:35   #2
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Re: Home Made Shorepower Cords

Where is here? West Indies? In Europe (Italy) I was always taken aback by how thin the cords were and how often they had non factory installed ends. I got used to the fact that the cords were thinner because they were running 220 volts. As far as the ends -- there are a few different types of ends that Marina's use there so perhaps it isn't practical for a store to carry the factory ends for all the different marina. I'd be interested to know what an electrician thought about self installed ends. I don't see a big problem with them if they fit correctly though I guess they are not as water tight.
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Old 29-01-2015, 18:47   #3
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Re: Home Made Shorepower Cords

Here is West Indies.
Understood that higher voltage permits one to use thinner cables for the same wattage, because the amps are lower. But if you are using a 125/250 volt connector and getting 250 volts and 50 amps, you are pulling through up to 12,500 watts--twice as much if you were pulling through 125VAC
So I cannot see why a thinner gauge wire would be as safe.
What I have read is that in Europe the amp are 16 for smaller power cords at 220v and 32 amps at 220v for the larger cords. Further, that the European shore power cords for the latter are not safe for 50 amps.
Still seems to me that the 12 gauge wire is undersized for 12,500 watts
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Old 29-01-2015, 18:53   #4
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Re: Home Made Shorepower Cords

I… er… a friend I know went to Cuba once where upon checking in at Marina Hemingway, the electrician promptly cut the male end off the cord and hardwired it into the pedestal…. thereafter, a “homemade” cord is all that was on that boat!
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Old 29-01-2015, 19:13   #5
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Re: Home Made Shorepower Cords

I just clicked on a wire size calculator Wire Size Calculator and found that 208v three phase can run 50 amps on a #10 wire if you drop it to single phase it would require a #8. I don't understand why but I guess the number of phases is the big difference.
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Old 30-01-2015, 06:51   #6
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Re: Home Made Shorepower Cords

Lots of people think it's OK to "cheap out" on electrical equipment because they don't really understand it. I am qualified to make my own shorepower cord but once I pay for the proper and safe materials, it's about the same price as a factory made cord and the factory made cord is waterproof because the ends are molded.
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Old 30-01-2015, 07:02   #7
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Re: Home Made Shorepower Cords

Quote:
Originally Posted by dohenyboy View Post
Here is West Indies.
Understood that higher voltage permits one to use thinner cables for the same wattage, because the amps are lower. But if you are using a 125/250 volt connector and getting 250 volts and 50 amps, you are pulling through up to 12,500 watts--twice as much if you were pulling through 125VAC
So I cannot see why a thinner gauge wire would be as safe.
What I have read is that in Europe the amp are 16 for smaller power cords at 220v and 32 amps at 220v for the larger cords. Further, that the European shore power cords for the latter are not safe for 50 amps.
Still seems to me that the 12 gauge wire is undersized for 12,500 watts
Small cords keep the snow on the docks melted.
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Old 30-01-2015, 07:08   #8
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Re: Home Made Shorepower Cords

So you're saying you saw </= 30 amp cords plugged into 50 amp circuits?

I guess the right answer is that this is a fire waiting to happen. The wrong answer is that it all depends on what's plugged in at the other end, and assuming that the owner is scrupulously careful about that, it's not a problem.
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Old 30-01-2015, 07:30   #9
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Re: Home Made Shorepower Cords

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So you're saying you saw </= 30 amp cords plugged into 50 amp circuits?

I guess the right answer is that this is a fire waiting to happen. The wrong answer is that it all depends on what's plugged in at the other end, and assuming that the owner is scrupulously careful about that, it's not a problem.
It's a bad idea to assume anything. As long as there is an open receptacle on the boat, someone might plug something into it. A coffee pot here, a hair drier there, an electric space heater .....................

I feel a little insecure when I'm forced to use a 50 amp to 30 amp adapter at a marina because I have a 30 amp boat and power cable. Sure if I try to draw more than 30 amps my boat's master breaker will trip but there's nothing protecting the cable itself from overcurrent (up to 50 amps). Well, at least the fire will be outside of the boat. Or in the ten feet inside the boat between the shore power inlet and the panel.

