Join Date: Jun 2007
Thanked 0 Times in 0 Posts
Rep Power: 0
credit goes to Art Richard IP32 #34 "Lagniappe" (St. Petersburg, FL) for the following dialogue:
"LOW GLOW OF REVERSE POLARITY LIGHT:
A low-level reverse polarity light on an IP when there is heavy current draw (like a heater or air conditioner) is not unusual. The reason is as follows:
1. The reverse polarity light is connected between the AC neutral (white) and AC ground (green) wires inside the distribution panel. If there is a voltage between these two lines, the light lights in proportion to the voltage.
2. When using shore power, the neutral and ground wires are connected together somewhere on the shore at a power distribution box. Between that point and your boat load (heater) are many feet of wire. Normally the AC current flows through the hot (black) wire to the load (heater) and back through the neutral (white) wire to the aforementioned distribution box (of course the current also flows through the black and white wire back to the power generator, but that is not pertinent to this discussion).
3. When current flows through a wire, the small resistance of the wire causes a voltage drop which is proportional to the length of the wire and the resistance of the wire. You see this on your AC voltage meter when you turn on a high current load (heater). Depending on the load and the length of wire, this voltage drop is sometimes 10 or more volts.
4. The reverse polarity lamp is effectively measuring the voltage between the neutral and ground wires at the boat. Since the ground wire is not (normally) carrying any current, there is no voltage drop in this wire. The neutral wire however is carrying current and does have a voltage drop. This voltage drop in the neutral wire appears across the reverse polarity lamp, causing it to glow, the brightness depending on the actual voltage drop in the neutral wire. This glow is not an indication of reverse polarity, and will not normally cause a problem.
BRIGHT GLOW OF REVERSE POLARITY LIGHT:
When you have a bright glow in the reverse polarity here is what happens:
1. In order for the bright glow to happen, there must be a high (about 100+ volts) voltage difference between the neutral and ground wires in your boat.
2. When the polarity is reversed, the power source's hot (black) wire is connected to the boat's neutral distribution, and the white (neutral) wire is connected to the boat's black wire. This can cause electrolysis and lots of other problems as well as being very unsafe. NEVER IGNORE A BRIGHT REVERSE POLARITY LIGHT! "
( Art continues with the following - not pertinent to your problem, but included anyway )
"YOUR GENERATOR PROBLEM:
Just because the generator does not light the reverse polarity light on another (non IP boat) does not prove that you do not have reverse polarity. It is hard to determine your problem without measuring voltages, but here are some possible causes:
1. Your generator has a reversed internal polarity. You need to measure the AC voltage between the neutral and ground pins on the generator output connector to verify this. On a "standard" (wall type) socket) the neutral is the wider flat slot and the ground is the round hole. If you get over 100 volts, the generator has reverse polarity. If you get a fluctuation in voltage, you probably have a floating ground.
2. Your generator has a floating ground (This can cause the reverse polarity light). If this is the case, you need to connect the neutral line to the ground (case) of the generator."
now back to sailnet:
for the problem you have of the indicator light, a question would be : is it totally off, low, or bright?
Clues to your situation are:
1) you're always plugged in at the dock - so with your batteries constantly topped, there would not even be a low glow (very faint perhaps) of the light.
2) when you replaced a dead battery and plugged in again, the system started working harder to get the bank up to specs. A low glow would be normal and actually shows everything is working OK. But the low glow would be a change from no light before and begs an explanation. Hopefully this is it.
3)before sailing, you have no light (batteries are topped, there's little draw), then after sailing, and perhaps using more amps than you made while underway, you plug in again - if a low glow is seen this is normal because you need to draw on you system to get back to full banks.
good luck. all the advice in the world doesn't mean you shouldn't get a reverse polarity tester and plug it in. cost is about 10 dollars at a hardware store.