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Old 14-06-2012, 19:21   #1
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50 amp vs 30 amp Marina Service

What is the difference between 30 amp and 50 amp marina service? It has to be more than 20 amps!

We are currently tied up at a National Park Service marina and I am told the service is 30 amp. In order to connect I am using an adapter for my 50 amp cable. On my boat panel it "looks like" 220V service (showing two 110V "legs") but nothing on my boat that is 220V (range, washing machine etc) will operate.

I suspect the difference is that the 50 amp is 220V and the 30 amp is 110? Am I correct, or is there more to it?

BOB
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Old 14-06-2012, 19:30   #2
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Re: 50 amp vs 30 amp marina service

Actually there are 30A and 50A 110 systems and 50A 220 systems but the 50A 110 is not commonly used. Most marinas I think have 30A 110 and 50A 220.

You can look at the outlets or plugs to tell.

30A 110 has two flat blades and one blade with a corner that turns in toward the center of the plug. 50A 110 has two flat blades but the third blade has a corner that turns out.

50A 220 has one flat blade and two blades with corners that are turned out.

So how does it "look like" 220V service on your panel?
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Old 14-06-2012, 19:33   #3
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Re: 50 amp vs 30 amp marina service

Just thought of a couple of other comments.

There is no 30A 220V service that I know of.

If you think you see 110 on both legs of your 220V panel I'm guessing the adapter you are using is putting the same 110V leg on both sides of your 220V.
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Old 14-06-2012, 19:35   #4
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Re: 50 amp vs 30 amp marina service

You are essentially correct. The 50 amp circuit is two legs that are each 110v from neutral and are 180 degrees out of phase so they have 220 volts between them.

It is possible to get an adapter which plugs into two 30 amp 110v shore power circuits and gives you 220v at 30 amps (with a 50 amp plug)--but they are expensive.
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Old 14-06-2012, 19:48   #5
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Re: 50 amp vs 30 amp marina service

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Originally Posted by donradcliffe View Post
It is possible to get an adapter which plugs into two 30 amp 110v shore power circuits and gives you 220v at 30 amps (with a 50 amp plug)--but they are expensive.
Are you describing an adapter that would invert the phase of one 30A outlet to give you 220V against another plug from the same 110V circuit?

If not you are just getting 2 30A 110V circuits connected together unless you can find two 30amp plugs that are already out of phase.
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Old 14-06-2012, 20:08   #6
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Re: 50 amp vs 30 amp marina service

FYI

It is more than the Ground blade turning in or out. Blade width and position is critical. Most 50 amp have a center guide pin on the female for voltages 125v-480v

Hope this helps

http://www.hubbellcatalog.com/wiring.../section-b.pdf

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Old 14-06-2012, 20:12   #7
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Re: 50 amp vs 30 amp marina service

Look at the female end of the plug. The part that goes into your boat. Does it say 50A 125/250 or 50A 125?
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Old 14-06-2012, 20:39   #8
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Re: 50 amp vs 30 amp marina service

To add just a bit more, most marinas are fed by a three phase system of 120 volts on each hot leg, a neutral, and a safety ground. The 50 amp dock outllet boxes are staggered using two of the 3 hot phases, and a neutra/safety ground. The two hot phases in a 3 phase system are electrically 120 degrees out of phase on the 50 amp service, so the two 120 volt phases only add up to 208 volts instead of 240 volts. Between the Hot and neutral, it will still be 120 volts. If you look at a West Marine catalog, it shows the 50 amp plugs rated for 250 volts. It's sort of confusing, but it makes sense because you may go to some old marina or the Islands where the 50 amp feed is a single phase system that will give you 240/250 volts between two 120/125 volt hot phases 180 degrees out of phase.. Check your panel meter to see what is shows.
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Old 14-06-2012, 22:32   #9
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Re: 50 amp vs 30 amp marina service

Quote:
Originally Posted by Caribsailors View Post
FYI

It is more than the Ground blade turning in or out. Blade width and position is critical. Most 50 amp have a center guide pin on the female for voltages 125v-480v
Certainly there is more to it than the angle of the blade. Yes the blades are different sizes, spacing, etc. but for a non electrician the descriptions would provide the OP a simple way to visually identify the three most common marine connectors used in the US.

