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Old 09-17-2021, 01:43 PM   #1
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Default Using 30amp to 50 amp Y cable??

My marina only has 30amp outlets and my boat I'm closing on has a Y adaptor that I think goes from two 30s to the 50amp. My marina says that wont work unless they had two separate bus runs. The marina is poorly wired and the dock is probably on the same AC bus.

I only really care about battery charging on dock... so can I use a 30amp fed through a splitter into my 50amp and get any power?
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Old 09-17-2021, 02:11 PM   #2
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Not sure what model boat you have. How my 3300 works, there are 2 circuits that you can plug on their own wire runs to the dock, or you can use one plug and use the panel switches to run both circuits in parallel or power one side of the panel or the other. With a Y cable you can power both circuits but the system senses that it is parallel wiring and illuminates the parallel light on the panel. Power the side with the battery charger on it if that's all you need ... that won't draw anything close to 30 amps. On anything other than 2 wire runs to the dock you need to be selective with what you run simultaneously. I've run a Y cable off of a 30 amp outlet and used the panel to select my loads. It's been fine simultaneously running the battery charger, AC, 110v receptacles (for things like phone chargers and an LED TV), the refrigerator, and ice maker. I'd imagine if I added the stove and water heater it would flip the breaker on the dock post, but I don't use those other than to test them for operation at the start and end of the season. When I do that I flip everything off at the panel except for the item I'm testing.
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Old 09-17-2021, 02:16 PM   #3
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Its a 2001 4600

The whole "220v" thing is throwing me off.

Does the AC/Heat units run on 220, but everything else is 120?

Can I use a simple 30a to 50amp pigtail to run my battery charger, hot water, etc which would only need 120v.

I've been reading through a trawler forum which is helpful.
https://www.trawlerforum.com/forums/...oat-36412.html
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Old 09-17-2021, 02:23 PM   #4
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ah you've got a big boy ... mine is all 110v, sorry I can't be of more help
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Old 09-20-2021, 12:44 AM   #5
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I have a 41SCA which has a single 50A input. All appliances, circuits, etc. on the boat are 120V including the two 16000 BTU AC's, Micro and stove. If you have a "smart splitter" like I do, then it takes two different phases of dock side 30 A power to activate it (safety reasons) and allow current to flow into the boat's panel.

If you have a 30A to 50A "pigtail", you should be able to run power to one side of your panel or both sides. Depends on how the pigtail is configured on the 50A plug. If it only feeds one 120 circuit, find out which one the battery charger is on and wire the pigtail to supply that side.

Today, 50A dockside Power connections are fed by different phases to help balance the current draw/demand.
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Old 09-20-2021, 01:29 AM   #6
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I have a bit of a smaller marina that doesn't have 50amp anywhere. I also believe that the the "box" I'm at are all on the same phase. The marina contracts a "30amp" hookup, but doesn't say you GET 30 amps.

If my whole dock is on the same phase, I'm thinking a smart splitter wont work and maybe a pigtail will? All I really need is power to the basic system.

I wont have ownership of the boat for another week so I can't test. The area the boat is currently slipped are all 50amp breakers, so I can't test until I move her to my marina.
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Old 09-20-2021, 03:56 PM   #7
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Yes....if the dock power at the new marina is all the same phase, then the commercially available two 30 - to single 50- will not work. This is for safety reasons. These are commonly referred to as "smart splitters".

When I refer to a "pigtail", I'm referring to a single 30 to single 50 that you purchase (Marinco, see pics) or you construct for yourself. I bought mine from West Marine. The 30 amp HOT is jumped together on the 50 A HOT side. So your 30 amps are available to both sides of your breaker panel in the boat.
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Old 09-20-2021, 11:10 PM   #8
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Quote:
Originally Posted by Glenn111 View Post
The 30 amp HOT is jumped together on the 50 A HOT side. So your 30 amps are available to both sides of your breaker panel in the boat.
THIS is what I needed to hear!! Thank you!
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