Kevin:

I have recently purchased a Honda EU 2000 generator to power the AC system on my Gemini 105 Mc.

I plug it into the boat through the regular 30 amp shore power input and all is well except that I get a red glow out of a diode on the circuit breaker panel indicating that the polarity of the input source is incorrect. This is of little concern to me since I know that the polarity is correct and, secondly, I read on a Gemini owners web site that other owners have observed this and use the generator anyway with no ill effects.

So what?

Well, I of course had to experiment and connected a wire from the external ground terminal of the generator to the common ground terminal of the diesel motor of the boat and interestingly enough my circuit breaker panel (Blue Seas Systems 360) showed a green light indicating proper polarity.

The circuit breaker panel instruction booklet avers that such a green light will appear only if three criteria are met simultaneously

1. There is a 120 V potential between hot and neutral,
2. A 120 V potential between hot and ground and
3. A 0V potential between neutral and ground.

I have determined that criteria 1) and 3) are met when measuring the output of the generator, but 2) is wanting because the potential between hot and ground is nominally 0 volts not 120 V.

So now to my question.

I notice on the wiring diagram of the generator that the grounding terminal on the AC output receptacle is common with both engine ground (generator engine that is) and frame ground. Why would connecting the external ground terminal to the boat engine, which I understand is common with all of the boat’s grounding, make the light go green?

Thanks for your consideration.

Bill

Bill,

It sounds like your AC grounding wire (green) is not making the proper connection.

For proper operation of your green and red indicator lights, the Neutral (white) and Ground (green) wire need to be connected together at the source of power (your generator or the AC distribution panel for your dock. When you connect the ground wire from your engine block to the chasis ground on your generator, you are completing the AC Grounding (green) circuit.

If you experience the same problem while plugged into a shore power connection, the problem is in your cordset, inlet, adaptor, galvanic isolator, etc.

If it is only while running the generator, the green wire from your outlet is not connected to the chasis ground on the generator.

Hope this helps.

Let me know if you have any questions,

Kevin

Kevin,

If the neutral and green are common on the boat and are not common on the generator then connecting the external ground on the generator to ground on the boat will in essence connect the white and green wire.

I never get a red light when plugged into shore power.

Thanks for your help!

Bill

Bill,

The Neutral and green should not be common on the boat. They are only connected at the source of power (your generator – the AC distribution center for the dock). If they are not connected at the source, you will get the “floating” effect on your ground. You will still see a voltage difference between the black and white of 120 vac, but the difference between the white and green and the black and green will vary.

Kevin