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100 amp to two 50 amp dockside plug in adapter

N

northshoreone

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Oct 14, 2011
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  1. OWNER - I own a Hatteras Yacht
Hatteras Model
70' COCKPIT MY (1988 - 1997)
This past summer I was in a marina with a 74 Hatteras across the dock from me. The Captain of that boat had what appeared to be a home made splitting device(made of the appropriate marine hardware) that plugged into the 100 amp service on the dock that had two 50 amp cords coming out of it that he had the two 50 amp cords from the boat plugged into. I asked him about it and he said it was in fact home made and worked great!
My question is, has anyone here made up such a 100 amp to two 50 amp plug in's such as this? I have experienced marinas that had 100 amp service available but no 50 amp on the dock or 50 amp plug in's that either didn't work or kept tripping the breakers for no reason other than poor dock wiring or weak breakers. That being said, it would be very handy to have such a splitter on board.
I know just enough about electric to get by without killing myself so I'm looking for the electrical experts here to chime in on this! Can one of these be made up SAFELY?
 
Anything cam be made safely but to do it right you would have to put a 50 amp breaker on each leg or else you have the potential of running 100 amps through a 50 amp cord. Just because their are two 50 amp connections you are not splitting the amperage. This would be tough to do in a compact setup. To do it right you would have to go from the 100 A to a 100 A 4 position breaker with 2 50A breakers out to the two 50A connections. This would be real large and combersome exsecaly in marine grade equipment. You may be better off trying to find one pre made. I never understood a 50a to 30a reducer because you have the ability to run 50 A through a 30 A cord in that case. I don't see how that can be safe. But then again I know electrical on land more. I usually cringe when I see the electrical night mares at marinas.
 
I am not a big fan of pigtails or adapters but normally th breaker(s) on the boat side will prevent you from pulling more than the cables will handles... Ex when going from 50amp to 30amos the boat should have 30 amp breakers that will pop if you pull more than 30amps before the cables start melting :)

Personally I have never been in a situation where a marina had 100amp but didn't have two 50s as well. If you regularly go to such places, then you may want to make your own although the 100amp plugs aren't cheap :)
 
Making a splitter should not be a problem. However, the ends may cost as much or more than just buying one already made up.
 
Charles and Hubbell both have (or at least did have) what you are looking for. But I'm sure they are very expensive...especially since the situation you described is very rare. I have never experienced a need to split down to 50A at any marinas that I have stayed anywhere on the east coast. I have been at plenty of places where I needed to use an adapter from two 30A's to one 50A. If you need to do that, I would recommend the Hubbell unit with the box as part of the adapter. It is supposed to provide 50A whereas the regular pigtail just adapts a 30A receptacle to a 50A but only provides 30 A to the boat.

Walt
 
Hubbel makes them for either direction but they are very expensive. There has been discussion here before about converting two 50A to 100A on the boat side and cost was around 10K not including any labor. Those adapters retail for around 7K so the parts to make one won't be cheap.
 
The 7K adapter with the box is for combining two 50a sources into a 100a plug. This gets tricky and is not just a simple wiring job because you are dealing with separate sources and the phases need to match up. You also don't want either of the 50a plugs to have hot prongs exposed when other one is connected.

Going the other way as the OP is suggesting should cost much less. Here you are just tying two 50a cords into one source. The phase issue doesn't come into play and the plugs are safe since the two 50a plugs are female. It should be a simple wiring job that almost anyone could do if they had the plug ends.
 
SKYCHENEY said:
The 7K adapter with the box is for combining two 50a sources into a 100a plug. This gets tricky and is not just a simple wiring job because you are dealing with separate sources and the phases need to match up. You also don't want either of the 50a plugs to have hot prongs exposed when other one is connected.

Going the other way as the OP is suggesting should cost much less. Here you are just tying two 50a cords into one source. The phase issue doesn't come into play and the plugs are safe since the two 50a plugs are female. It should be a simple wiring job that almost anyone could do if they had the plug ends.
Click to expand...

Agree but the parts and the adapters are insanely expensive.
 
