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4788 50amp connection challenge

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    #16
    You may want to do a little more research on this. I am not certain but unless they are doing something magic
    I believe these adaptor convert from a 250v50 amp plug to a 125v50amp plug, however

    I believe you will only get 25amp at the 125volt 50amp plug.

    250 volt circuits get the amp rating by adding the amperage of 2 separate 125 volt lines with opposite phase. I think the 125volt adaptor just drops one of the 125 volt lines leaving you with only 25 amps.

    The only way I am aware of to get 50 amp out of a 125 volt 50 amp plug is to start with 125v at 50 amp input

    Restating the above a little different.

    Converting from a 50 amp 250 volt plug to a 50 amp 125 volt plug is not the same as converting 250volt at 50 amp to 125 volt at 50 amp.


    Also when splitting a 250volt 50 amp circuit with an adaptor
    The input plug fits a50 amp 250volt socket and the output end is 2 - 30amp 125 volt plugs, however you only get 25amp out of each 30amp plug.


    If I am incorrect I would like to have somebody confirm I am wrong with some supporting information as I will then go buy the adaptor and always plug into a 250volt 50 amp source as that should be lower cost for power.

    4788 PH 2001, Cummins 370's
    2355 C Express, 1996 5L
    17ft Cobra, 1985, 125HP

    Exploring the Salish Sea

    Comment


      #17
      Well I did the research to my own question regarding actual amperage when pulling 120 volt from a 50 amp 240 volt circuit. I went to an RV site that had an article on the topic.

      https://www.rvtravel.com/more-power-...ur-rv-that-is/

      It turns out I was sort of right, but not quite. As I mentioined the 240 volt amperage is the sum of the amperage of each 120 volt phase, however

      Apparently a 240 volt 50 amp circuit actualy has 100 amps avaialble, each 120 volt phase provides 50 amp. That would imply that a 50 amp 240 splitter that provides 2-30 amp cord ends could actually provide 50 amps to each of the 120 volt circuit you power.

      Results of amperage out as I understand the article are as follows:

      A) When using a 240 to 120 adapter you can only use 1 phase of the power for any single120 volt circuit (if you were to combine them you get back to 240 volt) so if you have a single output 240@50 amp to a single 120@50 amp the other 120 volt circuit is not used and you only access 50 amps

      B) if you have a 240@50 amp to 2 - 120@30 amp splitter each output plug has actually got 50 amps availble. The power panel on the boat then at least for a 4788 will limit your power use by the amp ratings of the breakers for each of the 3 possible circuits that can be independantly powered, however you will have a total of 60 amps avaialble inside the boat with the spiltter Vs only 50 Amps for the single out adaptor.

      C) The only motive for using the 240@50 to 120@50 amp would be to power a single circuit that will draw more than 30 amp (up to the 50 amp available for a single phase 120volt line). In this case the 4788 uses cicuit #3 to power the electric heaters and I believe for those who have it the AC units. If all heaters on at the same time, or multiple AC units on at the same time this could exceed 30 amp. I suspect that is why some of you have a 120volt 50 amp (I presume on circuit #3). For some of us in the NW we dont have AC and circuit #3 is only 120volt@30 amp.

      The difference in the plug configurations has to do with electrical codes and assuring the wire rating sizes are adequate to handle the available amperage. Circuit #3 on a boat with a 50 amp plug should therefore have heavier gage wire, wire rated to handle 50 amp, whereas the 30 amp circuits only require a wire gage rated for 30 amps.

      I think that is how it works out, but if somebody has more knowledge on the topic I am interested in hearing it.
      4788 PH 2001, Cummins 370's
      2355 C Express, 1996 5L
      17ft Cobra, 1985, 125HP

      Exploring the Salish Sea

      Comment


        #18
        Guys. Please. The adapter is not for converting or splitting to two 30 amp circuits. I’ve described a straightforward situation and a link to the adapter I purchased. I’m reasonably competent in most things required to maintain a boat. The boat is in the PacNW and to the best of my knowledge all 4788s had two 30 amp inputs and one 50 amp input as shown on the schematic provided above. There are two paralleling switches which, reading the labels, should be connecting circuits 1 and 2 to number 3 when 50 amp is available and the switches are properly positioned.

