Thanks to all who responded and especially Ken who cleared it all up. My CD25D's stock AC panel works like Ken's. The switch associated with Reversed Polarity is to test the LAMP only. The lamp is across GND and Neutral unless the switch is flipped, then it's across GND and HOT. Think about it. What good is a lamp that by design indicates a "GOOD" condition by being "OFF" if you can't EASILY test to verify that the lamp is NOT burned out. NOT MUCH!! Talk about a lawyers dream case!
randy.bates@baesystems.com
CD25D AC Panel
Moderator: Jim Walsh
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Larry DeMers
Re: One Thing....
Ken,
You say there is "significant current flow all the time". WHere is the flow from? If the bulb is not lit, and it is a good bulb, that means that the bulb is not seeing a sufficient voltage differential to light the light, correct?
When the bulb is out, it means that the wires it is connected to are at the same or close to the same potential. In this case, that means that Ground and Neutral are the two lines in question now. They are properly tied together at the dock service box, so there should be no voltage between them, as *effectively* they are the same wire.
There is no current going into the underwater metal at this point.
Now say our boat owner has a bad day and rewires his boat one saturday, and accidently reverses Line (black) and Neutral (white). Now he goes down below and sees the "Polarity Reversed" Indicator is lit. Now that incandescent light will be across ground and line, sine the neutral and line were reversed. It will light..but if the ground is indeed intact, the current will be returning via the ground wire, not the water. There is no "Significant flow of electricity" in this case either.
Now say our boat owner has a really bad day, and somehow opens up ground and also reverses Line and Neutral. He walks down below, and notices that the "Reverse Polarity" light is lit. Now what is happeneing? Since the ground in this case, is open, and Line and Neutral are reversed too, the "Reverse Polarity light may or may not light at all..depends on where the Ground Fault happened. If it happened prior tot he point where ground and neutral were tied together, then the ground wire is floating in mid air..not connected to anything, and the Reverse polarity light will not light. Again, there is no "significant amount of current going into the water" in this case. In the example used here, the light IS lit, so the ground fault has to be after the Neutral to Ground tie in the dock service box. Now the return path for the "Rev. Polarity light" is the neutral wire, still connected. The light will light, and there is no significant electrolysis current flowing here either.
Remember that just because there is a parallel connection to the ships bonding system, current still takes the path of least resistance. Water is highly resistive compared to a copper cable in good shape, so the current will follow the cable as the return path, not the water. There is however, a very small portion of current that would flow in this case due to the water being a high resistance parallel path. It is not in the range ordinarily understood to cause electrlysis though. For this discussion, the parallel effect can be ignored, and the major path only considered. If you set up a condition where the return path is interrupted and you have a device using 120vac, it's return path could be thru the water, and that itself would be a consideration for possible electrolysis.
But to return to the Reverse Polarity Switch question, I do not see where there can be any current flow to the water in this circuit as designed, without the switch installed. I think the switch may be to actually provide a testing capability of that rev. polarity light..not activate it for testing.
If anyone can see what I am missing, please speak up and show me where you think the current is going and how. At this point, I am convinced that this topic was a bit of overreaction to start with, and escalated into a misunderstanding of how the grounds and rev.polarity circuit works.
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30 Lake Superior
demers@sgi.com
You say there is "significant current flow all the time". WHere is the flow from? If the bulb is not lit, and it is a good bulb, that means that the bulb is not seeing a sufficient voltage differential to light the light, correct?
When the bulb is out, it means that the wires it is connected to are at the same or close to the same potential. In this case, that means that Ground and Neutral are the two lines in question now. They are properly tied together at the dock service box, so there should be no voltage between them, as *effectively* they are the same wire.
There is no current going into the underwater metal at this point.
Now say our boat owner has a bad day and rewires his boat one saturday, and accidently reverses Line (black) and Neutral (white). Now he goes down below and sees the "Polarity Reversed" Indicator is lit. Now that incandescent light will be across ground and line, sine the neutral and line were reversed. It will light..but if the ground is indeed intact, the current will be returning via the ground wire, not the water. There is no "Significant flow of electricity" in this case either.
Now say our boat owner has a really bad day, and somehow opens up ground and also reverses Line and Neutral. He walks down below, and notices that the "Reverse Polarity" light is lit. Now what is happeneing? Since the ground in this case, is open, and Line and Neutral are reversed too, the "Reverse Polarity light may or may not light at all..depends on where the Ground Fault happened. If it happened prior tot he point where ground and neutral were tied together, then the ground wire is floating in mid air..not connected to anything, and the Reverse polarity light will not light. Again, there is no "significant amount of current going into the water" in this case. In the example used here, the light IS lit, so the ground fault has to be after the Neutral to Ground tie in the dock service box. Now the return path for the "Rev. Polarity light" is the neutral wire, still connected. The light will light, and there is no significant electrolysis current flowing here either.
Remember that just because there is a parallel connection to the ships bonding system, current still takes the path of least resistance. Water is highly resistive compared to a copper cable in good shape, so the current will follow the cable as the return path, not the water. There is however, a very small portion of current that would flow in this case due to the water being a high resistance parallel path. It is not in the range ordinarily understood to cause electrlysis though. For this discussion, the parallel effect can be ignored, and the major path only considered. If you set up a condition where the return path is interrupted and you have a device using 120vac, it's return path could be thru the water, and that itself would be a consideration for possible electrolysis.
But to return to the Reverse Polarity Switch question, I do not see where there can be any current flow to the water in this circuit as designed, without the switch installed. I think the switch may be to actually provide a testing capability of that rev. polarity light..not activate it for testing.
If anyone can see what I am missing, please speak up and show me where you think the current is going and how. At this point, I am convinced that this topic was a bit of overreaction to start with, and escalated into a misunderstanding of how the grounds and rev.polarity circuit works.
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30 Lake Superior
Ken Coit wrote: However, I suspect that part of the confusion is coming from other "Reverse Polarity" circuits that employ two indicators, one on the line and one on the neutral lines. These are usually arranged like the testers we find at the hardware store, with one red light and one green light, the intent being that green is good and any presence of red is bad whether with or without green. If the two indicator "Reverse Polarity" circuit is used with neon bulbs, it is still not a problem, but with incadescents, there is significant current flow all the time and there may well be significant electrolysis. I think in that case, I would like a switch to disconnect the "Reverse Polarity" circuit from safety ground, but I prefer the stock circuit found on CD/36s: one neon bulb which is normally across the neutral and safety ground lines with a momentary switch to connect the bulb to the hot line for testing the bulb. The pilot light is across the hot and neutral lines with no breakers between it and the pier; it is always on if we are on the grid.
Keep on sailing,
Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC
demers@sgi.com
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Ken Coit
Re: One Thing....
Larry,
Again, a very thorough analysis; you are wonderful!
First of all, to the best of my knowledge, Parfait and other Cape Dorys do not employ the circuit I was discussing, so this is really an academic exercise to keep us from doing something less meaningful.
I was speculating with a hypothetical about two-bulb incadescent reverse polarity circuits where there will always be current flowing through one or the other of the bulbs. Since it is my hypothetical, I'll suggest that maybe 150 ma. is flowing all the time that AC is connected to the boat and the circuit is energized. Where it goes is the crux of the question. Without a reversal, it goes through the neutral lead and is no problem. With a reversal, the current goes through the neutral and safety ground and it can be a problem.
If the boat is wired per ABYC, with the safety AC ground (green) connected to the DC ground, and DC ground is connected to the water via thru-hulls, prop shaft, etc., then there is the possibility that if the safety ground is broken at the dockside and there is simultaneously a reversal of neutral and line, that the 150 ma. will try to flow through the water. If it does, it will cause problems somewhere.
To eliminate this failure mode, all one needs to do is to turn the reverse polarity circuit off when it isn't needed, like when you are not on board. That was my only point in suggesting that a switch be included in a two bulb incadescent reverse polarity circuit.
An alternative recommended by many, is to not leave the boat connected to the AC mains when you are not on board.
Thanks for your continuing thorough analyses.
Ken
parfaitNOSPAM@nc.rr.com
Again, a very thorough analysis; you are wonderful!
First of all, to the best of my knowledge, Parfait and other Cape Dorys do not employ the circuit I was discussing, so this is really an academic exercise to keep us from doing something less meaningful.
I was speculating with a hypothetical about two-bulb incadescent reverse polarity circuits where there will always be current flowing through one or the other of the bulbs. Since it is my hypothetical, I'll suggest that maybe 150 ma. is flowing all the time that AC is connected to the boat and the circuit is energized. Where it goes is the crux of the question. Without a reversal, it goes through the neutral lead and is no problem. With a reversal, the current goes through the neutral and safety ground and it can be a problem.
If the boat is wired per ABYC, with the safety AC ground (green) connected to the DC ground, and DC ground is connected to the water via thru-hulls, prop shaft, etc., then there is the possibility that if the safety ground is broken at the dockside and there is simultaneously a reversal of neutral and line, that the 150 ma. will try to flow through the water. If it does, it will cause problems somewhere.
