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?
randy.bates@baesystems.com
CD25D AC Panel
Moderator: Jim Walsh
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Bill
Re: CD25D AC Panel
Randy
That is the way mine works (green light on, switch off)....but it is just a power shore switch, no distribution panel....The red light comes on only if there is a polarity switch. (I think polarity is the correct word)
Bill
cd25d@rhapsodysails.com
That is the way mine works (green light on, switch off)....but it is just a power shore switch, no distribution panel....The red light comes on only if there is a polarity switch. (I think polarity is the correct word)
Bill
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?
cd25d@rhapsodysails.com
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Ken Coit
Re: CD25D AC Panel
Randy,
Parfait has an AC pilot light that is on if shore power is connected, regardless of the position of the breakers. She also has a "reverse polarity" light that comes on if the polarity is wrong (hot and neutral are reversed somewhere); the lamp can be tested by throwing the switch, temporarily connecting the lamp across the hot and safety ground leads. Both of these are wired per the CD/36 manual.
Keep on sailing,
Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC
parfaitNOSPAM@nc.rr.com
Parfait has an AC pilot light that is on if shore power is connected, regardless of the position of the breakers. She also has a "reverse polarity" light that comes on if the polarity is wrong (hot and neutral are reversed somewhere); the lamp can be tested by throwing the switch, temporarily connecting the lamp across the hot and safety ground leads. Both of these are wired per the CD/36 manual.
Keep on sailing,
Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC
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?
parfaitNOSPAM@nc.rr.com
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Randy Bates
Re: CD25D AC Panel
Thanks guys. I was real concerned when the "AC reversed" light came on when I toggled the switch. The CD25D manual is not too clear.Bill wrote: Randy
That is the way mine works (green light on, switch off)....but it is just a power shore switch, no distribution panel....The red light comes on only if there is a polarity switch. (I think polarity is the correct word)
Bill
randy.bates@baesystems.com
-
Bill
Re: CD25D AC Panel
Randy
Please explain something!!! Does you "AC Reversed" light mean "reversed polarity"????? If I understand things correctly...you are turning on the shore power switch and the red light comes on. Is that correct???? IF so then you have a problem with your shore power, probably at the meter!!!! and it could damage AC "appliances" on board!!! I am not an electrician, but someone else will respond I am sure.
Please clarify your statement.
Bill
cd25d@rhapsodysails.com
Please explain something!!! Does you "AC Reversed" light mean "reversed polarity"????? If I understand things correctly...you are turning on the shore power switch and the red light comes on. Is that correct???? IF so then you have a problem with your shore power, probably at the meter!!!! and it could damage AC "appliances" on board!!! I am not an electrician, but someone else will respond I am sure.
Please clarify your statement.
Bill
Randy Bates wrote:Thanks guys. I was real concerned when the "AC reversed" light came on when I toggled the switch. The CD25D manual is not too clear.Bill wrote: Randy
That is the way mine works (green light on, switch off)....but it is just a power shore switch, no distribution panel....The red light comes on only if there is a polarity switch. (I think polarity is the correct word)
Bill
cd25d@rhapsodysails.com
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randy Bates
Re: CD25D AC Panel
NO. The light ONLY comes on when the switch that is beside it is toggled, not the AC breaker switch. The AC monitor light comes on as SOON as AC is connected regardless of the position of the breaker. Makes sense to me. The switch beside the "AC Reversed" allows for testing of the "AC Reversed" light. Otherwise you'd never know if the lamp was burned out. The other AC light is "ON" as soon as AC is connected in-order to alert you to the fact that AC is connected to the boat, not to tell you if you'd flipped a switch. Does this make sense to you. Bottom line--Connect AC, get red panel light, NOT "AC reversed light".
randy.bates@baesystems.com
Bill wrote: Randy
Please explain something!!! Does you "AC Reversed" light mean "reversed polarity"????? If I understand things correctly...you are turning on the shore power switch and the red light comes on. Is that correct???? IF so then you have a problem with your shore power, probably at the meter!!!! and it could damage AC "appliances" on board!!! I am not an electrician, but someone else will respond I am sure.
Please clarify your statement.
Bill
Randy Bates wrote:Thanks guys. I was real concerned when the "AC reversed" light came on when I toggled the switch. The CD25D manual is not too clear.Bill wrote: Randy
That is the way mine works (green light on, switch off)....but it is just a power shore switch, no distribution panel....The red light comes on only if there is a polarity switch. (I think polarity is the correct word)
Bill
randy.bates@baesystems.com
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John R.
Reverse polarity light
It is very, very important to understand that a reverse polarity light should have a momentary switch wired between that light and ships ground. If the momentary switch does not exist in your boats AC panel then you need to install one. If you don't have a momentary switch wired as mentioned when you are plugged into shore power your reverse polarity light will always be transferring stray current into your boats common ground system contributing to stray current corrosion. Many Cape Dory boats have this wiring problem. Check your boat!