I see now that Wards Marine offers this set up for $2,435 .....just the parts to build the same would be close to $2K! I have purchased some portable boost transformers from them previously. They will be somewhat flexable on the price of such items. Very nice people to deal with, but for as often as it would get used, that would be a very pricey NICE TO HAVE!!
 
So these leads me to this question: why are these plug ends so damn expensive? It's not like they are super fancy or difficult to make.
 
krush said:
So these leads me to this question: why are these plug ends so damn expensive? It's not like they are super fancy or difficult to make.
Click to expand...
because they're made for multi-million dollar boats.
 
Boatsb said:
Add watertight boots too.


But will it allow one leg to power the other and will it deal with phase issues?
Click to expand...

Yes, you will want the boots for those plugs. But no you won't power any open prongs. The source is the 100a male plug. It will power both female 50a plugs. No issue there.

There is also no phase issue. You have two opposing hots in the 100a plug, one neutral and one ground. Each of those are wired to the corresponding prongs on each of the 50a plugs. No problem.

The only time you would need to worry about either issue is if you were trying to go the other way and combine two 50a sources into one 100a.
 
I was thinking 2 50 amps feeding a 100.

Hell I almost never see 100 amp power or vessels wired for it here.
 
Boatsb said:
I was thinking 2 50 amps feeding a 100.

Hell I almost never see 100 amp power or vessels wired for it here.
Click to expand...

Me either. I do see a few 100a receptacles here and there, but nobody using them and they always have 50a on the same pedestal. That's probably why the OP can't find a splitter. There just isn't much need for them.
 
I was told by another Captain that I know that in some of the Bahamas marinas the 100 amp power source was much better than the 50 amp source. Can anyone here confirm or deny that statement?
I see that Skycheney found most of the components for about $400, plus the cost of wire..boots..etc which would land it somewhere in the neighborhood of $600 which isn't so bad! I am looking at replacing one of the glendenning cords on the boat which should have plenty of good wire left to use inside the boat. My question to him would be are 50 amp breakers needed on each 50 amp leg to the boat inside what ever water tight box is used?
 
So the two 50A ends would be wired in parallel, to the four prongs on the 100A plug?
 
northshoreone said:
I was told by another Captain that I know that in some of the Bahamas marinas the 100 amp power source was much better than the 50 amp source. Can anyone here confirm or deny that statement?
I see that Skycheney found most of the components for about $400, plus the cost of wire..boots..etc which would land it somewhere in the neighborhood of $600 which isn't so bad! I am looking at replacing one of the glendenning cords on the boat which should have plenty of good wire left to use inside the boat. My question to him would be are 50 amp breakers needed on each 50 amp leg to the boat inside what ever water tight box is used?
Click to expand...
No breakers needed. The shorepower inlets on your boat are fused and each has a main breaker that would trip if overloaded.
 
Here is a very elegant way to do make this adapter for no more than about $520 and it will look very professional and work nice. I made one a few weeks ago using the same setup below.

Buy this already made up 50 amp "Y" adapter from eBay.
One 50 amp male plug input to two 50 amp female receptacle outputs.

Conntek Shore Power Y Adapter 50 Amp 125/250V To 2-50 Amp 125/250V
Item number ( 251905349491 )

One left (make an offer of $125 and I bet he takes it, Hint: that's what I paid for mine from him)


Then also buy this 100 amp marine plug from eBay.
Hubbell Shore Power Cord Connector (End / Plug) 4 Prong Male / 100AMP
Item number ( 291426278323 )

One left $319.95 (make an offer)


To make the Y cable assembly
Just cut the 50 amp "male plug" from the new Conntek Shore Power Y Adapter.
Install the 100 amp marinco male Plug in place of the removed 50 amp male plug.

The finished assembly will look store bought and also has status LED indicators. The only thing used will be the 100 amp male plug and it is only slightly used. You also only have to make up the connections on the 100 amp end. The Y splice will be factory sealed and you don't have to violate the factory make up of the 50 amp female receptacle ends.

As pointed out in previous post the input fuses on the boat will insure that no more than 50 amps will be drawn on any leg of the two 50 amp cable assemblies cable.

Tim
 
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