To eliminate this failure mode, all one needs to do is to turn the reverse polarity circuit off when it isn't needed, like when you are not on board. That was my only point in suggesting that a switch be included in a two bulb incadescent reverse polarity circuit.
An alternative recommended by many, is to not leave the boat connected to the AC mains when you are not on board.
Thanks for your continuing thorough analyses.
Ken
Larry DeMers wrote: Ken,
You say there is "significant current flow all the time". WHere is the flow from? If the bulb is not lit, and it is a good bulb, that means that the bulb is not seeing a sufficient voltage differential to light the light, correct?
When the bulb is out, it means that the wires it is connected to are at the same or close to the same potential. In this case, that means that Ground and Neutral are the two lines in question now. They are properly tied together at the dock service box, so there should be no voltage between them, as *effectively* they are the same wire.
There is no current going into the underwater metal at this point.
Now say our boat owner has a bad day and rewires his boat one saturday, and accidently reverses Line (black) and Neutral (white). Now he goes down below and sees the "Polarity Reversed" Indicator is lit. Now that incandescent light will be across ground and line, sine the neutral and line were reversed. It will light..but if the ground is indeed intact, the current will be returning via the ground wire, not the water. There is no "Significant flow of electricity" in this case either.
Now say our boat owner has a really bad day, and somehow opens up ground and also reverses Line and Neutral. He walks down below, and notices that the "Reverse Polarity" light is lit. Now what is happeneing? Since the ground in this case, is open, and Line and Neutral are reversed too, the "Reverse Polarity light may or may not light at all..depends on where the Ground Fault happened. If it happened prior tot he point where ground and neutral were tied together, then the ground wire is floating in mid air..not connected to anything, and the Reverse polarity light will not light. Again, there is no "significant amount of current going into the water" in this case. In the example used here, the light IS lit, so the ground fault has to be after the Neutral to Ground tie in the dock service box. Now the return path for the "Rev. Polarity light" is the neutral wire, still connected. The light will light, and there is no significant electrolysis current flowing here either.
Remember that just because there is a parallel connection to the ships bonding system, current still takes the path of least resistance. Water is highly resistive compared to a copper cable in good shape, so the current will follow the cable as the return path, not the water. There is however, a very small portion of current that would flow in this case due to the water being a high resistance parallel path. It is not in the range ordinarily understood to cause electrlysis though. For this discussion, the parallel effect can be ignored, and the major path only considered. If you set up a condition where the return path is interrupted and you have a device using 120vac, it's return path could be thru the water, and that itself would be a consideration for possible electrolysis.
But to return to the Reverse Polarity Switch question, I do not see where there can be any current flow to the water in this circuit as designed, without the switch installed. I think the switch may be to actually provide a testing capability of that rev. polarity light..not activate it for testing.
If anyone can see what I am missing, please speak up and show me where you think the current is going and how. At this point, I am convinced that this topic was a bit of overreaction to start with, and escalated into a misunderstanding of how the grounds and rev.polarity circuit works.
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30 Lake Superior
Ken Coit wrote: However, I suspect that part of the confusion is coming from other "Reverse Polarity" circuits that employ two indicators, one on the line and one on the neutral lines. These are usually arranged like the testers we find at the hardware store, with one red light and one green light, the intent being that green is good and any presence of red is bad whether with or without green. If the two indicator "Reverse Polarity" circuit is used with neon bulbs, it is still not a problem, but with incadescents, there is significant current flow all the time and there may well be significant electrolysis. I think in that case, I would like a switch to disconnect the "Reverse Polarity" circuit from safety ground, but I prefer the stock circuit found on CD/36s: one neon bulb which is normally across the neutral and safety ground lines with a momentary switch to connect the bulb to the hot line for testing the bulb. The pilot light is across the hot and neutral lines with no breakers between it and the pier; it is always on if we are on the grid.
Keep on sailing,
Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC
Ken Coit wrote:
parfaitNOSPAM@nc.rr.com
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John R.
Let's try again.......
There is a little more detail to the story please see retort comments below, I certainly hope matters are clarified:
Larry: : Hi Everyone,
Larry: Here is the description of how this circuit operates and why it cannot be a source of "stray current" electrolysis under normal conditions:
You just revealed the potential problem.
Larry: This Reverse Polarity light is connected between the Neutral and Green Wire Grounds of the incoming 120vac service cable. In normal conditions..ie: no faults, there is and can be *no* voltage impressed across this lamp, therefore no current flows, and there can be NO stray current issue here, since it is essentially a dead circuit.
John: The *power indicator light* has one hot leg and one neutral leg, power comes in on the hot leg. The neutral leg of that indicator lamp (which carries returning current) connects to the *line terminal* of the neutral circuit breaker along with one leg of the reverse polarity indicator light (This is the problem). The other leg of the reverse polarity light goes to ground.
When a boat has a onboard AC safety ground (green wire)to the boats common ground point (engine , dynaplate etc) then returning current from the power indicator light will follow the neutral and ground to all points of ground. That means it can go back to shore via the ground or neutral or can go to the water (or via all three)and does cause stray current problems when current enters the water. This is based on a boat wired to ABYC standards.
Now at this point some will say there is an easy solution, just disconnect or don't have an on board AC safety ground circuit that doesn't return to shore only. I suppose that would be okay if you totally trusted the integrity of every ground connection at every marina and shore side hook up. In my eyes (an evidently ABYC's) that is being naive and careless. If a short occurs on board in any AC appliance including the boat inlet components, transfer switches, etc then you could quite frankly be electrocuted if there is not a safety ground that has full integrity to handle a short. That is why ABYC guidelines stipulate a onboard AC safety ground be wired to a vessels common ground point. Now, having said that...by doing this you then open the opportunity for the reverse polarity light stray current entering the water (the returning power indicator current). A momentary switch installed between the reverse polarity indicator light and the ground prevents that stray current scenario.
Furthermore for those who don't like the AC ground standards that ABYC advocates and do not want to incorporate their electrical recommendations just keep in mind if you run a generator set or an AC inverter on board you basically have no safety ground on your AC distribution system because you are no longer hooked to a shoreside connection.
Larry: There the Rev. Polarity lamp will light is if there is a voltage difference between it's two leads, which then means that there will be a current flow from one lead, thru the filament of the lamp to the other lead.
Larry: This, by the way, *is not* stray current, but rather direct AC current. There IS no stray current possible in any configuration of this circuit.
John: In your scenario Larry that is true but in the scenario I have outlined that is not the case because the power indicator is always illuminated when hooked to shore in a typical AC distribution panel installation.
It is stray current.
Larry: Stray current is current that flows even when the circuit is turned off, and that clearly would be impossible in this circuit since under normal circumstances, the lamps two leads are connected to essentially the same wire (as the Neutral and Ground wires are -once again, shorted together at the service terminal on the dock).
John: And Cheers to you Larry.
I hope this stuff is all clarified. I have a feeling many folks are probably pretty darned confused by now. It is so simple to illustrate but difficult to discuss.
Please note: If memory serves some CD owners manuals will show an AC circuit schematic but probably will not indicate an onboard AC safety ground except the one afforded by the shore side cable. Therein is where the safety and stray current issues arise. The CD schematic I'm familiar with does not meet ABYC (American Boat and Yacht Council) standards.
If someone notes errors in my or Larrys comments please point them out.
Larry: : Hi Everyone,
John: Good observation but not always true, there is the *other* "condition". Some panels may be fine and some not. I never ever said all CD panels need the momentary switch, if memory serves I indicated that owners should check their panels and see if it was necessary. Like I said in a previous post to you the AC return current is the problem. I should at this time make perfectly clear that if the boat does not have an ABYC recommended vessel safety ground then it would not be necessary because the neutral and safety ground return to shore. Some CD's have this and some do not. If a boat is wired in accordance with ABYC electrical standards (which some CD AC services are not)and has an AC safety ground to the vessels common ground point then there is a stray current problem if the vessel is using an incandescent reverse polarity lamp.Larry DeMers wrote: I was thinking about the warning that John R. gave us about the reverse polarity light needing a switch to break a "stray current path" that could result in increased current pressure on the bonded parts of the boat, which might increase your electrolysis potential, and have come to a point where I doubt that this is true under all but one circumstance.
This warning that JohnR gave us would be valid IF you lost both the Neutral AND Ground lines to the service terminal on the dock. Under no other condition can I see where *any* current can flow thru the reverse polarity light to ground or neutral (essentially these two are tied together at the dock, so they are and should be the same). This means that the panels you have without the switch are fine.
Larry: Here is the description of how this circuit operates and why it cannot be a source of "stray current" electrolysis under normal conditions:
John: YES, including the AC power indicator light (a device)!Larry DeMers wrote: You have 3 wires coming in to your boat; Line (which is the hot wire), Neutral (which is the return path for any 120vac used by a device onboard)
You just revealed the potential problem.