Realistically, it's hard to imagine a way for a problem to happen that wouldn't trip the 50 amp dock breaker.
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Old 30-01-2015, 08:06   #10
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Re: Home Made Shorepower Cords

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...and found that 208v three phase can run 50 amps on a #10 wire if you drop it to single phase it would require a #8. I don't understand why but I guess the number of phases is the big difference.
Three phase provides triple the power (using one extra wire) over the equivalent single phase distribution. This is assuming a balanced three phase load though. If you are tapping a single leg of three phase you still need to engineer it appropriately.
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Old 30-01-2015, 10:02   #11
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Re: Home Made Shorepower Cords

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It's a bad idea to assume anything. As long as there is an open receptacle on the boat, someone might plug something into it. A coffee pot here, a hair drier there, an electric space heater .....................
Well true enough, but anyone who runs space heaters on their boat is not going to plug them into the boat's 110. They're going to run them to a 30/50 amp adapter plug at the power pylon on the dock and I don't know a soul who uses a 30 amp cord for that. Technically it's A Bad Idea but pretty much everyone does it with a cord rated for the load.
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Old 30-01-2015, 10:10   #12
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Re: Home Made Shorepower Cords

Ends of SP cords often burn and fail. Some of those you see may be SP cords with an end replaced. It's all about wire size and a good connection.
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Old 30-01-2015, 10:21   #13
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Re: Home Made Shorepower Cords

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Originally Posted by rwidman View Post
It's a bad idea to assume anything. As long as there is an open receptacle on the boat, someone might plug something into it. A coffee pot here, a hair drier there, an electric space heater .....................

I feel a little insecure when I'm forced to use a 50 amp to 30 amp adapter at a marina because I have a 30 amp boat and power cable. Sure if I try to draw more than 30 amps my boat's master breaker will trip but there's nothing protecting the cable itself from overcurrent (up to 50 amps). Well, at least the fire will be outside of the boat. Or in the ten feet inside the boat between the shore power inlet and the panel.

Realistically, it's hard to imagine a way for a problem to happen that wouldn't trip the 50 amp dock breaker.
Ron, could you explain a bit more? We have 200A servcie at our house. I rarely use all 200A of that service. That doesn't mean I have a problem, does it?

My understanding of NEC is that my boat is considered "an appliance" as far as shorepower is concerned, and I have my "own" breaker(s) on the boat.
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Old 30-01-2015, 10:56   #14
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Re: Home Made Shorepower Cords

Quote:
Originally Posted by rwidman View Post
I feel a little insecure when I'm forced to use a 50 amp to 30 amp adapter at a marina because I have a 30 amp boat and power cable. Sure if I try to draw more than 30 amps my boat's master breaker will trip but there's nothing protecting the cable itself from overcurrent (up to 50 amps).
About the only fix for that is to have a 30 A breaker or fuse in the 50 to 30 adaptor.

Quote:
Realistically, it's hard to imagine a way for a problem to happen that wouldn't trip the 50 amp dock breaker.
Any conceivable situation where the current is over 30 A and less than the 50A breaker's actual trip point is the risk zone. Granted, the most likely fault is a short somewhere on the 30A cable, and the 50A breaker would trip on that before the cable overheated.

The point of proper protection is so you don't have to accept risks because you decide that they're not very likely.

Just saying. I've occasionally taken calculated risks too, but it's not something that should be assumed to be safe practice. You don't want every punter using a 50 to 30 adaptor and a 30A cord without understanding what the risk is.
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Old 30-01-2015, 11:19   #15
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Re: Home Made Shorepower Cords

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Originally Posted by Suijin View Post
Well true enough, but anyone who runs space heaters on their boat is not going to plug them into the boat's 110. They're going to run them to a 30/50 amp adapter plug at the power pylon on the dock and I don't know a soul who uses a 30 amp cord for that. Technically it's A Bad Idea but pretty much everyone does it with a cord rated for the load.
???????

If there's a 120 volt socket, it's an invitation to plug a 120 volt appliance into it. There's an electric space heater on my boat right now, plugged in because my reverse cycle AC failed and the replacement hasn't been delivered yet. It's a 30 amp wired boat.


What's different between me and some people is, the heater is designed so it cannot possibly tip over, it's sitting on top of the stove and arranged so it can't fall off and it's on the 600 watt setting.

So - your assumption is not valid. And you now know someone who plugs a space heater into a 120 volt receptacle. And why.
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