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Old 21-06-2017, 19:02   #1
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Join Date: Mar 2008
Location: Akron, Ohio
Boat: Bristol 29(1967)
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Isolated 120 Volt 30 Amp Service

My needs are few ... microwave(1000 watts), toaster, coffee maker and heater(1500 watts).

The OP was using 2-line electric to 2 outlets and to a plugged in charger to charge an isolated battery to run a Frigoboat fridge. I was told this wiring would suffice since it's an isolated system.

The wiring for 30 amp(from the electrical box), evidently requires 10 guage or larger wire ... it has 14 guage. No fuse, no breaker no where on the AC side .... just the hot and the common ... not good.

I'm going to put in a 30 to 15 amp breaker box(3 separate 15(or 10?), amp lines, plus ground fault protection. I'm changing the wiring to 10 guage for the hot, common wires plus the green ground.

Since the Ac system is isolated from the DC, I wonder if I should ground the green wire to my engine(my DC ground), or if the green wire returning back to the shorepower box will suffice, since the AC power is separated from the boat's DC wiring.

Are galvanic issues a realistic reason to keeping the AC ground from the DC ground?
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Old 22-06-2017, 23:40   #2
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Join Date: Dec 2011
Location: Tampa Fl
Boat: Catalina 36 / Morgan 33 OI
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Re: Isolated 120 Volt 30 Amp Service

Yes, use 30 amp box with dual pole disconnect main breaker ( hot and neutral) with 15 amp breakers for circuits and 10 gauge wires as you say. Do put in ground fault interrupters type outlets 'GFI' and keep the green wire separate and going to shore, isolated from the grounding wire.
As for the galvanic corrosion, look on fleabay for a marine isolator type box and install it across the green wire to shore.
No wire caps, use crimp connectors and put some putty caulk on the finished connectors to prevent corrosion, support all wiring well and not enclosed behind insulation or able to rub on things when in motion. Don't use Romex solid household wire for the service, it will eventually fatigue and break inside. Use stranded copper.
30 Amp service is enough for just the equipment you want to run simultaneously.
If you run the heater and a toaster or hotplate at the same time, the shore power may trip if it is also a 30 Amp breaker there, just shut off the heater when toasting or cooking.
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Old 23-06-2017, 00:26   #3
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Re: Isolated 120 Volt 30 Amp Service

Under abyc the green grounding wire must connect to the dc neg.

Otherwise it's possible if an ac wire touches metal in the boat. The whole boat and water will be live ac. And no breaker will trip without that bond wire. If you bond them, breakers would trip during that fault . Instead of killing people
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