Larry: This Reverse Polarity light is connected between the Neutral and Green Wire Grounds of the incoming 120vac service cable. In normal conditions..ie: no faults, there is and can be *no* voltage impressed across this lamp, therefore no current flows, and there can be NO stray current issue here, since it is essentially a dead circuit.
John: The *power indicator light* has one hot leg and one neutral leg, power comes in on the hot leg. The neutral leg of that indicator lamp (which carries returning current) connects to the *line terminal* of the neutral circuit breaker along with one leg of the reverse polarity indicator light (This is the problem). The other leg of the reverse polarity light goes to ground.
When a boat has a onboard AC safety ground (green wire)to the boats common ground point (engine , dynaplate etc) then returning current from the power indicator light will follow the neutral and ground to all points of ground. That means it can go back to shore via the ground or neutral or can go to the water (or via all three)and does cause stray current problems when current enters the water. This is based on a boat wired to ABYC standards.
Now at this point some will say there is an easy solution, just disconnect or don't have an on board AC safety ground circuit that doesn't return to shore only. I suppose that would be okay if you totally trusted the integrity of every ground connection at every marina and shore side hook up. In my eyes (an evidently ABYC's) that is being naive and careless. If a short occurs on board in any AC appliance including the boat inlet components, transfer switches, etc then you could quite frankly be electrocuted if there is not a safety ground that has full integrity to handle a short. That is why ABYC guidelines stipulate a onboard AC safety ground be wired to a vessels common ground point. Now, having said that...by doing this you then open the opportunity for the reverse polarity light stray current entering the water (the returning power indicator current). A momentary switch installed between the reverse polarity indicator light and the ground prevents that stray current scenario.
Furthermore for those who don't like the AC ground standards that ABYC advocates and do not want to incorporate their electrical recommendations just keep in mind if you run a generator set or an AC inverter on board you basically have no safety ground on your AC distribution system because you are no longer hooked to a shoreside connection.
Larry: There the Rev. Polarity lamp will light is if there is a voltage difference between it's two leads, which then means that there will be a current flow from one lead, thru the filament of the lamp to the other lead.
John: Only in the case of a boat that does not meet ABYC electrical standards.Larry DeMers wrote: So for the lamp to light in our boats, we have to have a situation where there is a voltage difference between neutral and ground. Remember that these two wires started out shorted together back on the dock, right?
The condition that will cause this to happen is where Line (the hot wire) and the Neutral (return) wire were swapped at the dock or in the boats 120vac wiring. Here, the lamp WILL see Line voltage (hot) on one filament lead instead of Neutral (essentially ground). The other lamp lead remains connected to Ground. Now we have a voltage difference between the two leads..120v of difference, and the lamp will light.
These are the only situations where the lamp should lite I believe.
Now for "stray current" electrolysis to happen, the Neutral and the ground connections to shore must be open, and you must have a reversed polarity situation on the cable also. That is a three point failure in the 120vac service to your boat, and it probably would not happen in 5 lifetimes! Even if it did, you would certainly be aware of it, as the 120vac would not work properly, since the return path would be thru the boats underwater bonding and metal fittings to shore ground rod..a very long way aways from the boat usually, so that means resistance, which means the voltage would be far less than 120vac at your appliance, and it would not work like normal. SO you would be aware of something wrong. The reverse polarity light would also be on, and here is where John is correct. The current thru the light, about 120ma, would run thru the bonding system to the underwater features on your boat, to the shore ground rod.
**That will cause some electrolysis for the time that the reverse polarity light is on only.**
So to get to this position of electrolysis, we need a triple failure of the 120vac system onboard or at the dock. the damage would only occur while the reverse polarity light was actually on.
Larry: This, by the way, *is not* stray current, but rather direct AC current. There IS no stray current possible in any configuration of this circuit.
John: In your scenario Larry that is true but in the scenario I have outlined that is not the case because the power indicator is always illuminated when hooked to shore in a typical AC distribution panel installation.
It is stray current.
Larry: Stray current is current that flows even when the circuit is turned off, and that clearly would be impossible in this circuit since under normal circumstances, the lamps two leads are connected to essentially the same wire (as the Neutral and Ground wires are -once again, shorted together at the service terminal on the dock).
John: And Cheers to you Larry.
I hope this stuff is all clarified. I have a feeling many folks are probably pretty darned confused by now. It is so simple to illustrate but difficult to discuss.
Please note: If memory serves some CD owners manuals will show an AC circuit schematic but probably will not indicate an onboard AC safety ground except the one afforded by the shore side cable. Therein is where the safety and stray current issues arise. The CD schematic I'm familiar with does not meet ABYC (American Boat and Yacht Council) standards.
If someone notes errors in my or Larrys comments please point them out.
Larry DeMers wrote: Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30
Lake Superior
Randy Bates wrote: Should the AC indicator light come on as soon as the shore power cord is connected or does the main CB need to be switched on?
Is the "AC reversed" light function active as soon as shore power is connected? IE, if NOT reversed, NO light. Is the switch associated with the "AC Reversed" light a test switch for the light NOT for a reversed AC condition?
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Larry DeMers
Re: One Thing....
Hi Ken,
I have our boat wired per the NFP codes, rather than the ABYC, which means that I do not have the green safety ground wired to my DC bonding or engine..only to devices that actually use 120vac, such as the inverter/charger. This connection in the charger is actually relay switched when it is in operation, so it is bonding the two grounds together when using the Inverter but not during charging. But I am not realy concerned here with bonding but the reverse polarity switches, and specificly Johns admonition about a series switch being needed.
I am relieved to hear that you read my long reply and understood what I was trying hard to say, and that you essentially agree with it. Now to your concern about the Electrolytic Current that the triple failure of A) Reversed Polarity between Line & Neutral B) Simultaneous failure of Ground at the Dock Service box and C) Simultaneously a 120vac device in the boat that is plugged in, turned on and fails with a short of the windings or one or either of Line and Neutral to a conductive area of the case, which is usually made of cheap plastic anyway, occurs. 120 ma of current will then certainly flow through the Rev. Polarity Lamp filament, and into ground, -water in this case, causing some mild electrlysis if alllowed to persist for months..or certainly weeks if this worsens an already electrolytic situation.
Your concern is one to be aware of. But guys, I have worked with statistical analysis for probably 20 years now, in determining likelyhood of a failure in a multi-milllion (transistors)gate array for our computers. The likelyhood of all of those things coming together and happening simultaneously is so very miniscule as to be a statistical zero. Additionally, an observant guy like you will certainly notice that the 120v device is not running nearly as fast as before, since the water is a poor ground, electrically. Wire is far, far better. So there will be the increased resistance to operate thru which drops the available voltage to the 120vac device, and which then operates the device much slower. It could also blow a 15Amp DC breaker (House Panel) on start up if it was an inductive load like a motor due to the voltage drop of water..especialy 1000's of feet of it to reach the shore ground rod. You will notice it if you are present when it operates.
So the problem should be self-evident if this mountain of bad luck befalls one. But the addition of a switch would certainly not relieve you of any of this so far..not a bit.
It would cut out that 120ma of current that would flow only during the time of this triple-whammy, this penultimate of accidents and random bad luck, all happening at once. No possibility of a rev. polarity light then...of course,
But the danger that you are being exposed to in exchange is far greater! Should that switch be left off accidently while the 120vac is in operation, you have given up your protection *from* Reversed Polarity events. This will then open you to possible lethal shock from simply touching the wrong 2 items on your boat..like holding on to your shrouds, while talking to the neighbor, who leans across to shake your hand..oh, he' s hanging onto his shrouds also!..Zap..two nice guys leave for the other side..and the lawyers line up in the aisles..
So if a guy were clever, he could combine a Rev.Polarity light test function with a spring return to center off, DPDT switch. Throw it one way, it lights the lamp for you assuring you that yes indeed it works now. Throw it the other, and the light will be taken out of the circuit totally until it is turned on manually.
Ahhh..see the problem with this thought?
Ok, so Joe Schmo decides he is going to prevent this dastardly "Stray" current from eating his beauty alive, so he throws the switch opening the circuit to the warning light, disabling it.
Suppose he forgets to check it one weekend, and low and behold grandpa Silly dies over the next weekend so there is the funeral, and driving here and there..then the next weekend, another urgency occurs, and you don't get to the boat for what.. three weeks!
Well, my little bilge rat, if 5 minutes after he left his boat, the electric waterheater shorted out, simultaneously a micrometeoroid blazed out of the Great Ort Cloud and seemingly predestined, it falls to earth in your marina, striking a metal shed which then redirects it to your very own dock (wouldn't ya know it?), striking the power service box with a direct hit, knocking out the ground connection completely.
