30 amp source with 50 amp system

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Johnny

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Dec 12, 2012
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Currently Chartering
I am chartering a boat with a 50 amp electrical system. It has a "Y" adapter with the power cord so when visiting a marina with only 30 amp service you can connect to two 30 amp receptacles. My question is, if there is only one 30 amp receptacle available can I connect one leg of the "Y" adapter to the 30 amp receptacle and be careful how much equipment I run? Do you think I could run reverse cycle heat and a few cabin lights? Is it dangerous to leave one leg of the "Y" adapter open?

Thanks
 
I have the same 50 amp 250 volt cord and intelligent combiner box for my boat. My understanding (I could be wrong) is that the electronics that are in the box are supposed to make sure you are plugged into 2 30 amp services of different phases so that a 220 volt AC or water heater will work. Believe box is supposed to disconnect if you lost one leg or they were on the same phase.

Ted
 
Assuming it's a proper adapter cable supplied with the boat, it's what's more correctly called a "Reverse Y" because it combines two 30A 120V circuits into one 50A 120/240V. A "splitter" would split a 50A 120/240V circuit into two 30A 120V circuits. The connectors will be different (opposite sex), and the operation is different in a subtle, but important way.

Now, to answer your question.... No, it won't work. A proper Reverse Y detects the presence of the two 30A 120V circuits, ensures they are out of phase so they correctly combine to create 240V, and only cut through the power if everything checks out. It's an important safety feature.

I say "proper" reverse Y because there are plenty of people who hack together something that will work under certain circumstances if you really know what you are doing (most people don't) and are really careful, but it's just too dangerous in the hands of most people. But I would be really surprised if a charter boat were supplied with such a hack job.
 
Thanks!

How about if there is a single cord adapter that mates the 50 amp cord to a 30 amp receptacle, think I can run reverse cycle heat and a few cabin lights?
 
I think that what has been said before is mostly correct, but I am a bit surprised that one 120V, 30 amp leg won't partially work. No you won't be able to use any 240V appliances on the boat but it is rare to have any.

But it should be possible for the connected 120V leg to supply power to its respective 120V breaker buss on the main panel. There will be two such busses and only one of them will be powered if only one leg is connected.

So give it a try. I don't see anything that makes it unsafe to run off of one leg if the reverse y splitter will let it.

David
 
Johnny said:
How about if there is a single cord adapter that mates the 50 amp cord to a 30 amp receptacle, think I can run reverse cycle heat and a few cabin lights?
Click to expand...

Most likely "no" on the heat since on a 50A boat it is most likely 240V. Lights, maybe, but now you are asking to go down the hackery path and create something dangerous. If you are asking these questions, then you are exactly the person who shouldn't be playing with it. Just use two 30A outlets and the supplied adapter like it's supposed to have.
 
djmarchand said:
I think that what has been said before is mostly correct, but I am a bit surprised that one 120V, 30 amp leg won't partially work. No you won't be able to use any 240V appliances on the boat but it is rare to have any.

But it should be possible for the connected 120V leg to supply power to its respective 120V breaker buss on the main panel. There will be two such busses and only one of them will be powered if only one leg is connected.

So give it a try. I don't see anything that makes it unsafe to run off of one leg if the reverse y splitter will let it.

David
Click to expand...


Dave, where it becomes dangerous is if any 240V appliance has been left on, creating a path for the powered leg to feed back to the un-powered leg. Yes, you can go make sure they are all turned off, but what if someone mistakenly switches on the hot water heater?

You are correct that it CAN be done, but in my humble opinion it SHOULD NOT be done by anyone who doesn't really know what they are doing, and someone asking how to do it is just such a person.
 
Looks like the Hubble smart "y" will not let you use only one leg...I could be wrong but here is a snapshot from their catalog

"Features and Benefits
3 pole contactor breaks both hots and neutrals to prevent possibility of “live” plug when not engaged.​
​

You may need a 30 to 50 single adapter....the other doesn't sound right but I can't find anything to the contrary yet.

​
 
Gosh sorry I asked Twisted...

How do you learn if you don't ask?
 
Or better yet run the genny. We had to run the genny multiple times in the Bahamas do to unreliable power.
 
djmarchand said:
I think that what has been said before is mostly correct, but I am a bit surprised that one 120V, 30 amp leg won't partially work. No you won't be able to use any 240V appliances on the boat but it is rare to have any.