This is often a very overlooked situation when boats are having stray current problems that are difficult to diagnose.
Most Cape Dory AC panels I have seen will NOT have a momentary switch wired to the reverse polarity light ground connection. Be sure to check your panels and make the wiring retro fit if necessary.
The red AC indicator light is there to indicate *available power*.
An amber light should be your reverse polarity warning indicator. It should only illuminate when there is a detected "reverse polarity" situation while the momentary switch is held in the on position. When the momentary switch is released the light should extinguish. The light should not illuminate at all when the momentary switch is pressed on and there is no "reverse polarity" situation.
This is often a very overlooked situation when boats are having stray current problems that are difficult to diagnose.
Most Cape Dory AC panels I have seen will NOT have a momentary switch wired to the reverse polarity light ground connection. Be sure to check your panels and make the wiring retro fit if necessary.
The red AC indicator light is there to indicate *available power*.
An amber light should be your reverse polarity warning indicator. It should only illuminate when there is a detected "reverse polarity" situation while the momentary switch is held in the on position. When the momentary switch is released the light should extinguish. The light should not illuminate at all when the momentary switch is pressed on and there is no "reverse polarity" situation.
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?
-
Larry DeMers
Re: Reverse polarity light
John,
If the light is not lit (and assuming no series momentary contact switch), then there is no current flowing in the circuit, therefore how can this be - "..The reverse polarity light will always be transferring stray current into your boats common ground system contributing to stray current corrosion."? Where does the stray current come from in this instance?
Usually, the reversed polarity light will be connected to the Neutral and Ground, which normally are bonded together at the service terminal on the dock. If this is true, there is no voltage difference between the two, and there should be no current flow and nothing to worry about..right?
If there IS a polarity reversal, then the Neutral becomes Line, and then there would be a current flow from Line to ground thru the rev. Polarity light. Assuming that the boat is connected properly to the shore power, that ground is earth ground, and there would not seem to be any additional problem with electrolysis
Can you describe the stray current flow problem a bit more please?
Larry DeMers
s/v DeLaMer
Cape Dory 30
demers@sgi.com
If the light is not lit (and assuming no series momentary contact switch), then there is no current flowing in the circuit, therefore how can this be - "..The reverse polarity light will always be transferring stray current into your boats common ground system contributing to stray current corrosion."? Where does the stray current come from in this instance?
Usually, the reversed polarity light will be connected to the Neutral and Ground, which normally are bonded together at the service terminal on the dock. If this is true, there is no voltage difference between the two, and there should be no current flow and nothing to worry about..right?
If there IS a polarity reversal, then the Neutral becomes Line, and then there would be a current flow from Line to ground thru the rev. Polarity light. Assuming that the boat is connected properly to the shore power, that ground is earth ground, and there would not seem to be any additional problem with electrolysis
Can you describe the stray current flow problem a bit more please?
Larry DeMers
s/v DeLaMer
Cape Dory 30
John R. wrote: It is very, very important to understand that a reverse polarity light should have a momentary switch wired between that light and ships ground. If the momentary switch does not exist in your boats AC panel then you need to install one. If you don't have a momentary switch wired as mentioned when you are plugged into shore power your reverse polarity light will always be transferring stray current into your boats common ground system contributing to stray current corrosion. Many Cape Dory boats have this wiring problem. Check your boat!
This is often a very overlooked situation when boats are having stray current problems that are difficult to diagnose.
Most Cape Dory AC panels I have seen will NOT have a momentary switch wired to the reverse polarity light ground connection. Be sure to check your panels and make the wiring retro fit if necessary.
The red AC indicator light is there to indicate *available power*.
An amber light should be your reverse polarity warning indicator. It should only illuminate when there is a detected "reverse polarity" situation while the momentary switch is held in the on position. When the momentary switch is released the light should extinguish. The light should not illuminate at all when the momentary switch is pressed on and there is no "reverse polarity" situation.
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
-
Ken Coit
Re: Reverse polarity light
Randy,
The CD/36 manual has a wiring diagram that shows a momentary Single pole double throw switch between the shore power receptacle and the reverse polarity indicator. The switch selects between the line and neutral wires of the AC mains, before the breakers; normally it is connecting the indicator to the neutral wire. The other side of the indicator is wired to safety ground.
I think that if one uses incadescent bulbs and uses a dual-bulb indicator for reverse polarity that you can have the stray current problem you mention. However, Parfait uses a neon bulb with a current limiting resistor and it is normally between neutral and safety ground where there should be no current. If there is current, the bulb will glow indicating a problem. With a dual incadenscent bulb indicator, there will always be at least one bulb on if the mains are hot and there will be current passing from line and/or neutral to safety ground, thus creating the situation you are concerned with. In that case, the circuit should include a switch.