Now ya got trouble dude. And that switch is turned off..has been for weeks, so long in fact that the whole idea of flippin' that switch to test the light and the circuit, then switch the circuit off..but on again when you return to the boat..has been lost in the bussle of the days and weeks. ...and the electrons are merrily leaving your prop shaft, taking up new digs on other more noble bits and pieces in the area. So the switch, in my opinion is not worth the metal shavings to create the hole to mount it in.
If we start being concerned over third and fourth level possibilities, I think that there are some far more serious, and more likely to occur scenarios than this, to be worried about. Seems to me like this is a super-small risk with small consequences to boot, should a triple fault occur (we do not even consider this a possibility in computers..a double fault alone would cause two weeks of meetings!). Yet the Increased Danger to the people, from somone innocently repluugging their boats AC plug back in after they accidently knock it loose..but backwards (our dear captain had cut off the ground lug so that it could go in an old wall socket that had no ground) would cause me to speculate that this act could be, in fact illegal..no fooling~! There are codes for the grounding of vessels..at least two we have even talked of here. The same codes also call for a reverse polarity light and how it operates, and I will bet a bag of donut holes that they do require it to be installed, in circuit and working for the entire time that 120vac is used. I do not and have not seen this reference yet, but would be interested in reading it if anyone has per chance seen it?
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30
demers@sgi.com
I have our boat wired per the NFP codes, rather than the ABYC, which means that I do not have the green safety ground wired to my DC bonding or engine..only to devices that actually use 120vac, such as the inverter/charger. This connection in the charger is actually relay switched when it is in operation, so it is bonding the two grounds together when using the Inverter but not during charging. But I am not realy concerned here with bonding but the reverse polarity switches, and specificly Johns admonition about a series switch being needed.
I am relieved to hear that you read my long reply and understood what I was trying hard to say, and that you essentially agree with it. Now to your concern about the Electrolytic Current that the triple failure of A) Reversed Polarity between Line & Neutral B) Simultaneous failure of Ground at the Dock Service box and C) Simultaneously a 120vac device in the boat that is plugged in, turned on and fails with a short of the windings or one or either of Line and Neutral to a conductive area of the case, which is usually made of cheap plastic anyway, occurs. 120 ma of current will then certainly flow through the Rev. Polarity Lamp filament, and into ground, -water in this case, causing some mild electrlysis if alllowed to persist for months..or certainly weeks if this worsens an already electrolytic situation.
Your concern is one to be aware of. But guys, I have worked with statistical analysis for probably 20 years now, in determining likelyhood of a failure in a multi-milllion (transistors)gate array for our computers. The likelyhood of all of those things coming together and happening simultaneously is so very miniscule as to be a statistical zero. Additionally, an observant guy like you will certainly notice that the 120v device is not running nearly as fast as before, since the water is a poor ground, electrically. Wire is far, far better. So there will be the increased resistance to operate thru which drops the available voltage to the 120vac device, and which then operates the device much slower. It could also blow a 15Amp DC breaker (House Panel) on start up if it was an inductive load like a motor due to the voltage drop of water..especialy 1000's of feet of it to reach the shore ground rod. You will notice it if you are present when it operates.
So the problem should be self-evident if this mountain of bad luck befalls one. But the addition of a switch would certainly not relieve you of any of this so far..not a bit.
It would cut out that 120ma of current that would flow only during the time of this triple-whammy, this penultimate of accidents and random bad luck, all happening at once. No possibility of a rev. polarity light then...of course,
But the danger that you are being exposed to in exchange is far greater! Should that switch be left off accidently while the 120vac is in operation, you have given up your protection *from* Reversed Polarity events. This will then open you to possible lethal shock from simply touching the wrong 2 items on your boat..like holding on to your shrouds, while talking to the neighbor, who leans across to shake your hand..oh, he' s hanging onto his shrouds also!..Zap..two nice guys leave for the other side..and the lawyers line up in the aisles..
So if a guy were clever, he could combine a Rev.Polarity light test function with a spring return to center off, DPDT switch. Throw it one way, it lights the lamp for you assuring you that yes indeed it works now. Throw it the other, and the light will be taken out of the circuit totally until it is turned on manually.
Ahhh..see the problem with this thought?
Ok, so Joe Schmo decides he is going to prevent this dastardly "Stray" current from eating his beauty alive, so he throws the switch opening the circuit to the warning light, disabling it.
Suppose he forgets to check it one weekend, and low and behold grandpa Silly dies over the next weekend so there is the funeral, and driving here and there..then the next weekend, another urgency occurs, and you don't get to the boat for what.. three weeks!
Well, my little bilge rat, if 5 minutes after he left his boat, the electric waterheater shorted out, simultaneously a micrometeoroid blazed out of the Great Ort Cloud and seemingly predestined, it falls to earth in your marina, striking a metal shed which then redirects it to your very own dock (wouldn't ya know it?), striking the power service box with a direct hit, knocking out the ground connection completely.
Now ya got trouble dude. And that switch is turned off..has been for weeks, so long in fact that the whole idea of flippin' that switch to test the light and the circuit, then switch the circuit off..but on again when you return to the boat..has been lost in the bussle of the days and weeks. ...and the electrons are merrily leaving your prop shaft, taking up new digs on other more noble bits and pieces in the area. So the switch, in my opinion is not worth the metal shavings to create the hole to mount it in.
If we start being concerned over third and fourth level possibilities, I think that there are some far more serious, and more likely to occur scenarios than this, to be worried about. Seems to me like this is a super-small risk with small consequences to boot, should a triple fault occur (we do not even consider this a possibility in computers..a double fault alone would cause two weeks of meetings!). Yet the Increased Danger to the people, from somone innocently repluugging their boats AC plug back in after they accidently knock it loose..but backwards (our dear captain had cut off the ground lug so that it could go in an old wall socket that had no ground) would cause me to speculate that this act could be, in fact illegal..no fooling~! There are codes for the grounding of vessels..at least two we have even talked of here. The same codes also call for a reverse polarity light and how it operates, and I will bet a bag of donut holes that they do require it to be installed, in circuit and working for the entire time that 120vac is used. I do not and have not seen this reference yet, but would be interested in reading it if anyone has per chance seen it?
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30
Ken Coit wrote: Larry,
Again, a very thorough analysis; you are wonderful!
First of all, to the best of my knowledge, Parfait and other Cape Dorys do not employ the circuit I was discussing, so this is really an academic exercise to keep us from doing something less meaningful.
I was speculating with a hypothetical about two-bulb incadescent reverse polarity circuits where there will always be current flowing through one or the other of the bulbs. Since it is my hypothetical, I'll suggest that maybe 150 ma. is flowing all the time that AC is connected to the boat and the circuit is energized. Where it goes is the crux of the question. Without a reversal, it goes through the neutral lead and is no problem. With a reversal, the current goes through the neutral and safety ground and it can be a problem.
If the boat is wired per ABYC, with the safety AC ground (green) connected to the DC ground, and DC ground is connected to the water via thru-hulls, prop shaft, etc., then there is the possibility that if the safety ground is broken at the dockside and there is simultaneously a reversal of neutral and line, that the 150 ma. will try to flow through the water. If it does, it will cause problems somewhere.
To eliminate this failure mode, all one needs to do is to turn the reverse polarity circuit off when it isn't needed, like when you are not on board. That was my only point in suggesting that a switch be included in a two bulb incadescent reverse polarity circuit.
An alternative recommended by many, is to not leave the boat connected to the AC mains when you are not on board.
Thanks for your continuing thorough analyses.
Ken
Larry DeMers wrote: Ken,
You say there is "significant current flow all the time". WHere is the flow from? If the bulb is not lit, and it is a good bulb, that means that the bulb is not seeing a sufficient voltage differential to light the light, correct?
When the bulb is out, it means that the wires it is connected to are at the same or close to the same potential. In this case, that means that Ground and Neutral are the two lines in question now. They are properly tied together at the dock service box, so there should be no voltage between them, as *effectively* they are the same wire.
There is no current going into the underwater metal at this point.
Now say our boat owner has a bad day and rewires his boat one saturday, and accidently reverses Line (black) and Neutral (white). Now he goes down below and sees the "Polarity Reversed" Indicator is lit. Now that incandescent light will be across ground and line, sine the neutral and line were reversed. It will light..but if the ground is indeed intact, the current will be returning via the ground wire, not the water. There is no "Significant flow of electricity" in this case either.
Now say our boat owner has a really bad day, and somehow opens up ground and also reverses Line and Neutral. He walks down below, and notices that the "Reverse Polarity" light is lit. Now what is happeneing? Since the ground in this case, is open, and Line and Neutral are reversed too, the "Reverse Polarity light may or may not light at all..depends on where the Ground Fault happened. If it happened prior tot he point where ground and neutral were tied together, then the ground wire is floating in mid air..not connected to anything, and the Reverse polarity light will not light. Again, there is no "significant amount of current going into the water" in this case. In the example used here, the light IS lit, so the ground fault has to be after the Neutral to Ground tie in the dock service box. Now the return path for the "Rev. Polarity light" is the neutral wire, still connected. The light will light, and there is no significant electrolysis current flowing here either.
