Shore Power Problems


I own a boat bought from the US (110V) and transported via container to Greece (220V) where I reside. It has two shore AC input lines (30amp each) and a generator. The source selection switch is a Kraus-Naimer C42-C17591 3 position switch (Line 1 - Line 1&2 - Gen. )

I wanted to retain the original 110VAC configuration, so I used a 220 to 110V transformer (Seven Star ATVR8000) before the main AC selection switch. All the connections were made by an experienced electrician.

When I use the generator as my 110VAC source everything works perfectly. When I use either the 1st or both shore power lines something goes wrong. Most of the times the dock's power center anti-electric shock breaker "drops". The dock power center terminal has an installed anti-electric shock breaker for safety reasons which cannot be removed by any means. Two or three times for an unknown reason the breaker didn't "drop" and I noticed that some electrical appliances from the 1st AC panel (eg water heater, air condition) worked while others didn't (eg Microwave oven, all the inside wall-plugs). Nothing from the 2nd AC panel ever worked, because when I try to switch on the main 2nd AC panel switch, it "drops" automatically.

The shore line power worked fine in the US, but I found out that the dock power center there, didn't have anti-electric shock breaker installed. The 220 to 110VAC transformer works fine when I connect it directly to a 110Vac device (eg a fan). The transformer's breaker never "dropped". The cable connections to the main ac selection switch were checked, confirmed and are correct.

I also tried a different dock power terminal, but the same problem insisted. Could the problem be a minor electric leak somewhere in the system, which the generator is able to overcome while the dock power center cannot, and if that's true how can I locate and fix this problem? The ground bus terminal is connected with the DC bonding system and there is a galvanic isolator/zinc saver somewhere in the ground wire system.

The electrician also tried uninstalling the galvanic isolator and tested the system without connecting the green AC ground wire but nothing changed (again the dock's anti electric shock breaker "dropped").
We have tried numerous other tests but didn't accomplish anything. We cannot locate the problem so any help or suggestions would be welcome.
Thank you in advance.

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Jan 30, 2008
shore power problem
by: Anonymous

first of all your boat doesn't have a 120/240 split system. 30amp shore powers are 110v. you have to have a isolation transformer, but you would need two. and connect the neutral and ground on the secondary side.

Sep 08, 2007
GFCI & AutoTransformers
by: Nate

The root of your problem with the dock breaker tripping is most likely that the transformer you have selected is an autotransformer. Autotransformers have a common primary/secondary winding, thus forcing a connection between ground and neutral on the boat side when wired correctly. If this is the case, you must replace it with an isolation transformer. In wiring, be sure that the incoming safety ground is connected to the transformer case and the boat's safety ground IS NOT. The boat's safety ground is connected to the designated neutral at the transformer secondary. A transformer secondary and a generator are the ONLY places on a boat where a connection is made between safety ground and neutral. Your boat has a split 120/240 volt system, so your transformer must have a 120/240 secondary winding.

Incidently, there SHOULD be ONE connection between the main busses of the boat's DC (-) and AC safety ground.

Sep 08, 2007
Shore Power Solution
by: Frank

I just popped in after years of absence and saw this post.

The RCD or GFI detector works on the measurement of current flowing from the live wire to the load and back through the neutral wire. If a difference or loss of current exceeds 30milliamps there is an unbalance and the RCD trips. it is assuming this missing current is electrocuting someone!

It is possible you have the earth and the neutral bonded together at the transformer primary. It is common practice to join earth and neutral. The reason being it 'ties' the neutral to zero volts and stops it floating.
This is because the only place the neutral is at zero volts is at an earth point.
What you are experiencing is current going to earth and not going back through the neutral. Just check with multimeter if neutral and earth are joined at the shore plug.

As for the frequency it causes problems with synchronous equipment such as AC clocks and completly changes the impedance of electric motors.

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