I think the unswitched indicator is the way to go so that there is constant monitoring of the polarity; of course, from time-to-time one should check to make sure the bulb is still functional.
Keep on sailing,
Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC
parfaitNOSPAM@nc.rr.com
The CD/36 manual has a wiring diagram that shows a momentary Single pole double throw switch between the shore power receptacle and the reverse polarity indicator. The switch selects between the line and neutral wires of the AC mains, before the breakers; normally it is connecting the indicator to the neutral wire. The other side of the indicator is wired to safety ground.
I think that if one uses incadescent bulbs and uses a dual-bulb indicator for reverse polarity that you can have the stray current problem you mention. However, Parfait uses a neon bulb with a current limiting resistor and it is normally between neutral and safety ground where there should be no current. If there is current, the bulb will glow indicating a problem. With a dual incadenscent bulb indicator, there will always be at least one bulb on if the mains are hot and there will be current passing from line and/or neutral to safety ground, thus creating the situation you are concerned with. In that case, the circuit should include a switch.
I think the unswitched indicator is the way to go so that there is constant monitoring of the polarity; of course, from time-to-time one should check to make sure the bulb is still functional.
Keep on sailing,
Ken Coit
CD/14 #538
CD/36 #84 Parfait
Hailing Port: Raleigh, NC
Sailing from: Beaufort, NC
John R. wrote: It is very, very important to understand that a reverse polarity light should have a momentary switch wired between that light and ships ground. If the momentary switch does not exist in your boats AC panel then you need to install one. If you don't have a momentary switch wired as mentioned when you are plugged into shore power your reverse polarity light will always be transferring stray current into your boats common ground system contributing to stray current corrosion. Many Cape Dory boats have this wiring problem. Check your boat!
This is often a very overlooked situation when boats are having stray current problems that are difficult to diagnose.
Most Cape Dory AC panels I have seen will NOT have a momentary switch wired to the reverse polarity light ground connection. Be sure to check your panels and make the wiring retro fit if necessary.
The red AC indicator light is there to indicate *available power*.
An amber light should be your reverse polarity warning indicator. It should only illuminate when there is a detected "reverse polarity" situation while the momentary switch is held in the on position. When the momentary switch is released the light should extinguish. The light should not illuminate at all when the momentary switch is pressed on and there is no "reverse polarity" situation.
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?
parfaitNOSPAM@nc.rr.com
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Randy Bates
Re: Reverse polarity light
John:
The reverse polarity light should NEVER come on regardless of the position of the switch? The switch associated with reversed polarity is a "test for reversed polarity" switch, NOT a "test to see the reversed polarity lamp is NOT burned out" switch? That's what I was afraid of, BUT when I used my volt meter to check all the outlet's polarity, both on the dock AND in the boat all was correct; ie, 0 volts from the ground hole to the large, nuetral slot and 110volts from the ground hole to the smaller slot. I'm now getting confused. Two questions:
1. How can you be sure the reversed polarity lamp is NOT broken w/o a test switch, if there is no provision to test it?
2. If the ground and the nuetral are correctly tied together at the panel why would having a lamp across them cause a current to flow?
Needless to say this has me worried.
randy.bates@baesystems.com
The reverse polarity light should NEVER come on regardless of the position of the switch? The switch associated with reversed polarity is a "test for reversed polarity" switch, NOT a "test to see the reversed polarity lamp is NOT burned out" switch? That's what I was afraid of, BUT when I used my volt meter to check all the outlet's polarity, both on the dock AND in the boat all was correct; ie, 0 volts from the ground hole to the large, nuetral slot and 110volts from the ground hole to the smaller slot. I'm now getting confused. Two questions:
1. How can you be sure the reversed polarity lamp is NOT broken w/o a test switch, if there is no provision to test it?
2. If the ground and the nuetral are correctly tied together at the panel why would having a lamp across them cause a current to flow?
Needless to say this has me worried.
randy.bates@baesystems.com
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Randy Bates
Re: Reverse polarity light
I should have mentioned that the AC panel on my CD25D is the stock CD optional panel. Hopefully it was installed at the factory so it shouldn't be a problem, but I will certainly check it all out.
Thanks again for all your responses
randy.bates@baesystems.com
Thanks again for all your responses
randy.bates@baesystems.com
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John R.