Remember that just because there is a parallel connection to the ships bonding system, current still takes the path of least resistance. Water is highly resistive compared to a copper cable in good shape, so the current will follow the cable as the return path, not the water. There is however, a very small portion of current that would flow in this case due to the water being a high resistance parallel path. It is not in the range ordinarily understood to cause electrlysis though. For this discussion, the parallel effect can be ignored, and the major path only considered. If you set up a condition where the return path is interrupted and you have a device using 120vac, it's return path could be thru the water, and that itself would be a consideration for possible electrolysis.
But to return to the Reverse Polarity Switch question, I do not see where there can be any current flow to the water in this circuit as designed, without the switch installed. I think the switch may be to actually provide a testing capability of that rev. polarity light..not activate it for testing.
If anyone can see what I am missing, please speak up and show me where you think the current is going and how. At this point, I am convinced that this topic was a bit of overreaction to start with, and escalated into a misunderstanding of how the grounds and rev.polarity circuit works.
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30 Lake Superior
Larry DeMers wrote:Ken Coit wrote: However, I suspect that part of the confusion is coming from other "Reverse Polarity" circuits that employ two indicators, one on the line and one on the neutral lines. These are usually arranged like the testers we find at the hardware store, with one red light and one green light, the intent being that green is good and any presence of red is bad whether with or without green. If the two indicator "Reverse Polarity" circuit is used with neon bulbs, it is still not a problem, but with incadescents, there is significant current flow all the time and there may well be significant electrolysis. I think in that case, I would like a switch to disconnect the "Reverse Polarity" circuit from safety ground, but I prefer the stock circuit found on CD/36s: one neon bulb which is normally across the neutral and safety ground lines with a momentary switch to connect the bulb to the hot line for testing the bulb. The pilot light is across the hot and neutral lines with no breakers between it and the pier; it is always on if we are on the grid.
Keep on sailing,
Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC
Ken Coit wrote:
demers@sgi.com
-
Larry DeMers
Re: Let's try again.......
John,
This exchange has gotten far from the point of interest, I expect, so lets stop here. I think you have confused two issues; namely the installation of a serial switch in the Reverse Polarity Indicators path, which you certainly did champion and the discussion has in fact originated this whole thread. ..and, ground bonding of the boat, which was not the original discussion.
My position on this, one which you apparently do agree with if I understand what you said, is that the switch in the rev. polarity circuit is not needed in normal circumstances. There will be NO current flow..there can be none.
Electrolysis causinng current can flow ONLY when there is a triple failure of the power service at the dock..ie: ground is opened, Line and Neutral are reversed simulaneously..*and* there is a failure of an operating 120vac device's insulation between ground and either of Line or Neutral. Then it wil be limited to the resistance of the filament resistance, or about 120ma. of current. This is very mild for electrlytic current, but should be stopped of ocurse. It will not eat up your boat overnight..but the zincs may be pinker for it if this goes on for weeks etc.
The other side fo the coin of course, is the Very Significant Danger you put your own self and crew to, when you operate your vessel without a working reverse polarity lamp..remember, we turned it off last month and forgot it?? here, the donwside of a Rev. Pol. failure is death from electrocution..not a pleasant way to go at all.
So it seems foolish to think that we should interrupt a possible life saving signal, for the very remotest of possibilities that there would ever be a triple-failure event that could cause the filament path of the Rev. Pol. lamp to conduct sufficient current into the water to cause electrlysis. The two are just of different priorities, I guess. Life over electrolysis paranoia.
lastly, there is a great chance that what you are suggesting may be against the codes, (or at least immoral)heh. This is an action that has health consequences if carried out, so it would make sense that there would be some rule against it.
Enough..on to sailing! We launch this weekend, finally.
Cheers,
Larry Demers
s/v DeLaMer
Guys,
This is getting really messed up with too much verbage, and so I would like to end it here with this
demers@sgi.com
This exchange has gotten far from the point of interest, I expect, so lets stop here. I think you have confused two issues; namely the installation of a serial switch in the Reverse Polarity Indicators path, which you certainly did champion and the discussion has in fact originated this whole thread. ..and, ground bonding of the boat, which was not the original discussion.
My position on this, one which you apparently do agree with if I understand what you said, is that the switch in the rev. polarity circuit is not needed in normal circumstances. There will be NO current flow..there can be none.
Electrolysis causinng current can flow ONLY when there is a triple failure of the power service at the dock..ie: ground is opened, Line and Neutral are reversed simulaneously..*and* there is a failure of an operating 120vac device's insulation between ground and either of Line or Neutral. Then it wil be limited to the resistance of the filament resistance, or about 120ma. of current. This is very mild for electrlytic current, but should be stopped of ocurse. It will not eat up your boat overnight..but the zincs may be pinker for it if this goes on for weeks etc.
The other side fo the coin of course, is the Very Significant Danger you put your own self and crew to, when you operate your vessel without a working reverse polarity lamp..remember, we turned it off last month and forgot it?? here, the donwside of a Rev. Pol. failure is death from electrocution..not a pleasant way to go at all.
So it seems foolish to think that we should interrupt a possible life saving signal, for the very remotest of possibilities that there would ever be a triple-failure event that could cause the filament path of the Rev. Pol. lamp to conduct sufficient current into the water to cause electrlysis. The two are just of different priorities, I guess. Life over electrolysis paranoia.
lastly, there is a great chance that what you are suggesting may be against the codes, (or at least immoral)heh. This is an action that has health consequences if carried out, so it would make sense that there would be some rule against it.
Enough..on to sailing! We launch this weekend, finally.
Cheers,
Larry Demers
s/v DeLaMer
Guys,
This is getting really messed up with too much verbage, and so I would like to end it here with this
John R. wrote: There is a little more detail to the story please see retort comments below, I certainly hope matters are clarified:
Larry: : Hi Everyone,
John: Good observation but not always true, there is the *other* "condition". Some panels may be fine and some not. I never ever said all CD panels need the momentary switch, if memory serves I indicated that owners should check their panels and see if it was necessary. Like I said in a previous post to you the AC return current is the problem. I should at this time make perfectly clear that if the boat does not have an ABYC recommended vessel safety ground then it would not be necessary because the neutral and safety ground return to shore. Some CD's have this and some do not. If a boat is wired in accordance with ABYC electrical standards (which some CD AC services are not)and has an AC safety ground to the vessels common ground point then there is a stray current problem if the vessel is using an incandescent reverse polarity lamp.Larry DeMers wrote: I was thinking about the warning that John R. gave us about the reverse polarity light needing a switch to break a "stray current path" that could result in increased current pressure on the bonded parts of the boat, which might increase your electrolysis potential, and have come to a point where I doubt that this is true under all but one circumstance.
This warning that JohnR gave us would be valid IF you lost both the Neutral AND Ground lines to the service terminal on the dock. Under no other condition can I see where *any* current can flow thru the reverse polarity light to ground or neutral (essentially these two are tied together at the dock, so they are and should be the same). This means that the panels you have without the switch are fine.
Larry: Here is the description of how this circuit operates and why it cannot be a source of "stray current" electrolysis under normal conditions:
John: YES, including the AC power indicator light (a device)!Larry DeMers wrote: You have 3 wires coming in to your boat; Line (which is the hot wire), Neutral (which is the return path for any 120vac used by a device onboard)
You just revealed the potential problem.
Larry: This Reverse Polarity light is connected between the Neutral and Green Wire Grounds of the incoming 120vac service cable. In normal conditions..ie: no faults, there is and can be *no* voltage impressed across this lamp, therefore no current flows, and there can be NO stray current issue here, since it is essentially a dead circuit.
John: The *power indicator light* has one hot leg and one neutral leg, power comes in on the hot leg. The neutral leg of that indicator lamp (which carries returning current) connects to the *line terminal* of the neutral circuit breaker along with one leg of the reverse polarity indicator light (This is the problem). The other leg of the reverse polarity light goes to ground.
When a boat has a onboard AC safety ground (green wire)to the boats common ground point (engine , dynaplate etc) then returning current from the power indicator light will follow the neutral and ground to all points of ground. That means it can go back to shore via the ground or neutral or can go to the water (or via all three)and does cause stray current problems when current enters the water. This is based on a boat wired to ABYC standards.
Now at this point some will say there is an easy solution, just disconnect or don't have an on board AC safety ground circuit that doesn't return to shore only. I suppose that would be okay if you totally trusted the integrity of every ground connection at every marina and shore side hook up. In my eyes (an evidently ABYC's) that is being naive and careless. If a short occurs on board in any AC appliance including the boat inlet components, transfer switches, etc then you could quite frankly be electrocuted if there is not a safety ground that has full integrity to handle a short. That is why ABYC guidelines stipulate a onboard AC safety ground be wired to a vessels common ground point. Now, having said that...by doing this you then open the opportunity for the reverse polarity light stray current entering the water (the returning power indicator current). A momentary switch installed between the reverse polarity indicator light and the ground prevents that stray current scenario.
