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Old 01-09-2018, 09:32 AM   #1
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Power from 30a outlet to 50a boat?

What's the best way to provide 110v 30a source to a 50a boat, to run the 110v stuff? Like the charger. I occasionally run into a situation where 110v 30a is the only choice, like at home where it's docked.
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Old 01-09-2018, 10:04 AM   #2
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The best way is to buy an adapter from a marine retailer (Marinco, Hubbel, etc.). The second best way is to make one but you have to be sure of what you're doing and it won't be waterproof.
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Old 01-09-2018, 10:09 AM   #3
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The best way is to buy an adapter from a marine retailer (Marinco, Hubbel, etc.). The second best way is to make one but you have to be sure of what you're doing and it won't be waterproof.
ABoatman,

Thx, do you have a model number, or what it would be called? Would it plug into the shore end of my cord?

Thx
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Old 01-09-2018, 10:37 AM   #4
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ABoatman,

Thx, do you have a model number, or what it would be called? Would it plug into the shore end of my cord?

Thx
It would plug into the end of your shorepower cord.

I think this is what you want but you would be better off going to the store to make sure:

https://www.westmarine.com/buy/marin...81?recordNum=2

This seems way more expensive than it needs to be so they may have a cheaper adapter in another brand. You're looking for something with a male 30 amp plug and a female 50 amp receptacle. You would plug your 50 amp cord into one end and plug the other end into the 30 amp shorepower pedestal.
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Old 01-09-2018, 11:14 AM   #5
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What's the best way to provide 110v 30a source to a 50a boat, to run the 110v stuff? Like the charger. I occasionally run into a situation where 110v 30a is the only choice, like at home where it's docked.

We can do that with a Marinco 30-to-50 amp pigtail (adapter), similar to what aboatman posted but not the EEL version and I remember ours being WAY WAY WAY less expensive, likely from West Marine.

I've also read that it won't work for 50A/250V boats with a galvanic isolator --
which we don't (yet?) have. In that case, I think a Smart Y and two out-of-phase 30A supplies would be required.

-Chris
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Old 01-09-2018, 11:19 AM   #6
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Not all 30 to 50s are (were) created equal....unless now they are.

When I was looking for mine a few years back, Furion was the only one I could find that split the dock 30 to both 50 legs on the boat.

Plus Furion was generally cheaper.... and has worked flawlessly the last 3 years being used quite often.

Works fine with a galvanic isolator and not sure why it wouldnt.
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Old 01-09-2018, 11:19 AM   #7
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Originally Posted by aboatman View Post
It would plug into the end of your shorepower cord.

I think this is what you want but you would be better off going to the store to make sure:

https://www.westmarine.com/buy/marin...81?recordNum=2

This seems way more expensive than it needs to be so they may have a cheaper adapter in another brand. You're looking for something with a male 30 amp plug and a female 50 amp receptacle. You would plug your 50 amp cord into one end and plug the other end into the 30 amp shorepower pedestal.
Thx, I've seen these, expensive and poor reviews. There has to be something out there that works.....
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Old 01-09-2018, 11:49 AM   #8
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Thx, I've seen these, expensive and poor reviews. There has to be something out there that works.....
But did you read the reviews? Most were sort of stupid.

Go to West Marine and tell them what you need and see what they have. most of the folks at WM are pretty sharp and if they don't know they will ask. And even though WM is often more expensive than mail order, if it doesn't work for you, they will take it back and refund your money. No shipping, no hassle.

A galvanic isolator should make no difference. It's in the ground circuit, not the current carrying conductors.
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Old 01-09-2018, 11:56 AM   #9
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Good points, will call West, they do have good customer service.
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Old 01-09-2018, 12:02 PM   #10
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I have a 50 amp service. An adapter, 50 amp female to 30 amp female, plugged into the boat makes it into a 30 amp service. Then a 30 amp shore power cord eliminates the need to muscle around the much heavier 50 amp cord. I have been able to run both a/c units at the same time plugged in to 30 amps.
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Old 01-09-2018, 12:43 PM   #11
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Works fine with a galvanic isolator and not sure why it wouldnt.

I haven't really got a clue about that.

It came up relative to questions about how to charge batteries while on the hard. I allowed as how all I had to do was plug in a single 30-to-50 pigtail, connect that to the boat power, done. (Actually, I was even starting with a household 15A circuit out in the yard's back lot; had to use an adapter from that to 30A first.)

Some of the other owners said that didn't work for them because they had galvanic isolators (starting the year after ours was built). Something about needing two legs for any of their chargers to work at all. Unless maybe they happened to have 240V chargers? Ha. I hadn't thought of that.... Bet that might have been it.

