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For those with Air Conditioning and 12KW Generator

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    For those with Air Conditioning and 12KW Generator

    My boat is similar to the 45/47/49 operating in PNW where Air Conditioning on the water is not really needed all that often. The few times I have used it I don't think I have ever run all three units.
    Equipped with 3 AC units and 12KW Genset

    While I know that to be able to run absolutely everything and no power management I need the 12KW but I find myself in a position that I might be in the market for a genset and the size of the 9kw is a bit better but the 200# savings is the compelling part.

    What is the real typical amp load on your application where the AC units are running? Spec sheets show them each at about 10A running and 17A startup. Typically when I am running genset I am doing so to make hot water and charge batteries which is about 25A and spiking up a bit more while cooking.

    If I go for 12KW it is easy but also means that it runs with minimal load on it almost all the time (~25%) where if I go down to 9KW I bump up the typical load to closer to ~33%. The slight fuel savings I might get aren't enough ongoing costs to consider.

    I should add that I am in process of adding a new inverter that has power share abilities to soften the spikes.

    Thoughts? Recommendations?

    1999 Sandpiper Pilothouse - Current
    1989 3888 - 2011-2019, 1985 Contessa - 2005-2011, 1986 21' Trophy 1998-2005
    Nobody gets out alive.

    I have 3 ac units and a 6kw genset. This setup works just fine 95% of the time. The limiting factor in my case is the 30 amp main breakers on the panel. It's easy to overload a thirty amp if both water heaters are running and we are doing laundry. what I'm getting at is the maximum power consumption for our boat is about 7.2 kw and while we have to do the occasional kabuki dance with the breakers it works just fine., we do have a propane stove though. I would think that the 9kw genset would be just fine.


      On the 45/47 all 3 AC units draw about 38 amps in total when cooling - they are 16/16/12K btu units.
      That covers the 3 AC units and the associated water pump(s) to feed the units raw water.
      When they are in reverse heat mode the amperage goes up a bit but i do not remember how high.
      Northport NY


        I'm on the south Texas gulf coast so we frequently have all three AC units running. Mine draw somewhat more than Smitty. The two 16k BTU AC units and the water pump together draw about 40 amps. The 12k AC unit draws less than 10 amps, maybe closer to 5 amps. So 45-50 amps for all three plus the pump.

        Caveat - my AC units are quite old. I think two are original. Modern AC units draw somewhat less electricity. My water pump was replaced a few years ago and it's a monster. It could probably supply a couple more AC units!
        2001 Bayliner 4788 "Fifty / Fifty II"
        League City, TX


          You should consider a Fisher Panda 15 Mini DP generator, not only is much smaller, lighter, quieter and cooler running then others in the market, it is also super reliable and easy to work on!!!....have this one on our 4588 and we can run 3 AC units in So CAl (they run no stop in the summer when we are out) and scuba compress, stove, water maker with no issues....great unit beyond happy with it!

          USCG OUPV
          1990 4588
          Carlsbad, CA


            I do not run AC but do run a very high amperage charging system at around 35 amps, plus the hot water heater, and the watermaker and even the stove all at the same time.

            I have a Northern Lights 9kw generator and love it. It is extremely quiet, and I have never been able to over load it.

            KEVIN SANDERS
            4788 LISAS WAY - SEWARD ALASKA

            Whats the weather like on our boat

            Where are we right now?


              When I had a 47 we upgraded from the 8kw to the Fischer Panda Mini 12, which is really 11kw. I GREATLY appreciated the extra capacity. Laundry, Water Maker, A/C, cooking and battery charging meant I still had to manage loads but it was much easier with 11kw than 8kw.
              1997 Pacific Mariner 65'- Permission Granted
              Detroit Diesels 8v92TTA
              NL Generators
              Novurania and Caribe RIBS, 50Merc and 60Yamaha

              Formerly 2000 Bayliner 4788
              Formerly 2001 Maxum 3300
              Formerly 1996 Celebrity 265