Furthermore for those who don't like the AC ground standards that ABYC advocates and do not want to incorporate their electrical recommendations just keep in mind if you run a generator set or an AC inverter on board you basically have no safety ground on your AC distribution system because you are no longer hooked to a shoreside connection.
Larry: There the Rev. Polarity lamp will light is if there is a voltage difference between it's two leads, which then means that there will be a current flow from one lead, thru the filament of the lamp to the other lead.
John: Only in the case of a boat that does not meet ABYC electrical standards.Larry DeMers wrote: So for the lamp to light in our boats, we have to have a situation where there is a voltage difference between neutral and ground. Remember that these two wires started out shorted together back on the dock, right?
The condition that will cause this to happen is where Line (the hot wire) and the Neutral (return) wire were swapped at the dock or in the boats 120vac wiring. Here, the lamp WILL see Line voltage (hot) on one filament lead instead of Neutral (essentially ground). The other lamp lead remains connected to Ground. Now we have a voltage difference between the two leads..120v of difference, and the lamp will light.
These are the only situations where the lamp should lite I believe.
Now for "stray current" electrolysis to happen, the Neutral and the ground connections to shore must be open, and you must have a reversed polarity situation on the cable also. That is a three point failure in the 120vac service to your boat, and it probably would not happen in 5 lifetimes! Even if it did, you would certainly be aware of it, as the 120vac would not work properly, since the return path would be thru the boats underwater bonding and metal fittings to shore ground rod..a very long way aways from the boat usually, so that means resistance, which means the voltage would be far less than 120vac at your appliance, and it would not work like normal. SO you would be aware of something wrong. The reverse polarity light would also be on, and here is where John is correct. The current thru the light, about 120ma, would run thru the bonding system to the underwater features on your boat, to the shore ground rod.
**That will cause some electrolysis for the time that the reverse polarity light is on only.**
So to get to this position of electrolysis, we need a triple failure of the 120vac system onboard or at the dock. the damage would only occur while the reverse polarity light was actually on.
Larry: This, by the way, *is not* stray current, but rather direct AC current. There IS no stray current possible in any configuration of this circuit.
John: In your scenario Larry that is true but in the scenario I have outlined that is not the case because the power indicator is always illuminated when hooked to shore in a typical AC distribution panel installation.
It is stray current.
Larry: Stray current is current that flows even when the circuit is turned off, and that clearly would be impossible in this circuit since under normal circumstances, the lamps two leads are connected to essentially the same wire (as the Neutral and Ground wires are -once again, shorted together at the service terminal on the dock).
John: And Cheers to you Larry.
I hope this stuff is all clarified. I have a feeling many folks are probably pretty darned confused by now. It is so simple to illustrate but difficult to discuss.
Please note: If memory serves some CD owners manuals will show an AC circuit schematic but probably will not indicate an onboard AC safety ground except the one afforded by the shore side cable. Therein is where the safety and stray current issues arise. The CD schematic I'm familiar with does not meet ABYC (American Boat and Yacht Council) standards.
If someone notes errors in my or Larrys comments please point them out.
Larry DeMers wrote: Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30
Lake Superior
Randy Bates wrote: Should the AC indicator light come on as soon as the shore power cord is connected or does the main CB need to be switched on?
Is the "AC reversed" light function active as soon as shore power is connected? IE, if NOT reversed, NO light. Is the switch associated with the "AC Reversed" light a test switch for the light NOT for a reversed AC condition?
demers@sgi.com
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Ken Coit
ROFL - Thanks; ABYC quoted by Casey
Larry,
Thanks for a very humourous treatise. After all we have said about this, I like my stock Cape Dory solution: one neon bulb across the mains to indicate that AC is connected to the boat and another across neutral and safety ground that tells me if there is a "polarity reversal," with a momentary switch for testing the bulb. I think they did it right.
Quoting from "Sailboat Electrics Simplified" by Don Casey, "The ABYC recommends reverse polarity indicators on all AC main panels. It also suggests that that the resistance of such indicators be at least 25,000 ohms in order that they not bypass any isolation transformer or galvanic isolation devices installed in the shore power circuit."
The home project circuit Casey shows on page 288 uses two 120 VAC neons, one red and one green, and two current limiting resistors of 35K ohms each. There are no switches.
I like having my batteries floating on the charger, but I am begining to wonder...
Ken
parfaitNOSPAM@nc.rr.com
Thanks for a very humourous treatise. After all we have said about this, I like my stock Cape Dory solution: one neon bulb across the mains to indicate that AC is connected to the boat and another across neutral and safety ground that tells me if there is a "polarity reversal," with a momentary switch for testing the bulb. I think they did it right.
Quoting from "Sailboat Electrics Simplified" by Don Casey, "The ABYC recommends reverse polarity indicators on all AC main panels. It also suggests that that the resistance of such indicators be at least 25,000 ohms in order that they not bypass any isolation transformer or galvanic isolation devices installed in the shore power circuit."
The home project circuit Casey shows on page 288 uses two 120 VAC neons, one red and one green, and two current limiting resistors of 35K ohms each. There are no switches.
I like having my batteries floating on the charger, but I am begining to wonder...
Ken
parfaitNOSPAM@nc.rr.com
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Larry DeMers
Re: ROFL - Thanks; ABYC quoted by Casey
Ken,
Floating the batteries on the charger is just fine if the system is wired as you have said, the battery charger is a 3 stage device, so that this time on charge will be the float stage, and not some other charge level. I leave our power on continually..for many reasons. But I do agree with you and with JohnR that the one possible problem of the rev. pol. lamp letting a tad of current thru may be a valid reason to replace the bulbs with neon bulbs. Especially if it worries you..replace them. However, I also now see that knowing the condition of that bulb is even more important, so I am adding a test switch to that panel..this weekend (after launching Friday).
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30
demers@sgi.com
Floating the batteries on the charger is just fine if the system is wired as you have said, the battery charger is a 3 stage device, so that this time on charge will be the float stage, and not some other charge level. I leave our power on continually..for many reasons. But I do agree with you and with JohnR that the one possible problem of the rev. pol. lamp letting a tad of current thru may be a valid reason to replace the bulbs with neon bulbs. Especially if it worries you..replace them. However, I also now see that knowing the condition of that bulb is even more important, so I am adding a test switch to that panel..this weekend (after launching Friday).
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30
Ken Coit wrote: Larry,
Thanks for a very humourous treatise. After all we have said about this, I like my stock Cape Dory solution: one neon bulb across the mains to indicate that AC is connected to the boat and another across neutral and safety ground that tells me if there is a "polarity reversal," with a momentary switch for testing the bulb. I think they did it right.
Quoting from "Sailboat Electrics Simplified" by Don Casey, "The ABYC recommends reverse polarity indicators on all AC main panels. It also suggests that that the resistance of such indicators be at least 25,000 ohms in order that they not bypass any isolation transformer or galvanic isolation devices installed in the shore power circuit."
The home project circuit Casey shows on page 288 uses two 120 VAC neons, one red and one green, and two current limiting resistors of 35K ohms each. There are no switches.
I like having my batteries floating on the charger, but I am begining to wonder...
Ken
demers@sgi.com
-
Ken Coit
Yes - Neons fail
Larry,
Yes, even neons fail if they are left on contiuously; you do need to be able to test them since they are hard wired, at least on Parfait. I think they are usually spec'd at 20-25K hours life, so after a couple of years or so, one can expect to have to replace them if the boat is on the grid all the time, save the minor sailings.
I was surprised to find spare pilot lamps on board Parfait; I guess it had failed before, maybe often. The indicator had certainly become rather intermittant over the past 2 years.
Have a great launch!
Ken
parfaitNOSPAM@nc.rr.com
Yes, even neons fail if they are left on contiuously; you do need to be able to test them since they are hard wired, at least on Parfait. I think they are usually spec'd at 20-25K hours life, so after a couple of years or so, one can expect to have to replace them if the boat is on the grid all the time, save the minor sailings.
I was surprised to find spare pilot lamps on board Parfait; I guess it had failed before, maybe often. The indicator had certainly become rather intermittant over the past 2 years.
Have a great launch!
Ken
Larry DeMers wrote: Ken,
Floating the batteries on the charger is just fine if the system is wired as you have said, the battery charger is a 3 stage device, so that this time on charge will be the float stage, and not some other charge level. I leave our power on continually..for many reasons. But I do agree with you and with JohnR that the one possible problem of the rev. pol. lamp letting a tad of current thru may be a valid reason to replace the bulbs with neon bulbs. Especially if it worries you..replace them. However, I also now see that knowing the condition of that bulb is even more important, so I am adding a test switch to that panel..this weekend (after launching Friday).
