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Old 08-10-2010, 12:18   #1
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Adding Shorepower Amperage Capacity

Our 40' trawler has the typical 30 amp 120v AC shorepower system. Unlike 20 years ago when you were lucky to find 30a of shorepower, our slip is equipped with 50 amp service. We are in Seattle and winters are cold and wet. At the dock, I like using our electric heaters but 30 amps can get over-committed pretty easily when even modest levels of resistance heat are turned on.

I have been wondering what would be needed to add 20a of capacity without the cost of replacing our 30a panel? Is it acceptable to add a 3 or 4 breaker 20a or maybe even a 30a panel in parallel? Would we need to add a new panel with a single 50a breaker and tap off of that to serve the existing 30a and a new 20a panel? What would we do about the shorepower plug-ins beside upgrading the cable to 50a?

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Old 08-10-2010, 12:28   #2
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Why not split your extra winter heating load off the main panel and run it on its own breaker

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Old 08-10-2010, 13:30   #3
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My trawler was rigged simular I have gen set wired with 2 seprate circuts and the shore power the same 2 amp circuts
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Old 08-10-2010, 13:48   #4
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Two thirty amp circuits give you a lot of power and flexibility. Use a 50 amp Marinco splitter to split the 50 amp service into two 30 amp.

You will need to install a new shorepower inlet, hopefully right beside the existing one. Then add a 3 breaker panel somewhere next to your existing one. Use a 30 amp breaker as the main one and then wire that one to the second and third. Wire the shore power inlet to the new panel with 10 guage wire.

Now install a 15 or 20 amp breaker in the 2,3 position and wire it to a dedicated convenience outlet for your second electric heater.

Oh and if you want to meet ABYC standard, then install another 30 amp breaker near the new inlet.

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