Hello Kevin,

My question is regarding marine wiring.

On my marine electrical, I’m using an isolation transformer in order to transform 220V to 110V.

Recently, the boat’s reverse polarity indication light is on. I’ve opened the circuit to see how this indication is measured and saw that there is a diode and led connected between the neutral and the ground.

I’ve realized that in the current situation the output of the transformer is basically floating, therefore the neutral line can have any voltage. One of the solution that I’ve seen online is connecting the neutral line at the output of the transformer to the boat’s ground (that is not connected to the shore’s ground). So I have several questions about it:

1. Is there advantage in connecting the neutral to the boat’s ground over working with floating voltage?
2. Is it ok to make this connection?
3. For about a year, the indication was off, what can be the cause for it to be on now?

Thanks in advance,

Ilia

Hi Ilia,

At the source of power, the neutral must be connected to the ground. With an isolation transformer, this is on the output (boat size). Please connect the output neutral and ground together immediately. It is an extreme shock hazzard as is.

The reverse polarity indicator is connected to the input side of your transformer. With an isolator transformer, the light is more of a nuisance than a concern. It is telling you that the polarity is reversed (Neutral is hot) on the input. Since you have an isolation transformer, you really don’t care as long as the neutral and ground are connected together on the output side.

Hope this helps,

Kevin

Hi Kevin

I’m working on a 32 foot cruiser. I’ve rewired the whole boat and can’t get the DC side of the panel to work “lights or anything”.

I was wondering if the generator has to be on? Also shore power #2 isn’t working, #1 works fine and will run the AC side of the panel.

I’m stumped on the DC side though, it is strange to me if it’s not the generator. I’m kind of lost if you could please help? I need some.

Thanks,

Barry

Hi Barry,

Marine electrical DC power should have nothing to do with the generator.

Using a meter, start at the source of power, the battery, and make your way to the DC panel to find the problem. It is probably a bad ground connection or loose circuit breaker wire that is causing the problem with the boat wiring.

If you are not experienced with marine AC wiring, I would hire an electrician. It is easy to make a fatal mistake and then you wouldn’t be able to write back and tell me what was wrong…

Looking forward to hearing from you!

Kevin

Kevin,

My boat wiring currently has a shore power charging system, and an alternator on the diesel.

I would like to add a 100 watt solar panel with regulator. How do I wire it to ensure that the three charging sources aren’t potentially “tripping” over each other if they happen to get used at the same time?

Thanks!

Stephen

Stephen,

Your batteries act as a giant filter.

Most marine electrical charging devices won’t trip over each other. When the engine is running, the alternator will be the dominate charging device. When plugged in, the charger will be in control. While on the anchor, the solar system will do all of the charging.

Hope this helps,

Kevin