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  1. #11

    Re: 240 volt from two 125’s using a splitter

    Quote Originally Posted by Sea Horse View Post
    Plugging into two 30 amp 125 V power will not give you more than 208 volts just like plugging into the 50 amp dock outlet may give 50 amp service but still only 208 volts. I have no idea why they make and sell this device and feel like I was taken since it clearly says on the splitter that it will take two 125 v lines and boost it to 240 v with 30 amp service but higher voltage.
    Just a mathematical observation: 125 + 125 = 250. So 240 would not be a "boost."

    You're misreading what the product says. All it can do is combine two opposing phases of 125V. It's not a booster or transformer. It's only capable of doing what already exists in a 250V 50A power supply. It's made for situations where a marina doesn't have 50A service, but you can find two opposing 30A services and combine them. The device also prevents you from pushing 60A (30+30=60) through 50 amp wiring and starting a fire.

    Your marina's problem is that it's using two phases from 3 phase power which are not perfectly opposed, whereas single phase 250 has two legs that are perfectly opposed so you get full voltage when you combine them.

    P.S. Don't ask how three legs of power is three phase and two legs is single phase. I find it very frustrating too.
    --- The poster formerly known as Scrod ---

    I want to live in Theory, everything works there.

    1970 36C375

  2. #12

    Re: 240 volt from two 125’s using a splitter

    208 is normal between 3 phase power legs and common in commercial installations. If there using single phase (less common and more expensive to build out) you would get 240 between the 2 legs.

    Most hatts in that size have a transformer in the system. It can be rewired to do what you need if it's there. Look again or call hatteras to see if it was or was not installed.
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  3. #13

    Re: 240 volt from two 125’s using a splitter

    Interesting that you have two gensets on that boat. Or did you trade up to a larger Hatteras yacht?

    If you have run into this problem before, maybe the boosting transformer isn't such a bad idea. Easy for me to spend your money, of course, but if it has been a frequent problem, it might be worth a second look.

  4. #14

    Re: 240 volt from two 125’s using a splitter

    Before spending the money for a boost transformer (which I did), be sure you have an isolation transformer
    on your boat and have a competent marine electrician set it up with a switch so you switch between
    208V and 240V. Right now it's obviously set at 208, as was mine but from what I have learned on this
    forum, it's not too difficult to switch to 240v by moving some wires to different poles. I think a selector
    switch is absolutely necessary however as you may stop at a marina with the 240v availability and if
    your transformer is rigged wrong you will actually get much more than 240v and plenty of trouble$$$.
    I remember some years ago someone posted the instructions for rigging your isolation tranformer to
    allow switching between 208 and 240. It may have been Sky...

    Walt

  5. #15

    Re: 240 volt from two 125’s using a splitter

    Quote Originally Posted by Boatsb View Post
    208 is normal between 3 phase power legs and common in commercial installations. If there using single phase (less common and more expensive to build out) you would get 240 between the 2 legs.

    Most hatts in that size have a transformer in the system. It can be rewired to do what you need if it's there. Look again or call hatteras to see if it was or was not installed.
    Just to clarify and back up what Scott is saying and help dispel a myth everyone needs to know that you just don't add the two low legs together and that will be your single phase voltage between. It seems that simple but its not. It depends on the utilities transformer supplying the power. You can have 2 120 VAC circuits with only 208 between them. You can also have 2 110/115 VAC circuits with 240 between them. Mine is almost 250 at my house.

    And sorry Sea Horse, it was a waste of $ because all that splitter is good for is taking when only 2 30 amp plugs are available and bringing it in as single phase 208/230/240 into the boat. It is at least as good for that if needed.

    Another twist just so all can understand it is what the utility is suppling is out on Long Island NY there is what is called a "hot leg". They bring in 3 phases. 2 are 120VAC to neutral. 3rd is 208 to neutral. Not sure but I believe they also bring in 2 hot legs with 1 120 and other 208 to neutral.

    CLEAR AS MUD! Other issues are long undersized cables and junctions to account for voltage loss.

  6. #16

    Re: 240 volt from two 125’s using a splitter

    Quote Originally Posted by Oldlaxer1 View Post
    Sky, can you elaborate? We only get 208 at our dock and I'd like to boost it.
    This thread explains how to add a boost switch to your transformer:

    https://www.samsmarine.com/forums/sh...ST+TRANSFORMER
    Sky Cheney
    1985 53EDMY, Hull #CN759, "Rebecca"
    ELYC on White Lake--Montague, MI

  7. #17

    Re: 240 volt from two 125’s using a splitter

    To clarify:

    1) Boats without transformers do not have a problem with 208v service on anything that is run off of a single pole breaker. That is because the voltage from any one leg of 3 phase 208 to neutral gives you 120v. That same boat will only have 208v on double breaker loads that would normally run on 240v.

    2) Since the isolation transformer "makes it own" power and does not use the neutral from shore, it will only produce half of the input voltage on the same single pole loads. So, you get 104v when plugged into 208v service. This is what most people notice.

    3) If you wire a boost switch to the transformer, you switch to different length windings on the transformer so that the input and output voltage is not the same. On our transformers, you can boost the output by about 15%. So, the 208v in becomes 240v out or 120v on each leg.

    4) When you do use the boost, you also lower your total amperage available by 15%. So a 50 amp service will only provide 43 amps. But that is what you always get when you use a 208v input no matter if you boost or not.
    Sky Cheney
    1985 53EDMY, Hull #CN759, "Rebecca"
    ELYC on White Lake--Montague, MI

  8. #18

    Re: 240 volt from two 125’s using a splitter

    Sky is also correct because only X Watts are available based on line voltage and amps. Doesn’t matter how you use it after it leaves the source (shore connection). I will admit with all my experience that it’s still confusing on how the amp load available works on single phase between two hots and then 3 phase. Know how to do it for energy calcs but not clear on how it works for overcurrent. Lots of good knowledge here so that helps a lot.

    There is a reason why when someone has a weird electrical issue many just respond with call an expert because that is what is needed. Do this stuff every day with BMS and sub metering but I am still an amateur. That means I know just enough to be dangerous.

  9. #19

    Re: 240 volt from two 125’s using a splitter

    I'm not an electrician and don't claim to be an expert on this issue. But, I have wired several of these boats with boost switches and they work well. All of them had the same transformers wired the same way. And everyone has been very happy with the results.
    Sky Cheney
    1985 53EDMY, Hull #CN759, "Rebecca"
    ELYC on White Lake--Montague, MI

  10. Re: 240 volt from two 125’s using a splitter

    What marina are you at in Montauk? I usually stay at Star Island and have no problems with 50a. It may be worth switching where you stay.

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