        Somewhere along the ownership path one of the owners added reverse cycle AC post purchase. As an aside, that’s why we have an 8kw Genny and not a 12kw unit. When I noted we had power showing after connecting the cord/adapter it was only evident at the volt meter. Under no combination of switches could I get any amperage draw indicated on the ammeters and I tried turning on high draw items on each of the three breaker banks - including the AC / heater circuits. Maybe a pristine 20 year old 50 amp cord should have made me suspect some issue!

        in any case you guys have collectively provided some helpful information and enough suggestions (and missteps) to guide me thru another round of trial and error in a more structured way. If I end up with the same result then I will deinstall the Magnasine controller from its poorly chosen location, tilt the panel forward and try to determine if there was some “improvement” made along the way thru rewiring that is interfering with using the 50 amp input.

        I’ll post a follow up next week after we get settled for our trip to Chatterbox/Desolation/Octopus. Again - thanks for all the contributions!
        Patti & Gordon Lewandowski
        Sammamish WA
        1998 4788 (April 2018)
        ”Knot Home”

        Comment


          #19
          I apologize if I perhaps strayed from the original topic, I understanding that my reply does not answer your question it was a side topic that may be if interest to the far greater number of person that read these threads than those of us who contribute.

          As I understood you are converting 240 volt @ 50 amp to 120 volt at 50 amp, ( your adaptor does not supply 240 into your boat) also you indicated that all circuits worked proper on 30 amp shore power cord. If the adaptor is working correctly then it should make no difference as to the wiring inside the boat. The only points that could effect the power are

          a) The adaptor is wrong, or not working,
          B: the parallel Vs normal power selector is not functioning correctly.

          FYI, I do not have a 50 amp plug on my circuit #3, all of my plugs are 30amp from the factory. Not all of the 4788s came with your configuration.
          4788 PH 2001, Cummins 370's
          2355 C Express, 1996 5L
          17ft Cobra, 1985, 125HP

          Exploring the Salish Sea

          Comment


            #20
            From Knot Home to Knot Happy - thank you! Next step appears to be disassembly. Oh well!
            Patti & Gordon Lewandowski
            Sammamish WA
            1998 4788 (April 2018)
            ”Knot Home”

            Comment


            • Kwood
              Kwood commented
              Editing a comment
              Some folks are focusing on the adapter. It's not the adapter. The adapter is working fine and as intended. I agreed you have to examine the guts.

            #21
            Sorry we were no help.

            These 4788's had different power configurations from the factory. Yours may or may not have had the 50 ,30, 30 configuration originally, it may be an artifact of a PO having added AC. Our PNW 1999 4788 has no AC and came from the factory with three 30 amp connection and an 8kw generator.

            It makes no sense to me why your seeing voltage and nothing works. Could it be from your inverter? I have seen inverters wired very differently from boat to boat.
            Partner in a 1999 4788

            Seattle, WA

            Comment


              #22
              Star at this point I’m now really clueless. But clearly a lot of folks trying to help. Time to get back to the boat and start digging!
              Patti & Gordon Lewandowski
              Sammamish WA
              1998 4788 (April 2018)
              ”Knot Home”

              Comment


                #23
                Like other folks, I too am very curious about what/why is the culprit. I have a feeling this is a NEUTRAL line issue. The wiring diagram shows that whereas 110v/30A inlets are wired B/W/G in clockwise fashion on the connector, the 110v/50A inlet is wired B/G/W in clockwise fashion on the connector. In other words, the NEUTRAL and GROUND points are reversed. Ordinarily this should not matter since the Neutral and Ground wires should be bonded together AT THE PEDESTAL. However, if that is not the case there may be a problem there.

                Interesting puzzle.
                Retired, computer expert / executive
                Bayliner 285 Cruiser / Mercruiser QSD 4.2L 320 HP Diesel
                Live in the Bay Area, CA, USA, boat in Turkey
                D-Marin @ Turgutreis in Bodrum/Turkey
                bdervisoglu8@gmail.com
                bulent@pacbell.net

                Comment


                  #24
                  knot Home, I have been re reading your description and want to verify a few things. The power panels on these boats are absurdly complex. It actually took me 2 seasons before I fully understood all the switching. I apologize if you understand all of the following but it is complex and your description sounds like it may be operating as designed.