Re: Reverse polarity light
Question #1) Do a continuity test on the bulb if it is incandescent. If continuity ...it's good. Neons will not show any continuity. Neons last an awful long time. Have available a plug in polarity test tool you can insert into a duplex outlet or use your VOM meter in lieu of the reverse polarity light.Randy Bates wrote: John:
The reverse polarity light should NEVER come on regardless of the position of the switch? The switch associated with reversed polarity is a "test for reversed polarity" switch, NOT a "test to see the reversed polarity lamp is NOT burned out" switch? That's what I was afraid of, BUT when I used my volt meter to check all the outlet's polarity, both on the dock AND in the boat all was correct; ie, 0 volts from the ground hole to the large, nuetral slot and 110volts from the ground hole to the smaller slot. I'm now getting confused. Two questions:
1. How can you be sure the reversed polarity lamp is NOT broken w/o a test switch, if there is no provision to test it?
2. If the ground and the nuetral are correctly tied together at the panel why would having a lamp across them cause a current to flow?
Needless to say this has me worried.
Question #2)As Larry mentioned neutral and ground join together at shore. They shouldn't be tied together on board (they should already be isolated on your CD). Remember one leg of your power indicator light is tied into your neutral leg. Return voltage then flows through neutral back to shore. Just like other AC consumers.
Think of water flowing out of a tap (110v supply) and you use some of it (say the power lamp) and the rest of the water (110v) you don't use flows back out a drain. The neutral acts as the drain like a sink drain. I think this clarifies matters.
What it all comes down to is you can use a momentary switch or a neon bulb rather than incandescent. You need to keep your neutral and ground isolated until they join at shore.
I was somewhat vague in the details of my comments but Ken has certainly clarified matters far better with his writting skills than I probably could have. I should have made the distinction between the neon and incandescent bulb. If you have a neon bulb you are okay but many CD's and other boats have an incandescent bulb in their panel. You can do a simple continuity test on the bulb to determine if it is incandescent (showing continuity) or neon (no continuity).
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John R.
Re: Reverse polarity light
See the other discussion in the thread. Power indicator return voltage, tied at breaker.
Larry DeMers wrote: John,
If the light is not lit (and assuming no series momentary contact switch), then there is no current flowing in the circuit, therefore how can this be - "..The reverse polarity light will always be transferring stray current into your boats common ground system contributing to stray current corrosion."? Where does the stray current come from in this instance?
Usually, the reversed polarity light will be connected to the Neutral and Ground, which normally are bonded together at the service terminal on the dock. If this is true, there is no voltage difference between the two, and there should be no current flow and nothing to worry about..right?
If there IS a polarity reversal, then the Neutral becomes Line, and then there would be a current flow from Line to ground thru the rev. Polarity light. Assuming that the boat is connected properly to the shore power, that ground is earth ground, and there would not seem to be any additional problem with electrolysis
Can you describe the stray current flow problem a bit more please?
Larry DeMers
s/v DeLaMer
Cape Dory 30
John R. wrote: It is very, very important to understand that a reverse polarity light should have a momentary switch wired between that light and ships ground. If the momentary switch does not exist in your boats AC panel then you need to install one. If you don't have a momentary switch wired as mentioned when you are plugged into shore power your reverse polarity light will always be transferring stray current into your boats common ground system contributing to stray current corrosion. Many Cape Dory boats have this wiring problem. Check your boat!
This is often a very overlooked situation when boats are having stray current problems that are difficult to diagnose.
Most Cape Dory AC panels I have seen will NOT have a momentary switch wired to the reverse polarity light ground connection. Be sure to check your panels and make the wiring retro fit if necessary.
The red AC indicator light is there to indicate *available power*.
An amber light should be your reverse polarity warning indicator. It should only illuminate when there is a detected "reverse polarity" situation while the momentary switch is held in the on position. When the momentary switch is released the light should extinguish. The light should not illuminate at all when the momentary switch is pressed on and there is no "reverse polarity" situation.
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?
-
Larry DeMers
Re: CD25D AC Panel ..don't add that rev. polarity switch qui
Hi Everyone,
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.
Here is the description of how this circuit operates and why it cannot be a source of "stray current" electrolysis under normal conditions:
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), and Safety Ground (the green wire..used to shunt to ground current shorted to it, protecting the user from shock. It is also a drain for magneticly induced and RF voltages that may be encountered in a radio sensitive electronic circuit).
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.
Where 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.
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.
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. 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).
Cheers,
Larry DeMers
s/v DeLaMer
Cape Dory 30
Lake Superior
demers@sgi.com
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.
Here is the description of how this circuit operates and why it cannot be a source of "stray current" electrolysis under normal conditions:
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), and Safety Ground (the green wire..used to shunt to ground current shorted to it, protecting the user from shock. It is also a drain for magneticly induced and RF voltages that may be encountered in a radio sensitive electronic circuit).
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.
Where 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.
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.
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. 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).
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
-
Ken Coit
One Thing....
Larry,
I agree with everything you say as it applies to what I think was Cape Dory practice across the board.
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
parfaitNOSPAM@nc.rr.com
I agree with everything you say as it applies to what I think was Cape Dory practice across the board.
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
parfaitNOSPAM@nc.rr.com