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    30A service questions-gctid569632

    I'll start this by stating the obvious, I'm not an electrician.

    How does the 30A shorepower cord that plugs into my boat compare to my house current of 110V? Yeah, I know I'm comparing two different units of electrical measurements.

    I see 30A and 50A service at some marinas, yet both convert to what I would call house current when the boat is plugged in.

    I'm confused :unsure:

    Thanks.
    Bob
    "Easy Living"
    2007 Discovery 246, 5.0L MPI, CC, B3
    Boating on the Rappahannock River, Virginia

    #2
    I am not an electrician either, but here goes.

    Your shore power and house receptacles are both 110v. Your house will just have usually at least 100 amp service. Your house will be able to able to run more things at the same time.

    For instance a 1500 watt 110v electric heater will draw 12.5 amps from the source(shore power cable, house breaker box), so if you have two heaters turned on in your boat, (25amps) you are almost at the capacity of what the plugs,cable and breakers can handle.

    In your house two heaters would only be a quarter of what everything can handle.

    I am sure an electrician on here can explain it a little better. B)
    Joel
    1987 3818 Hino 175
    "Knotty Girl"
    Prince Rupert B.C.

    Comment


      #3
      Voltage and current are two different things. Voltage MUST always be matched, period! Your home has 120v outlets in most places, except the stove and dryer, which are 240v (if they are electric). There are other things that might be 240 but those are the big ones.

      Current (amps) can be mismatched, as long as the supply side is greater than the load being put on it. So you could plug your boat into a 120v, 5 million amp outlet and be fine.

      Marinas normally come in four flavors:

      120v 15a or 20a with a standard household plug (uncommon)

      120v 30a with an L5-30R twist-lock receptacle ready for the most common boat cable, L5-30P.

      120v 50a with an L5-50R twist-lock (used on larger boats)

      240v 50a with an L6-50R twist-lock (used on huge boats)

      Most of the time you will find the second one, and the 50a service is next most common. If you see this often, get yourself an adapter that has an L5-50R on one end and L5-30R on the other. That will mate with the L5-30P on your standard boat cord.

      DO NOT plug into a 240v service!

      Comment


        #4
        Oh, and all these connectors are supposed to prevent crossing between the wrong ones, but some can be forced to fit. They should fit perfectly and without effort. Don't force it if it's not a good fit, check to see what your connectors are. All twist-lock connectors are marked with their NEMA number as well as the volts/amps.

        Comment


          #5
          Pretty much the same concept...

          Both are 110V single phase service. Residential receptacle circuit is usually 15/20 amp circuit so #14/12 wired.

          30amp 3prong (1 hot/1 neutral/ 1 ground) is just bigger so wired in #10 shore power cable..,
          Joon, Kathy, Jaden & Tristan
          Uniflite 42 AC, DD 671N
          93 3058 sold
          92 2855 (day boat)
          91 Fourwinns 205 (lake boat)
          Longbranch WA
          Life is Good

          Comment


            #6
            While on the topic.. So why does my boat split into 2 connectors on the boat side, never quite understood the logic for that.
            BLOG ABOUT MY BOAT... www.seattleboater.com
            5788 Man 610's- Love Her !
            Sold:Bayliner 3587 | Extended Hull

            Comment


              #7
              It's the same as US house electricity. The only difference is the total amperage that can flow through. If you have 30A service then you total usage is 30A. Microwave, refrigerator and AC may max that out-- just add up the amps. Most house now are 200A. So throw in tv's ovens stoves dryer washer. You get the point.

              Mainiac

              Comment


                #8
                "SwampNut" post=569652 wrote:
                Voltage and current are two different things. Voltage MUST always be matched, period! Your home has 120v outlets in most places, except the stove and dryer, which are 240v (if they are electric). There are other things that might be 240 but those are the big ones.

                Current (amps) can be mismatched, as long as the supply side is greater than the load being put on it. So you could plug your boat into a 120v, 5 million amp outlet and be fine.

                Marinas normally come in four flavors:

                120v 15a or 20a with a standard household plug (uncommon)

                120v 30a with an L5-30R twist-lock receptacle ready for the most common boat cable, L5-30P.

                120v 50a with an L5-50R twist-lock (used on larger boats)

                240v 50a with an L6-50R twist-lock (used on huge boats)

                Most of the time you will find the second one, and the 50a service is next most common. If you see this often, get yourself an adapter that has an L5-50R on one end and L5-30R on the other. That will mate with the L5-30P on your standard boat cord.

                DO NOT plug into a 240v service!
                Not sure your right on this one Carlos,

                There are two different plug ins for 50amp

                There is 50 amp125

                Or a 50amp 125/250

                I have the latter which is 125/250, which can be 240v, but my boat s a twin 50 amp 120 service, it is split in the adapter
                www.boatyardgm.com
                www.pacificyachtimports.net
                2002 Carver Voyager 57
                "Making Waves"
                3988 250 Hinos
                "The Dark Side"
                Alameda, California

                Comment


                  #9
                  Nobody knows.

                  It's magic.
                  Midnight Star
                  1996 3587
                  Twin diesels, Hino 250's
                  Ladysmith, BC
                  History: 1996 - 2655, 2001 - 2855, 1984 - 3270

                  Comment


                    #10
                    "simbad" post=569675 wrote:
                    While on the topic.. So why does my boat split into 2 connectors on the boat side, never quite understood the logic for that.
                    ****************

                    I think that you are talking about the boat having 2- S/P inlet fittings.

                    If so, these would likely be 2 - 120 vac 30amp inlets.

                    The reason is that the boat's total AC demands are greater than what a single 30 amp S/P supply will offer.