Not sure if I understand correctly what you're describing but in a marine context I have not seen any 50A plugs with what I would call a center pin. Three blades or three holes and on the 50A 240v a ground plate on the side.
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Old 15-06-2012, 08:53   #10
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Re: 50 amp vs 30 amp Marina Service

First, thanks for all the replies.
My conclusion is that the service here is 30 amps at 110V
I am using an adapter to connect my 50A/220V cable to the hook up.
The hookup allows 2 flat pins and one with a bend towards the center.

It "looks like" I have 220V on my panel, because my panel shows two active "110V legs" just like it does when we have 50A/220V service. But apparently that is not a correct interpretation.

The bottom line is that I will fire up a generator later today so my wife can do the washing. Either way, the frig is running and the beer is cold.

Thanks to all, BOB
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Old 15-06-2012, 09:03   #11
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Re: 50 amp vs 30 amp Marina Service

Quote:
Originally Posted by rblackman View Post
First, thanks for all the replies.
My conclusion is that the service here is 30 amps at 110V
I am using an adapter to connect my 50A/220V cable to the hook up.
The hookup allows 2 flat pins and one with a bend towards the center.

It "looks like" I have 220V on my panel, because my panel shows two active "110V legs" just like it does when we have 50A/220V service. But apparently that is not a correct interpretation.

The bottom line is that I will fire up a generator later today so my wife can do the washing. Either way, the frig is running and the beer is cold.

Thanks to all, BOB
Sounds like the dock is definitely 110V and probably 30 A although there is a 110V 20 A plug that superficially looks the same as the 30A plug but I haven't seen one of these in many years.
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Old 15-06-2012, 09:13   #12
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Re: 50 amp vs 30 amp Marina Service

Bob, when in doubt about what voltage an outlet is providing, stick a voltmeter in it. And when in doubt about adapters and outputs...I'd suggest not using them unless you are SURE of what the result will be. Sometimes, if the voltage is not matched, you'll wind up with a fire, and that can ruin the day. From high voltage OR from low voltage, as devices try to work with the "wrong" one, either way.

Like Edison said about Tesla, that AC electricity, it'll just sneak out of the sockets and kill ya at night. <weg>
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Old 15-06-2012, 09:17   #13
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Re: 50 amp vs 30 amp marina service

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Originally Posted by donradcliffe View Post
You are essentially correct. The 50 amp circuit is two legs that are each 110v from neutral and are 180 degrees out of phase so they have 220 volts between them.

It is possible to get an adapter which plugs into two 30 amp 110v shore power circuits and gives you 220v at 30 amps (with a 50 amp plug)--but they are expensive.
Was intrigued by this concept so did a little research. All the adapters I found specified you had to plug the two 30A 110V plugs on the Y adapter into dockside outlets with the 110V hot legs 180 out of phase . So if you're a dock with only 30A 110V I would bet all the hot legs would be from the same circuit so you would only get 110V.
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Old 15-06-2012, 09:34   #14
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Re: 50 amp vs 30 amp Marina Service

We started cruising almost two years ago and now have a bag full of adapters... Our boat has two 30a/125v and one 50a/125v shore power connections. Yes, I know, but Catalina thought that was best...

Anyway, in our non-scientificsurvey we have found that most new marinas carry 50a/250v & 30a/125v shorepower connectors. Some even carry 50a/125v, but not very often. The older marinas typically have one or two 30a/125v shorepower plugs. Finally, some of the real old marinas have 20a/125v plugs.

The adapter used most by us is the Marinco Y-Pigtail. It has a 50a/250v male plug and two female 30a plugs.. It basically takes the 250v dock power and makes two 30a/125 plugs. hen we power mange our boat.

Marinco has a pigtail for every occasion and West Marine Advisor is helpful.. here is a link:

The West Advisor: Shore Power
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Old 15-06-2012, 11:18   #15
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Re: 50 amp vs 30 amp Marina Service

So much for cruising being any less environment destructive than living in a condo ;-)))

BTW 50A is OK - you can always elect to use less than that!

Hugs,
b.
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