                  A) you indicated when you plugged in the 30 amp everything worked. I presume you powered from
                  shore-power #1 and set circuit #2 and #3 to parallel. This would Power everything in the boat on all circuits.

                  b) shore power #1 is the only circuit that can also power circuit #2 and, or circuit #3. If you plug into shore power #3 with 50 amp power and switch to normal it will only power circuit #3. When in parallel it will not power line #1 or #2 it will actually completely disconnect shore power #3, it will show you have power on line #3, however you get nothing from line three anywhere into the boat. The only benefit of using line #3 is you get 50amp to you AC and Heaters on line #3 and reduce that draw from line #1. It will not reduce the draw from line #2.

                  Power in from line #2, or line #3 will not power anything on the other two circuits. (The outlets won’t work if you only plug in line #3) if this is what you are experiencing then everything may be as it came from the factory. Simple test would be plug into line #3 and disconnect line 1, set line #3 to normal and see if your heaters or Air-conditioning come on.

                  c) No matter what you do with the system all items on circuit #1 only get 30 amps from line #1. I presume your motive was to get more power available to all appliance in the boat no configuration of the OEM shore power or parallel switching can help you get more than 30 amp to circuit #1.

                  d) Circuit #1 (at least on our panel) has 80% of everything in the boat on it. This appears to be done to accommodate the inverter. Everything on the inverter is on circuit #1. They also use line #1 for the inverter It charges the house battery once on shore power and draws up to 25 amp, the hot water tank draws up to 15 amp and the main battery charger draws up to 15 amp on circuit #1, trash compactor draws up to 10 amp This results in no matter how many shore power lines (you can plug in all three if you like). Your are still powering way more potential amperage than 30 amp limit off of line #1

                  e) The OEM circuit #2 on our boat originally only powered our range and washer-dryer. I originally thought the breaker columns under the rotary switches matched the circuit, but not so. I moved my Hot water tank and battery charger to circuit #2. Now a t least when I have 2 shore power lines the hot water tank does not draw from shore line #1. This significantly reduced the number of times circuit breaker 1 trips.

                  f) I have diagramed up another change I intend to make regarding circuit #1 and #2. I will add a parallel rotary switch similar to the ones on line #2 & #3 that will separate off several of the inverter appliance. This will allow me to run these from line #2 when available and set them back to line #1 to run from the inverter when I am operating from the house batteries.
                  4788 PH 2001, Cummins 370's
                  2355 C Express, 1996 5L
                  17ft Cobra, 1985, 125HP

                  Exploring the Salish Sea

                  Comment


                    #25
                    Actually, the wiring diagram is not so complex (at least I think I understand it).

                    There are three load networks, L3, L2 and L1 such that parallel only works between "L3 and L1" or "L2 and L1", and L3, L2 or L1 is connected to either a corresponding Inlet or the Generator.

                    I hope this helps.
                    Retired, computer expert / executive
                    Bayliner 285 Cruiser / Mercruiser QSD 4.2L 320 HP Diesel
                    Live in the Bay Area, CA, USA, boat in Turkey
                    D-Marin @ Turgutreis in Bodrum/Turkey
                    bdervisoglu8@gmail.com
                    bulent@pacbell.net

                    Comment


                      #26
                      Well KH I think you might have nailed it but it would be valuable to get feedback from anyone who has and has used the 50 amp connection. Sure seems like a waste if the 50 amp I put was limited to powering just the AC and heaters. Guess it’s also time to pull out the original manuals to see if they shed any light on this. Logic, it seems, wasn’t part of the design center.
                      Patti & Gordon Lewandowski
                      Sammamish WA
                      1998 4788 (April 2018)
                      ”Knot Home”

                      Comment


                        #27
                        May be you all are aware but here is how some pedestals are wired, using a center-tap transformer as a source.

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                        Using L1 and L2 as two separate phases, a pedestal may be wired as follows.

                        Click image for larger version

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                        The advantage in doing this is that since L1 and L2 are always exactly 180 degrees apart when voltage is rising on one, it is dropping on the other. This allows using the center tap as the return (Neutral) and using two separate phases (Line) to provide power on different outlets such that whereas the combined current from the outlets flows on the return (Neutral) line they are out of phase and the net current is only their difference!