Edit: another "Ha!" It was "isolation transformer" that they mentioned, not a galvanic isolator. If that makes any difference...

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Old 01-09-2018, 01:46 PM   #12
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We use a 30 amp power cord plugged into a 30 amp shore power outlet and a Marinco adapter between the cord and the 50 amp boat inlet. Everything on the boat works except the reverse cycle heat/AC because it is 250 volt. We use the 30 amp cord because it is easier to handle than the 50 amp cord.
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Old 01-09-2018, 02:01 PM   #13
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Me too. Don't need the 50A setup except to run air conditioning, which doesn't seem to be an issue very often on the Inside Passage.
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Old 01-09-2018, 03:57 PM   #14
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I haven't really got a clue about that.

It came up relative to questions about how to charge batteries while on the hard. I allowed as how all I had to do was plug in a single 30-to-50 pigtail, connect that to the boat power, done. (Actually, I was even starting with a household 15A circuit out in the yard's back lot; had to use an adapter from that to 30A first.)

Some of the other owners said that didn't work for them because they had galvanic isolators (starting the year after ours was built). Something about needing two legs for any of their chargers to work at all. Unless maybe they happened to have 240V chargers? Ha. I hadn't thought of that.... Bet that might have been it.

Edit: another "Ha!" It was "isolation transformer" that they mentioned, not a galvanic isolator. If that makes any difference...

-Chris
If you have an isolation transformer on your boat (a heavy and expensive device but nice to have) you don't need a galvanic isolator. That could prohibit using a 30 amp to 50 amp adapter.
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Old 01-09-2018, 03:59 PM   #15
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I have a 50 amp service. An adapter, 50 amp female to 30 amp female, plugged into the boat makes it into a 30 amp service. Then a 30 amp shore power cord eliminates the need to muscle around the much heavier 50 amp cord. I have been able to run both a/c units at the same time plugged in to 30 amps.
If your adapter is female to female, how do you connect the 30 amp cord which is female on the boat end?
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Old 01-09-2018, 07:59 PM   #16
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I blew it (brain f... ?) ,the adapter is 50 amp female to 30 amp male.
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Old 01-10-2018, 06:22 AM   #17
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There are usually 2 types of adaptors:
Smart Y will connect 2 'out of phase' 30A dock receptacles to a single 50A female to plug your 50A cord into-these are expensive ($3-500)but will allow you to run 240v appliances, AC etc ('though you will only get 30A total so need to manage your power draw). You must have 2 active 30A sources one providing L1, the other L2, or the "smart" Y won't work.
Second type is a simple 30A male- 50A female pigtail (typically<$100). it routes the ground to the outer collar for the 50A and connects the hot wire from the 30A to both L1 & L2 legs of the 50A receptacle. This will not power 240v appliances but may run 110v circuits depending on how your boat was wired.
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Old 01-10-2018, 07:23 AM   #18
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Most boats with 50-240 have little use for real 240, they just need 2 120V legs.

This requires a jumper to connect both 120v legs to the single 120v leg from a 30a outlet.

This is best done (tho expensive ) with a short purpose built unit., at the power pole using marine components .

IF a 30 A light weight power hose is used the 240 plug will simply have the red and black wires connected.

This works fine ,,,until you forget the vessel is only getting 30A and you turn on too much load.

The 30A plug will loose a terminal in its black wire., or you could melt the 30A wire.

If the boat only needs the ability for a home dock , using RV electrical parts is safe and 1/5 the cost , but not suitable to breaking salt water waves.
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Old 01-10-2018, 07:23 AM   #19
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If you have an isolation transformer on your boat (a heavy and expensive device but nice to have) you don't need a galvanic isolator. That could prohibit using a 30 amp to 50 amp adapter.

Yeah, I don't have either, hence my basic lack of understanding how they work, or symptoms when/if something doesn't work...

And we have no 240V appliances either, so the simple 30-to-50A adapter works fine for light loads.

I've asked the other owners for a memory refresher, so maybe the guys who told me about it in the first place can help me clarify whatever the heck it was I was trying to remember...

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Old 01-10-2018, 08:13 AM   #20
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I blew it (brain f... ?) ,the adapter is 50 amp female to 30 amp male.
Yes, that would work with a 30 amp power cord. The adapter can be on either end of the power cord but if the OP only has a 50 amp cord (because he has a 50 amp boat), he can either buy an adapter for the shore end or buy what you describe and a 30 amp cord.

That said, a 30 amp cord is far less expensive than a 50 amp cord and if he's going to leave it out in the weather for years to come, the 30 amp cord might be the way to go.
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