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30
Ken Coit wrote: Larry,
Thanks for a very humourous treatise. After all we have said about this, I like my stock Cape Dory solution: one neon bulb across the mains to indicate that AC is connected to the boat and another across neutral and safety ground that tells me if there is a "polarity reversal," with a momentary switch for testing the bulb. I think they did it right.
Quoting from "Sailboat Electrics Simplified" by Don Casey, "The ABYC recommends reverse polarity indicators on all AC main panels. It also suggests that that the resistance of such indicators be at least 25,000 ohms in order that they not bypass any isolation transformer or galvanic isolation devices installed in the shore power circuit."
The home project circuit Casey shows on page 288 uses two 120 VAC neons, one red and one green, and two current limiting resistors of 35K ohms each. There are no switches.
I like having my batteries floating on the charger, but I am begining to wonder...
Ken
parfaitNOSPAM@nc.rr.com
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John R.
Re: Let's try again.......
John R says:Larry DeMers wrote: John,
This exchange has gotten far from the point of interest, I expect, so lets stop here.
Sure Larry, I agree after I have the same opportunity you just had in defending my valid point of view for a final time.
Larry says:
I think you have confused two issues; namely the installation of a serial switch in the Reverse Polarity Indicators path, which you certainly did champion and the discussion has in fact originated this whole thread. ..and, ground bonding of the boat, which was not the original discussion.
John R says:
No sir, I haven't confused anything at all. Please do not imply that which is not correct. I do not and have not accused you of being "confused" even though my factual remarks have been reviewed from one scenario only, your adament opinion. Although I disagree with the AC wiring you use Larry that does not stop me from acknowledging when your remarks are in line, which I have done, I have never implied your scenario was wrong in your described case. My practice and viewpoint is in conflict with the AC wiring you utilize on your boat and so I defend the ABYC AC wiring standard that I endorse. I acknowledge your non-use of a momentary switch in your boats non-ABYC code AC electrical system, I've never argued it.
One last time for others........The momentary switch referenced by me IS necessary in a boat meeting ABYC AC wiring standards and utilizing an incandescent bulb as the vessel polarity light. Fact.....*** some Cape Dories meet this criteria ***. Therefore, they are susceptible to stray current as I explained clearly and simply before. It is for owners of those vessels that I make my comments.
You do not fit that profile with the way you have your boat wired Larry. As you freely admit your boat does not meet ABYC AC electrical standards and so does not need the momentary switch. That is your choice. Sir, many people are not in your situation and my original post recommendation may apply to them and their wiring if it meets ABYC code and standards. Thus I had advised them to check their panels and distribution system. I can't say it any clearer than that. It should not be labeled as wrong just because the practice does not apply to YOUR situation.
Please allow me my peace in presenting the issue. It is a perfectly valid and factual point in my original post, just different than your system. People can apply the facts to their individual wiring situation. You explained your system and I have explained mine and ABYC's. I believe I have understood your remarks correctly. We differ from you, that does not make us wrong at all, an impression I get from your writings that you imply. Certainly we are not.
Larry says:
John R says:Larry DeMers wrote: My position on this, one which you apparently do agree with if I understand what you said, is that the switch in the rev. polarity circuit is not needed in normal circumstances. There will be NO current flow..there can be none.
Which "normal", your normal or ABYC's normal? I agree with you as I previously indicated that the switch is not necessary in your method of wiring the AC system.
I absolutely do not agree with you if a boat is wired to ABYC electrical standards which I emphatically advocate every boat owner concerned with proper ABYC wiring adhere to.
Larry says:
John R says:Larry DeMers wrote: Electrolysis causinng current can flow ONLY when there is a triple failure of the power service at the dock..ie: ground is opened, Line and Neutral are reversed simulaneously..*and* there is a failure of an operating 120vac device's insulation between ground and either of Line or Neutral. Then it wil be limited to the resistance of the filament resistance, or about 120ma. of current. This is very mild for electrlytic current, but should be stopped of ocurse. It will not eat up your boat overnight..but the zincs may be pinker for it if this goes on for weeks etc.
120 milliamps as you put it is nonetheless 120 milliamps that should not be there regardless of how long it takes to do the damage.... an hour, a day, a week, or a month or more. Pinkish is dezincified and that is degraded integrity of the part which is a problem. In the marine business this would not be acceptable by any means. An owner should be concerned about any and all stray current. This is especially true for a person entrusted with eliminating stray current such as a mechanic or electrical specialist. Slow or fast, it isn't a flippant matter.
Larry says:
John R says:Larry DeMers wrote: The other side fo the coin of course, is the Very Significant Danger you put your own self and crew to, when you operate your vessel without a working reverse polarity lamp..remember, we turned it off last month and forgot it?? here, the donwside of a Rev. Pol. failure is death from electrocution..not a pleasant way to go at all.
A polarity failure is definitely a serious danger, and yet the wiring system you advocate is not a danger when it doesn't have a onboard AC safety ground leading to water (ABYC wiring code).......not hardly. You are putting your life in the in the hands of the integrity of the ground connection (a mere screw connection for example that is probably never maintained)at the local marina or wherever a person hooks up shorepower.
Any prudent owner/skipper who would utilize the momentary switch as outlined would certainly be wise enough to always press the momentary switch to check for a reverse polarity condition immediately after plugging into any shorepower connection. The lamp integrity can easily be tested periodically or a lamp test switch can be incorporated into the panel.
Larry says:
John R. says:Larry DeMers wrote: So it seems foolish to think that we should interrupt a possible life saving signal, for the very remotest of possibilities that there would ever be a triple-failure event that could cause the filament path of the Rev. Pol. lamp to conduct sufficient current into the water to cause electrlysis.
I never said that at all (triple failure event in your system), Once again this is your system not an ABYC system. Reread my comments carefully from day one.
Larry says:
The two are just of different priorities, I guess. Life over electrolysis paranoia.: lastly, there is a great chance that what you are suggesting may be against the codes, (or at least immoral)heh. This is an action that has health consequences if carried out, so it would make sense that there would be some rule against it.
John R says:
No, in fact my recommendation is totally in line with ABYC standards/codes for AC wiring, period. Perhaps to some people stray current concerns may be worrisome but can easily be dealt with. I (and ABYC) feel it is far better to live with that than be living dangerously without a safety ground to water aboard a vessel.
To each his own.
The end.
Have a good day.
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John R.
Re: Yes - Neons fail
Hurray......We all totally agree on something. The R.P. indicator lamp should be tested on a regular basis.
Ken Coit wrote: Larry,
Yes, even neons fail if they are left on contiuously; you do need to be able to test them since they are hard wired, at least on Parfait. I think they are usually spec'd at 20-25K hours life, so after a couple of years or so, one can expect to have to replace them if the boat is on the grid all the time, save the minor sailings.
I was surprised to find spare pilot lamps on board Parfait; I guess it had failed before, maybe often. The indicator had certainly become rather intermittant over the past 2 years.
Have a great launch!
Ken
Larry DeMers wrote: Ken,
Floating the batteries on the charger is just fine if the system is wired as you have said, the battery charger is a 3 stage device, so that this time on charge will be the float stage, and not some other charge level. I leave our power on continually..for many reasons. But I do agree with you and with JohnR that the one possible problem of the rev. pol. lamp letting a tad of current thru may be a valid reason to replace the bulbs with neon bulbs. Especially if it worries you..replace them. However, I also now see that knowing the condition of that bulb is even more important, so I am adding a test switch to that panel..this weekend (after launching Friday).
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30
Ken Coit wrote: Larry,
Thanks for a very humourous treatise. After all we have said about this, I like my stock Cape Dory solution: one neon bulb across the mains to indicate that AC is connected to the boat and another across neutral and safety ground that tells me if there is a "polarity reversal," with a momentary switch for testing the bulb. I think they did it right.
Quoting from "Sailboat Electrics Simplified" by Don Casey, "The ABYC recommends reverse polarity indicators on all AC main panels. It also suggests that that the resistance of such indicators be at least 25,000 ohms in order that they not bypass any isolation transformer or galvanic isolation devices installed in the shore power circuit."
The home project circuit Casey shows on page 288 uses two 120 VAC neons, one red and one green, and two current limiting resistors of 35K ohms each. There are no switches.
I like having my batteries floating on the charger, but I am begining to wonder...
Ken
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John R.
Re: ROFL - Thanks; ABYC quoted by Casey
Very good post Ken. Casey is on the mark paraphrasing ABYC. A 25k resistor or such would be just as good as a momentary switch or neon light. Anything that prevents the current from entering an AC safety ground (green)that goes to the boats common ground point, vessel ground (I underscore that). Thing is at this point I don't know which of these components would be the most dependable choice because I'm not an electronics component expert.
I said in another post that was my last word on this topic but then I read your post. Sorry I broke my word.
I said in another post that was my last word on this topic but then I read your post. Sorry I broke my word.