                    So.... the boat builder, or fitter, separated the main panels into two, giving each one it's own S/P inlet.

                    You'll need to experiment to learn which panel services which loads.
                    Rick E. Gresham, Oregon
                    2850 Bounty Sedan Flybridge model
                    Twin 280 HP 5.7's w/ Closed Cooling
                    Volvo Penta DuoProp Drives
                    Kohler 4 CZ Gen Set

                    Comment


                      #11
                      If you think it of like a water pipe, volts (120v) are like the pressure and amperes (amps) are the diameter of the pipe. If you have the wrong pressure (hook your 12v car stereo to 120v house current) you will fry it, but plug your 5 amp toaster into your 30 amp boat service, or your 200 amp home service and it will draw the same 5 amps. Something like your garden hose connected to the 6" water main in your street. Your home 200 amp service has the potential to do more "work" then your 30 amp boat service.

                      Most marina and boat fires are caused by faulty electrical service. Take the condition of your electrical service as seriously as you do your oil changes and strainer cleaning - the electrical neglect can kill.

                      Comment


                        #12
                        While on the topic.. So why does my boat split into 2 connectors on the boat side, never quite understood the logic for that.
                        If you turn on every single thing on the boat and max out the receptacles circuit, you will be drawing more than the 30a that a single connector can handle. So most cruisers include two inputs. Most also include a transfer switch so you only have to hook up one. If it doesn't, then you need a splitter if you prefer to run a single cord.

                        I have the latter which is 125/250, which can be 240v, but my boat s a twin 50 amp 120 service, it is split in the adapter
                        The plugs are rated for that, but the actual voltage provided is 120/240. As far as splitting the 240, does your connector have four prongs? I haven't seen that before, but I definitely am not around huge boats all that often where those would be used. Does your cord use a NEMA SS-2 connector?

                        Comment


                          #13
                          "SwampNut" post=569883 wrote:
                          While on the topic.. So why does my boat split into 2 connectors on the boat side, never quite understood the logic for that.
                          If you turn on every single thing on the boat and max out the receptacles circuit, you will be drawing more than the 30a that a single connector can handle. So most cruisers include two inputs. Most also include a transfer switch so you only have to hook up one. If it doesn't, then you need a splitter if you prefer to run a single cord.

                          I have the latter which is 125/250, which can be 240v, but my boat s a twin 50 amp 120 service, it is split in the adapter
                          The plugs are rated for that, but the actual voltage provided is 120/240. As far as splitting the 240, does your connector have four prongs? I haven't seen that before, but I definitely am not around huge boats all that often where those would be used. Does your cord use a NEMA SS-2 connector?
                          My Tiara's main shore power cord was a single cable 240VAC/50A on a Glendinning reel. Since so many marinas and yacht clubs don't have 240V, Tiara supplied an adapter that had 2 - 30A L5-30r male plugs that fed into a single L6-50R. Occasionally I found power pedestals that weren't wired correctly. If they took both the 110V blacks off the same leg, you couldn't get 240.

                          That boat spoiled me; it also had a single 110V 30A inlet, and the panel automatically switched between the 110 and 240 supplies, or even reversed the polarity if the dock power wasn't correct.

                          Comment


                            #14
                            There's a difference between US 240V service and regular 240V service. In the US 240V is "generated" by two 120V lines with opposite phase (sine and cosine) whereas the regular 240V is a single sine against Neutral. For this reason you can split the US 240V service into two 120V lines if the Neutral is available (that's why Carlos asked for the 4-prong plug). If you hook up a US wired 240V system to a regular neutral based 240V and rely on the splitting you will be in for a big surprise.... (240V fried equipment on one circuit and nothing on the other.....)

                            Comment


                              #15
                              Lots of good info here in regards to the OP's question. Most boats will have only 110VAC connections, generally 30A. or 50A. As they get bigger, the connections may be split, so that the boat has 2 30A. or 50A. connectors. This is because the total amperage draw would exceed a single 30A. or 50A. input if everything were turned on. If you look at your AC breaker panel you will see it normally split into two sets of breakers if you have dual inputs. One side will be fed by one input connector, and the the other side fed by the other input connector. It is important to note that if you have two 30A. connectors, this would require TWO 30A. sources so as to not overload the source, IF you were to use all your equipment at once. What normally occurs is that a splitter gets used, and ONE 30A. source will feed BOTH inputs. IF YOU DO NOT MONITOR YOUR LOADS, THIS SET-UP WILL LEAD TO OVERLOADING THE SOURCE ON THE DOCK IF YOU SHOULD POWER TOO MUCH EQUIPMENT AT ONCE. Normally, this would just trip the breaker at the dock power box, but should the breaker be faulty it could cause an overload, which usually results in a fire eventually. Also note that even with a 50A. source feeding a dual 30A. input, you can overload the source. It is vital to always monitor your AC loads while hooked to shore power.

                              The split source, 125/250VAC (or 120/240), is generally provided through a 4-prong connector. It resembles the power that comes into your house, in that 250 (240) VAC is available between the two hot leads, with a neutral between that will provide 125 (120) VAC between it and either of the hot leads. The fourth prong is ground. It is important when using this type of connection to try and balance the loads as much as possible between the two hot leads and the neutral when connected for 120VAC. If this is rated as a 50A service, it should be able to provide 50A. for each leg, or 50A. between legs (240AC). Again, you do not want to put 50A on one leg and nothing on the other if you can avoid it, because it will unbalance the line and you will be popping breakers on the loaded line all the time.

                              I like the plumbing analogy. Volts=pressure, Amps=flow. Volts x Amps=Watts, or how much work gets done.

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