Reverse Polarity Light

[mitiempo]

Any current drop should be equal between the hot and neutral wires - if not any GFI's would need resetting.

[donradcliffe]

Originally Posted by mitiempo

Any current drop should be equal between the hot and neutral wires - if not any GFI's would need resetting.

This is true, but not relevant. In the case with the long extension cord and the heater, you would have 120v between the hot and neutral at the house, and only 115v between the hot and neutral at the boat. The current induced voltage drop is equal in both the neutral and the hot wires, so the boat neutral would be 2.5v above ground and the boat hot would be 117.5v above ground. Try it and see for yourself.

[mitiempo]

Originally Posted by goboatingnow

The neutral is of course carrying the full circuit current , the ground does not carry current except under fault conditions.

Dave

But that is not what Dave is saying that I disagreed with.

[sabray]

if the light comes on the poles are reversed. you reverse the common and hot leads.

[mitiempo]

Originally Posted by sabray

if the light comes on the poles are reversed. you reverse the common and hot leads.

True, generally. Because it requires current in the neutral wire for that to happen.

[sabray]

yep that's the idea.If there is positive charge on the common side the light goes on,pokes reversed. Not so hard ehhh

[Lancerbye]

There are many misnomers in the electrical industry. Most have been brought about by people selling stuff and naming things that describe a product the way they want it sold with out regards for the trade. There is no such thing as reversed polarity wiring in an AC circuit. It is reversed feed with respect to ground. An AC source reverses polarity at 60 cycles per second in North America and some other parts of the world. The reversing of the High and neutral is a problem here because of the way our power distribution system works. We use the ground as a return path for AC distribution, thus saving us a lot of money in transmission line costs. Having spent 40 years in the trade certain terminology has always irritated me. This is one of them. Rant over.

[mitiempo]

Whatever you wish to call it it can be a problem if it is reversed.

On a properly wired boat the shorepower comes in to a double breaker that isolates both the hot and neutral wires. But the individual circuits only isolate the hot wire. If they are reversed and the breaker for any individual circuit is switched off the circuit is still hot.

[Hud3]

Side note: in a properly wired boat, the Reverse Polarity light may glow but not fully light up when a heavy load is applied, such as an electric water heater or charging flat batteries. No cause for alarm.

Investing in a polarity indicator is a wise use of a few bucks, just for the peace of mind.

[sdowney717]

We use the ground as a return path for AC distribution

ok so your telling me significant currents flow thru the ground?
If all the current is returning thru the dirt that does not seem possible.
what about the neutral return wires on the poles.

[fairbank56]

He's talking about the high voltage primary side of a power distribution system commonly known as SWER (single wire earth return). The secondary low voltage side that feeds your boat/house uses neutral for the return of the 120v legs.

Eric

[stewy]

Currently when at dock, when I connect an electric heater or turn on the microwave, which both draw high amperage, the reverse polarity light will begin to glow dimly. This also happens when on the hard connected to a long extension cord. Normally the reverse polarity light does not light up and I've checked the outlets in the boat with a plugin tester which indicates correct polarity. Should I be concerned with the boat wiring, or the shore power cord, or the shore power pedestal?

[donradcliffe]

Originally Posted by stewy

Currently when at dock, when I connect an electric heater or turn on the microwave, which both draw high amperage, the reverse polarity light will begin to glow dimly. This also happens when on the hard connected to a long extension cord. Normally the reverse polarity light does not light up and I've checked the outlets in the boat with a plugin tester which indicates correct polarity. Should I be concerned with the boat wiring, or the shore power cord, or the shore power pedestal?

The reverse polarity light is connected between the neutral and the grounding wire. If its starts to glow when you are pulling a lot of amps that means that there is a significant voltage drop along the neutral wire. It could be in the shore power cord, the boat wiring to the panel, or across any connector. If it was my boat, I would measure the voltage between the grounding wire and the neutral at several points--if there was a significant change (more than 2-3 volts), I would look for signs of a bad connection--corrosion and local overheating/melting.