But it should be possible for the connected 120V leg to supply power to its respective 120V breaker buss on the main panel. There will be two such busses and only one of them will be powered if only one leg is connected.

So give it a try. I don't see anything that makes it unsafe to run off of one leg if the reverse y splitter will let it.

David
Click to expand...

I would tend to agree...as not all boats with 50 amp 125/2450V are wired for 240V...

But I think that's why they are called smart "Y"s cause they may not work (see my previous post) on only one leg to prevent any backfeeding.

If you did have only 2 separate 110 panels and no 240...then I have to ask someone better in electrical than me...could you just wire up a "dumb" "Y" ? or is something going on with the neutral that I don't know about that may be dangerous? (yes you would have to cap the unused 30 prongs even though they wouldn't be hot unless you had an internal problem in the boat.)
 
Johnny said:
I am chartering a boat with a 50 amp electrical system. It has a "Y" adapter with the power cord so when visiting a marina with only 30 amp service you can connect to two 30 amp receptacles. My question is, if there is only one 30 amp receptacle available can I connect one leg of the "Y" adapter to the 30 amp receptacle .......... ?
Click to expand...
I'm going to go out on a limb here and suggest that you ask the person or company that is providing the boat.

Regardless, you can only get 30 amps from a 30 amp receptacle so you're not going to be able to run some appliances.
 
I have a Mainship 36. I have two 30A cords to a 50A "Y" which is normal.
Inside my boat on my power board with all the circuit breakers, I have a 3 position switch at the top. Line 1 - Line 1&2 - Gen
Pos. Line 1 is for when you only have one 30A receptacle. It will run the entire boat on that one line which is also the forward plug outlet outside the boat.
Pos Line 1&2 is when I have either the 50A "Y" with the 2 30A cords going to it or 2 separate 30A receptacles on the doc.
Pos. Gen is when I use either the Gen or my Inverter.

There is no magic inside the "Y" adapter. It is simply wired so that the 50A 220V AC plug wiring is broken down to two 30A 120V AC circuits inside the cord.

If you have only one 30 A circuit avail on the dock, your boat is limited to 30A total
by both the dock 30A circuit and your boats 30A Circuit breaker. Also on my boat, my Ckt Breaker Panel is broken down into 2 separate panels. Like I said earlier, if I use the Line 1 position with only one cord (my forward one), both panels will have elcctricity but limited to 30A total.
I hope this isn't too confusing.
 
If it is a 50amp panel than no it will not work on that splitter. You need a 30-50A adapter and than only the 110V side will work. We have both for our 50A boat.
 
With 50A 220V you have two hot leads and one neutral.
With 30A service you have 110V - 0ne hot, one neutral and 1 ground.
If you think you know what you are doing you can make it work on 110V but wont have a ground wire. Not good. So you really don't know what you are doing.
If you really, really don't know what you are doing you will have 110V where your ground should be and it wont be a pretty ending.
 
Tony B said:
With 50A 220V you have two hot leads and one neutral.
With 30A service you have 110V - 0ne hot, one neutral and 1 ground.
If you think you know what you are doing you can make it work on 110V but wont have a ground wire. Not good. So you really don't know what you are doing.
If you really, really don't know what you are doing you will have 110V where your ground should be and it wont be a pretty ending.
Click to expand...

Most marinas are 50A 125/250V 4 wire...red, black, white, green..and so is a 50A 125/250V power cord. The green is the ground like normal so I'm not quite sure where everyone is going with this.

The interior panel is what varies with some boats taking advantage of the 250V and some just using the increased power to have 2-50 amp 125V busses. Thus the advantage over 2-30 amp panels (busses).

The OP's question about using a smart Y cord adapter is a good one...I didn't know if they would allow hooking up only one leg and still have it work...from the quick read in the catalog...no the smart Ys need both legs hooked up and a single 30-50 adapter is needed. I'm guessing that a 30-50 amp splitter (to a 125/250V 50 amp cord) only powers on leg (panel).
 
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I've got a 50-amp outlet at my berth. Since my boat's systems use 30 amps, I need to use an adapter. Most every time at other marinas, the power is 30 amps. Seen many boats with dual cords, but I'm ignorant of their workings.

img_210891_0_a561b52fb194b5cfe307c01cab206fc6.jpg
 
My older 1986 model is low tech
All I could contribute is what I have.
Never know if they have the same set-up or not.
 