Ken Coit wrote: Larry,
Thanks for a very humourous treatise. After all we have said about this, I like my stock Cape Dory solution: one neon bulb across the mains to indicate that AC is connected to the boat and another across neutral and safety ground that tells me if there is a "polarity reversal," with a momentary switch for testing the bulb. I think they did it right.
Quoting from "Sailboat Electrics Simplified" by Don Casey, "The ABYC recommends reverse polarity indicators on all AC main panels. It also suggests that that the resistance of such indicators be at least 25,000 ohms in order that they not bypass any isolation transformer or galvanic isolation devices installed in the shore power circuit."
The home project circuit Casey shows on page 288 uses two 120 VAC neons, one red and one green, and two current limiting resistors of 35K ohms each. There are no switches.
I like having my batteries floating on the charger, but I am begining to wonder...
Ken
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Ken Coit
Re: ROFL - Thanks; ABYC quoted by Casey
John,
You are forgiven!
The resistor is needed to limit the current through the neon bulb, it would not be practical to add it to an incadescent circuit because the light would never turn on.
Because the reverse polarity lamp is going to cause current to flow in the safety ground if the polarity is reversed, I think a neon or other very low current indicator is much to be desired to minimize safety and electolysis hazzards. A switch will do that as well, but then we may forget to turn the switch on creating another potential hazzard.
Thanks for the in-depth discussion.
Keep on sailing,
Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC
parfaitNOSPAM@nc.rr.com
You are forgiven!
The resistor is needed to limit the current through the neon bulb, it would not be practical to add it to an incadescent circuit because the light would never turn on.
Because the reverse polarity lamp is going to cause current to flow in the safety ground if the polarity is reversed, I think a neon or other very low current indicator is much to be desired to minimize safety and electolysis hazzards. A switch will do that as well, but then we may forget to turn the switch on creating another potential hazzard.
Thanks for the in-depth discussion.
Keep on sailing,
Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC
John R. wrote: Very good post Ken. Casey is on the mark paraphrasing ABYC. A 25k resistor or such would be just as good as a momentary switch or neon light. Anything that prevents the current from entering an AC safety ground (green)that goes to the boats common ground point, vessel ground (I underscore that). Thing is at this point I don't know which of these components would be the most dependable choice because I'm not an electronics component expert.
I said in another post that was my last word on this topic but then I read your post. Sorry I broke my word.
Ken Coit wrote: Larry,
Thanks for a very humourous treatise. After all we have said about this, I like my stock Cape Dory solution: one neon bulb across the mains to indicate that AC is connected to the boat and another across neutral and safety ground that tells me if there is a "polarity reversal," with a momentary switch for testing the bulb. I think they did it right.
Quoting from "Sailboat Electrics Simplified" by Don Casey, "The ABYC recommends reverse polarity indicators on all AC main panels. It also suggests that that the resistance of such indicators be at least 25,000 ohms in order that they not bypass any isolation transformer or galvanic isolation devices installed in the shore power circuit."
The home project circuit Casey shows on page 288 uses two 120 VAC neons, one red and one green, and two current limiting resistors of 35K ohms each. There are no switches.
I like having my batteries floating on the charger, but I am begining to wonder...
Ken
parfaitNOSPAM@nc.rr.com
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John R.
Re: ROFL - Thanks; ABYC quoted by Casey
Thanks for not holding me to my own restriction!
You know I believe a neon indicator already has a resistor inside it which lowers the 120V to around 90V max I think. You wouldn't need an external one. We'll have to check on that. You do note the one drawback of a switch as did Larry but that is where the owner/skipper comes in just like in other matters. I was thinking this afternoon that perhaps a LED would be the best choice. I think their life span would be infinite and you would need the resistor anyway. Starts to sound even better than going neon.
You know I believe a neon indicator already has a resistor inside it which lowers the 120V to around 90V max I think. You wouldn't need an external one. We'll have to check on that. You do note the one drawback of a switch as did Larry but that is where the owner/skipper comes in just like in other matters. I was thinking this afternoon that perhaps a LED would be the best choice. I think their life span would be infinite and you would need the resistor anyway. Starts to sound even better than going neon.
Ken Coit wrote: John,
You are forgiven!
The resistor is needed to limit the current through the neon bulb, it would not be practical to add it to an incadescent circuit because the light would never turn on.
Because the reverse polarity lamp is going to cause current to flow in the safety ground if the polarity is reversed, I think a neon or other very low current indicator is much to be desired to minimize safety and electolysis hazzards. A switch will do that as well, but then we may forget to turn the switch on creating another potential hazzard.
Thanks for the in-depth discussion.
Keep on sailing,
Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC
John R. wrote: Very good post Ken. Casey is on the mark paraphrasing ABYC. A 25k resistor or such would be just as good as a momentary switch or neon light. Anything that prevents the current from entering an AC safety ground (green)that goes to the boats common ground point, vessel ground (I underscore that). Thing is at this point I don't know which of these components would be the most dependable choice because I'm not an electronics component expert.
I said in another post that was my last word on this topic but then I read your post. Sorry I broke my word.
Ken Coit wrote: Larry,
Thanks for a very humourous treatise. After all we have said about this, I like my stock Cape Dory solution: one neon bulb across the mains to indicate that AC is connected to the boat and another across neutral and safety ground that tells me if there is a "polarity reversal," with a momentary switch for testing the bulb. I think they did it right.
Quoting from "Sailboat Electrics Simplified" by Don Casey, "The ABYC recommends reverse polarity indicators on all AC main panels. It also suggests that that the resistance of such indicators be at least 25,000 ohms in order that they not bypass any isolation transformer or galvanic isolation devices installed in the shore power circuit."
The home project circuit Casey shows on page 288 uses two 120 VAC neons, one red and one green, and two current limiting resistors of 35K ohms each. There are no switches.
I like having my batteries floating on the charger, but I am begining to wonder...
Ken
-
Ken Coit
Re: ROFL - Thanks; ABYC quoted by Casey
John,
Neon indicator assemblies probably all contain resistors, but you can buy bulbs separately and these need to have a resistor in the circuit. The resistor limits the current through the circuit and the voltage on the bulb but only when it is operational. At 5 ma. a 35K ohm resistor would drop the voltage by 175 volts, so we won't be getting 5 ma. through that 117 VAC circuit; at 5 ma and 25K ohm, the drop would be 125 volts; at 4 ma. and 25k ohm, the drop would be 100 volts. However, if no current is flowing, the bulb has full voltage across it.
I am becoming more of a fan of LED indicator lamps for their low current drain, high visibility, and color selection. I await higher levels of production which will make them more affordable. GE seems to be headed in that direction with fairly large white LED assemblies to replace incadescent light bulbs.
Thanks for plugging on trying to keep us safe and our boats afloat.
Ken
parfaitNOSPAM@nc.rr.com
Neon indicator assemblies probably all contain resistors, but you can buy bulbs separately and these need to have a resistor in the circuit. The resistor limits the current through the circuit and the voltage on the bulb but only when it is operational. At 5 ma. a 35K ohm resistor would drop the voltage by 175 volts, so we won't be getting 5 ma. through that 117 VAC circuit; at 5 ma and 25K ohm, the drop would be 125 volts; at 4 ma. and 25k ohm, the drop would be 100 volts. However, if no current is flowing, the bulb has full voltage across it.
I am becoming more of a fan of LED indicator lamps for their low current drain, high visibility, and color selection. I await higher levels of production which will make them more affordable. GE seems to be headed in that direction with fairly large white LED assemblies to replace incadescent light bulbs.
Thanks for plugging on trying to keep us safe and our boats afloat.
Ken
John R. wrote: Thanks for not holding me to my own restriction!
You know I believe a neon indicator already has a resistor inside it which lowers the 120V to around 90V max I think. You wouldn't need an external one. We'll have to check on that. You do note the one drawback of a switch as did Larry but that is where the owner/skipper comes in just like in other matters. I was thinking this afternoon that perhaps a LED would be the best choice. I think their life span would be infinite and you would need the resistor anyway. Starts to sound even better than going neon.
Ken Coit wrote: John,
You are forgiven!
The resistor is needed to limit the current through the neon bulb, it would not be practical to add it to an incadescent circuit because the light would never turn on.
Because the reverse polarity lamp is going to cause current to flow in the safety ground if the polarity is reversed, I think a neon or other very low current indicator is much to be desired to minimize safety and electolysis hazzards. A switch will do that as well, but then we may forget to turn the switch on creating another potential hazzard.
Thanks for the in-depth discussion.
Keep on sailing,
Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC
Ken Coit wrote:John R. wrote: Very good post Ken. Casey is on the mark paraphrasing ABYC. A 25k resistor or such would be just as good as a momentary switch or neon light. Anything that prevents the current from entering an AC safety ground (green)that goes to the boats common ground point, vessel ground (I underscore that). Thing is at this point I don't know which of these components would be the most dependable choice because I'm not an electronics component expert.
I said in another post that was my last word on this topic but then I read your post. Sorry I broke my word.
parfaitNOSPAM@nc.rr.com