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From: ahmet erkan (no email)
Date: Wed Dec 01 2004 - 21:05:00 EST
>In a message dated 11/23/2004 6:46:04 PM Eastern Standard Time,
> writes:
>I installed an inverter and connected it into my my
>main supply lines at the panel and before the main breaker for a single
>branch of my dual 30amp feeds. I installed a single 15amp breaker/switch in
>the panel to switch out the hot line of the inverter output, and wired the
>neutral and ground to the busses. At my home port everything works fine,
>but at a port with GFI circuit, it would trip every time I plugged in. When
>I disconnected the Inverter Neutral out from the panel, the circuit breaker
>was happy. Does this make sense? Should I just install another 15amp
>breaker with a bar and switch both the hot and neutral out of the boat's
>system?
>Any insights appreciated. Thanks
Hi,
There should always be virtually zero current in the ground wire. Shore
power with GFI breaker senses the current in the ground wire in a round
about way (ie: by sensing the difference in currents between Hot and Neutral
wires.) and the breaker trips if all of the current in the Hot wire does not
return through the Neutral wire except for a few milliamperes. One reason
for the shore GFI breaker to trip could be the proper design of your
inverter but poor documentation. The manufacturer ought to explain about
neutral to ground bonding. You see if the Inverter is operating when out at
sea, the Neutral should be at the same potential as the ground for safety
reasons and your inverter probably has the neutral and ground wires
internally hardwired. With the inverter neutral and ground connected all is
fine at sea, however when in port the Neutral terminal of the shore power
cannot be hardwired to the ground. If you short the Neutral and Ground wires
at the boat, the two wires will share the return current, and the GFI sensor
will detect a large difference between the Hot and Neutral wires and trip
the breaker.
What to do (IMHO) :
Your immediate problem I think is the neutral wire of the shore power routed
to the common ground in the inverter. You are right, opening both line and
neutral of the inverter is one way to do it. Hooking up one of Yandina's
galvanic isolators might also unload the ground wire and stop the tripping
but your boat will be hardwired to shore neutral so you want get any
anti-corrosion benefits.
I have some ideas about how to implement the "almost perfect" marine power
distribution system, with isolation transformers etc. A schematic in pdf
should be ready in a few months, if interested write to me off-list. Also,
you can interlock the inverter output with a contactor such that it will
automatically disconnect when shore power is present.
Good Luck,
Ahmet
sv8827
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