The simply wired no brain Y will be happy to function .

As it will only light off 1/2 the boats 120, you will have to select which 120 circuit has the fridge and other goodies , the other circuit may mostly be for added air cond.

Beware as each 120 leg is expecting 50A , not just 30A the adapter/power pole can provide.

The CB on the dock post will let you when you get too power thirsty.

Folks that cruise have 2 choices for low power pole areas.

1. is a following inverter that can boost the amperage during high use times , and recharge the batt set at low consumption times , about $4,000

2. install load shedding relays , about $60. each EG so the HW heater will be shut off when the reefer turns on.

With a handful installed living on 120V 15A can still be a fine lifestyle , but no air cond.
 
psneeld said:
The OP's question about using a smart Y cord adapter is a good one...I didn't know if they would allow hooking up only one leg and still have it work...from the quick read in the catalog...no the smart Ys need both legs hooked up and a single 30-50 adapter is needed. I'm guessing that a 30-50 amp splitter (to a 125/250V 50 amp cord) only powers on leg (panel).
Click to expand...

Your guess is correct. They won't work unless both ends are correctly connected. That's where the "smart" part comes from. It's a safety precaution to prevent inadvertently creating an energized, exposed 30A plug when you have just the other 30A side plugged in. And it also verifies that the two 30A outlets you are supposed to be plugged into are indeed out of phase so you have 120/240V on the 50A end.
 
Both Marinco and Hubble marine power cords have one available. They are so you can use a 50 Amp power panel on a boat that requires 2 separate and out of phase 110V legs to make 220V. The smart part is just some solid state circuitry with switching that tests to see if you are hooked up correctly so you don't create a dangerous situation.

Wow... that sounds so simple I hope I'm not insulting you but even I'm not sure of all what the cords "actually" do or don't as the literate on the web is thin.

http://www.marinco.com/files/media/product/catelogs/Marinco%20pg27.pdf

http://ecatalog.hubbell-wiring.com/...ubbell-wiring.com/press/catalog/y.pdf&Page=26
 
psneeld said:
Both Marinco and Hubble marine power cords have one available. They are so you can use a 50 Amp power panel on a boat that requires 2 separate and out of phase 110V legs to make 220V. The smart part is just some solid state circuitry with switching that tests to see if you are hooked up correctly so you don't create a dangerous situation.

Wow... that sounds so simple I hope I'm not insulting you but even I'm not sure of all what the cords "actually" do or don't as the literate on the web is thin.

http://www.marinco.com/files/media/product/catelogs/Marinco pg27.pdf

http://ecatalog.hubbell-wiring.com/...ubbell-wiring.com/press/catalog/y.pdf&Page=26
Click to expand...

You are correct.

Simply, with an intelligent combiner, if both 30 amp male plugs aren't connected to out of phase outlets, you get no power out of the 50 amp 250 volt female plug, period!

Ted
 
twistedtree said:
Most likely "no" on the heat since on a 50A boat it is most likely 240V. Lights, maybe, but now you are asking to go down the hackery path and create something dangerous. If you are asking these questions, then you are exactly the person who shouldn't be playing with it. Just use two 30A outlets and the supplied adapter like it's supposed to have.
Click to expand...


We can supply some power to our 50A/240V boat with a single 30-to-50 amp converter.

I don't know what power distribution is like inside the boat if we use the converter. The AC panel is divided into two sides (two legs), so I would guess the single 30-to-50 amp source may power only one side or the other. I know it does power the side with our charger (converter), since that's the only thing I've tried this way, once when wintering on the hard.

(None of our appliances (AC, etc.) are 220V; everything is 110V. We have two ACs and two fridges, one on each side of the panel.)

In fact, we ran that charger from a 15A power source, converted to a 30-amp connector, converted to a 50-amp connector.

I understand some of the newer boats in our line have an isolater installed, so a single 30-amp input will not work the way it does with ours.

FWIW, we've had limited success with the Marinco "Smart Y" -- but the couple three times we've wanted to use it, we could usually pin down the problem to either phasing (30A supplies weren't opposite phases) or voltage (supply couldn't achieve the advertised minimum of 208V).