                        The 250v 50A outlet is intended ony as a 250v input source to a boat. My guess is you are connecting that to a boat wired for 120v. In that case the 50A inlet does not have a return (neutral) line for the current to flow back. Hence you have 0 amps even though you have volts between the Line input and Neutral, which is not connected to the 250v outlet at the pedestal.

                        Please check the pedestal to make sure that the 50A outlet on the pedestal is NOT 250v.

                        This is the only explanation I can offer for your problem. Good luck.
                        Retired, computer expert / executive
                        Bayliner 285 Cruiser / Mercruiser QSD 4.2L 320 HP Diesel
                        Live in the Bay Area, CA, USA, boat in Turkey
                        D-Marin @ Turgutreis in Bodrum/Turkey
                        bdervisoglu8@gmail.com
                        bulent@pacbell.net

                        Comment


                          #28
                          Thanks MonteV. You may well be right, but then what is the purpose of a 50/250 to 50/120 adapter? Our home slip only has 30 amp power so my purchase was to take advance of 50 amp when we stay in marinas over the summer. In theory it would eliminate a lot of the power management gymnastics we go thru to keep from tripping breakers during those times we use AC at the dock. In any case, if not for boaters wanting to (successfully) connect 50/250 pedestal to a 50/125 inlet why would Marinco even offer the product.

                          Well maybe it was an artifact of the Ganges Marina. I’ll do some careful poking around the back of the panel and also try again at another transient 50/250 pedestal and see what happens.
                          Patti & Gordon Lewandowski
                          Sammamish WA
                          1998 4788 (April 2018)
                          ”Knot Home”

                          Comment


                          • Kwood
                            Kwood commented
                            Editing a comment
                            The adaptor takes one leg of the 250v and feeds it to the boat - hence 125v. The other leg is not used. You still have 50 amps capacity.

                            You have a multimeter? [If not - you need one!] Check the pedestal. Each leg and neutral. You'll see what I mean.

                            50amps feeding input #3. Parallel input 3-1, parallel input 1-2. All busses have power. See the diagram I posted.

                          #29
                          All,

                          Please understand there is a difference between voltage and current. A properly wired 250V/125V power pedestal will be capable of delivering a true 50A to a 250V load, or 50A to either or both of the two 125V "legs". Using a 250V/125V 50A to 125V converter should deliver 50A on one of the two 125V "legs". I have seen marinas that install 250V/125V connectors on the power pole that only supply 125V 50A to one of the "legs". They do this to allow boats that have only 250V/125V 50A connectors with 125V 50A power they have no ability to power 220V equipment on the boat but can supply power to all of the 125V equipment on the boat.

                          For the original poster, IF this was done and the "leg" chosen to supply the power was NOT the leg that was passed through the converter you could plug in and yet still not get 125V power to your boat. Now is this the correct way to do this, NO but you can still run into situations where this can occur.

                          When I was helping a good friend with isolating leakage issues with his 1998 vintage 47xx Bayliner the schematics showed that only the 50A line one (50A) could be correctly paralleled with the two other lines. His power panel was not wired per the schematic and I assumed a previous owner had rewired for whatever reason . These modifications were the source of his issues with leakage current.

                          Hope this helps.

                          RB Cooper

                          Comment


                            #30
                            Thanks RB. I get the difference. I simply don’t understand why, if I am showing 120v on the gauge I have no current to any of the three internal “legs” or columns of breakers. Now I thoroughly suspect some behind the panel “improvements” made before we bought the boat. Ganges was the first time since we purchased the boat that I tried connecting to 50 amp because all the marinas we had been to provided only 50/250 and we didn’t have an adapter to take the power down to one leg. As I’ve noted, time to go carefully exploring behind the panel.
                            Patti & Gordon Lewandowski
                            Sammamish WA
                            1998 4788 (April 2018)
                            ”Knot Home”

                            Comment


                            • Kwood
                              Kwood commented
                              Editing a comment
                              Where there is voltage there is current. There is current [watts / power / consumed by the voltage meter. It's only mili amps - but it's amps.

                              That's why I asked you where the voltage meter is tapped from.

                              Do you have a multi-meter?
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