Reverse polarity

I'm flat out knowing my AC from my DC, Ohms from volts. So acknowleding this, my question is why does my circuit board on the IG have a Reverse Polarity light and what does it mean in practical terms if it comes on?

practical terms if it comes on?

ON an AC circuit it can mean your ground wire is lost or reversed and you could get line voltage thru your body with some appliances.

On my current boat, an insurance survey had me add one. On my past boat, it went off once when I plugged into a homeowners shore power outlet. I just disconnected and ran the genset when needed.

This came from another forum:*
The most important issue is whether the power supply polarity is correct.* If reversed, the Neutral and Hot legs are switched. Then all your breakers interrupt the Neutral, not the Hot, so your whole system is energized even when the breaker is off. The breaker will turn of the equipment, but it is still energized. A fault can then start a fire, since the breaker won't sense the ground fault, and current will flow until something melts and the circuit is broken. There's also the danger of electrical shock, for the same reason.

Always, always check this light after connecting to shore power but immediately before or immediately after flipping the transfer switch from "genset" to "shore", depending how your boat is wired. Do not ignore the fault light. Disconnect immediately and find out what the problem is.

How do I know this? Let's just say, good judgement comes from experience and experience is the result of bad judgement. We were having intermittent problems with the fault light coming on occasionally at one particular dock. I ignored it and the the problem turned out to be a faulty neutral connection in the male plug of our shore cord. I guess something about the way the cord hung from that particular box caused the problem to show up.

We got lucky. Toasted male plug that needed to be replaced, blown breakers, and no damage from the freezing temperatures of that two week period the boat sat at the dock. And no deaths.

At least, none that could be traced to us.

We were required by the insurance company to bring the Eagle up to ABYC standard which requires a DOUBLE throw breaker with polarity light installed between the boat shore plug out let and the main power panel AC selector switch.* Many electrical fire are between the shore power plug/cord and the AC breaker which*on many boats is after*the AC selector switch.** A*DOUBLE throw breaker is required so if the polarity is reversed*it will still break*

Ok thanks for that everyone. So the Reverse polarity light is a warning indicator that all is not well.

FF" ON an AC circuit it can mean your ground wire is lost or reversed and you could get line voltage thru your body with some appliances."

Does this mean that the ELCB (Earth trip switch) will fail to trip?

I am not aware of the ground wire being disconnected by any type of breaker.

The usual 2 breaker wires cut are the hot and neutral in most panels ..

I think I posted this once, a while ago, but maybe worth repeating.* I have one of these gizmos plugged into an* AC outlet to check every time I hook up shore power

Does this mean that the ELCB (Earth trip switch) will fail to trip?


Are you referring to a GFI "Ground Fault Interupter?

ARoss wrote:
I think I posted this once, a while ago, but maybe worth repeating.* I have one of these gizmos plugged into an* AC outlet to check every time I hook up shore power

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*So, let me get this straight. On the one hand, we have a $100 added-feature light soldered into an expensive marine power panel that usually only indicates one failure mode. On the other hand, we have an $8 gadget carried by every residential electrician in North America that actually gives better information on more failure modes than the panel light does.

I dunno, seems lacking a certain je ne sais quois. I might have to set fire to a few $20s when I pick one up tomorrow just to make things feel right.

Sisuitl wrote:*On the other hand, we have an $8 gadget carried by every residential electrician in North America that actually gives better information on more failure modes than the panel light does.

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*That isn't quite a fair evaluation. The built in reverse polarity warning tells you if the shore power is improperly connected. The little outlet tester tells you if the outlet you are about to use is connected properly.

The reason every residential electrician in North America carries one is because there is no way to look at an outlet and tell if it is wired properly. The same applies to a boat.

On the one hand, we have a $100 added-feature light soldered into an expensive marine power panel that usually only indicates one failure mode. On the other hand, we have an $8 gadget carried by every residential electrician in North America that actually gives better information on more failure modes than the panel light does.

Yup,

Making 50 million of something in China is always cheaper than hand assembling one of anything anywhere.

FF wrote:
On the one hand, we have a $100 added-feature light soldered into an expensive marine power panel that usually only indicates one failure mode. On the other hand, we have an $8 gadget carried by every residential electrician in North America that actually gives better information on more failure modes than the panel light does.

Yup,

Making 50 million of something in China is always cheaper than hand assembling one of anything anywhere.

*

It's not a "$100.00 added in feature", it's part of any modern marine electrical panel.* It is not possible to put a specific cost on this feature.

As far as it's purpose, it's been said several different ways, but the bottom line is, there is a problem with the power source (dock power or portable generator) that needs to be corrected immediately.* Disconnect the boat from the source untill the problem is corrected.

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