-Chris
 
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So, this smart part with the solid state circuitry is inside the cord itself?
I can run my boat entirely off one 30A cord ( as long as I don't go over 30A) or two 30A cords to a 50A "Y".
My boat has worked with and without the smart cords.
How did my model year 1986 work without the smart cords?
 
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Johnny said:
I am chartering a boat with a 50 amp electrical system. It has a "Y" adapter with the power cord so when visiting a marina with only 30 amp service you can connect to two 30 amp receptacles. My question is, if there is only one 30 amp receptacle available can I connect one leg of the "Y" adapter to the 30 amp receptacle and be careful how much equipment I run? Do you think I could run reverse cycle heat and a few cabin lights? Is it dangerous to leave one leg of the "Y" adapter open?

Thanks
Click to expand...

I'm gald i did not ask this question a year ago.
Many of these responses are making assumptions.
I may be making an assumption, bit let's take the question as asked.
If no 50 A outlet, he plugs his 30 A cord into the outlet without using the adapter. Wasn't that the question?

Then, on the boat, on one of his circuit panels, the circuits shold be separated (MY ASSUMPTION), if so, he diecides what circuit to power (based on what he wants to use) IF NOT, THEN READ ALL THE ABOVE BC IDHAFC.:nonono:
 
There are enough permutations and combinations of shore power and panels that it makes it difficult to discuss them all on this forum. One of the best things a captain can do is to make a single line diagram of his boats electrical system. When I first got my boat I noted a parallel/ tie switch next to my ship shore switch that completely baffled me. Here are a couple of things I learned after making my single line diagram.

My shore power comes in on 2-30 amp 125 volt cords. They are typically out of phase but do not need to be because I have no 220 volt users.

the two shore powers are separate and stay separate in my load center. Basically one cord feeds my HVACs and the other all the rest of my loads.

If there is only one 30 amp shore power available it feeds the whole boat if I switch the parallel/tied switch to tied. Tied disconnects the second shore power and links all the AC breakers in the load center together.

It is also interesting that my generator is set up to provide 110volts. When switched to ship the generator provides power to all the 110 volt circuit breakers and the tied/parallel switch does not come into play.

My electrical set up is very ingenious but I would never have understood it had I not created a single line drawing of it. I was deathly afraid of that tied parallel switch until I understood its purpose.
 
obthomas said:
There are enough permutations and combinations of shore power and panels that it makes it difficult to discuss them all on this forum. One of the best things a captain can do is to make a single line diagram of his boats electrical system. When I first got my boat I noted a parallel/ tie switch next to my ship shore switch that completely baffled me. Here are a couple of things I learned after making my single line diagram.

My shore power comes in on 2-30 amp 125 volt cords. They are typically out of phase but do not need to be because I have no 220 volt users.

the two shore powers are separate and stay separate in my load center. Basically one cord feeds my HVACs and the other all the rest of my loads.

If there is only one 30 amp shore power available it feeds the whole boat if I switch the parallel/tied switch to tied. Tied disconnects the second shore power and links all the AC breakers in the load center together.

It is also interesting that my generator is set up to provide 110volts. When switched to ship the generator provides power to all the 110 volt circuit breakers and the tied/parallel switch does not come into play.

My electrical set up is very ingenious but I would never have understood it had I not created a single line drawing of it. I was deathly afraid of that tied parallel switch until I understood its purpose.
Click to expand...

Well said, but mine is even simpler, as I have no parallel switch. Each cord goes to a 30 amp circuit and everything on my panel is labeled.I decide which circuit to use if I can use only one. The two A/Cs are on different circuits.
 
Tony B said:
So, this smart part with the solid state circuitry is inside the cord itself?
I can run my boat entirely off one 30A cord ( as long as I don't go over 30A) or two 30A cords to a 50A "Y".
My boat has worked with and without the smart cords.
How did my model year 1986 work without the smart cords?
Click to expand...

There's usually never a problem going from a 50 amp 125/250V source slpit to 2-30A cords...it's the other way around where you have to worry about the different phases and back-feeding the one 30amp leg with exposed prongs.
 
OMG I think I'll just cancel my charter! Just kidding...

Thanks for all the info though! What I think I have learned is the smart Y cord that is on the boat, (two 30 amp legs join into a box with indicator lights on it) will not allow me to connect to a single 30 amp service for safety reasons. I think I may be a able to use a 30 to 50 amp adapter but will only power some of the equipment. I can always run the generator but may not be popular in the marina....
 
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