Shore Power REVERSE POLARITY Warning - Moderated Discussion Areas

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Author Topic:   Shore Power REVERSE POLARITY Warning

boatmed posted 05-28-2006 07:11 PM ET (US)
Have a new boat. All was well with shore power connected but back at the dock tonite got the REVERSE POLARIY warning light and no power. Shorepower cord is new, same dock pedestal that worked fine for a few days. Any thoughts?
jimh posted 05-29-2006 08:45 AM ET (US)
Typically the REVERSE POLARITY indicator in a boat 115-VAC system is wired between the NEUTRAL and GROUND conductors. If the source of external 115-VAC power is incorrectly wired and has reversed the LINE and NEUTRAL conductors, it will present a voltage of 115-VAC between the NEUTRAL and GROUND conductors on the vessel. This is detected and signaled by the REVERSE POLARITY indicator to alert the vessel electrician that there is a problem with the shore power.
You may have lost shore power due to a circuit breaker tripping, possible a ground-fault interrupter (GFI). In a normal circuit, there should be no current flowing on the safety ground portion of the circuit. If there is a polarity reversal, some current will flow on the ground, perhaps just the current from the polarity reversal indicator mentioned above. This current may be enough to trip off the GFI and interrupt the boat's power.
It is difficult to determine why a particular circuit functioned properly in the past but does not at the present. There may be unanticipated effects from the connection of other vessels to the power distribution. I would contact the wharfinger and ask them to have their electrician verify the wiring of the circuit to which you are connecting.
boatmed posted 05-29-2006 09:04 AM ET (US)
I appreciate the reply. The marina people tell me the problem is with " my boat" since the pedestals are apparently connected in series and the other boats have no problems. Does this make sense? Thanks!
jimh posted 05-29-2006 12:32 PM ET (US)
In any situation where there are two conflicting opinions, seek a third opinion to help resolve the situation. In this case you can obtain an independent third opinion for quite low cost.
Obtain a small circuit analyzer accessory. This will be useful in the future, and the cost is modest. You can usually find these devices sold at home improvement retailers like HOME DEPOT. They look like a small AC plug and have a number of LED indicators. You plug them into a standard 115-VAC outlet and they immediately analyze the circuit and display the results by illuminating the appropriate LED indicators.
See:
http://www.markertek.com/Product.asp?cat=TESTTOOLS&subcat=& prodclass=MULTIMETER&baseitem=SNAP%2D1&search=0&off=0&showreturn=1
for a typical adapter. Cost is $10.
Take your circuit analyzer and plug it into the various power sources on the dock. See if your power source is wired differently than the others.
Most likely you won't be able to plug the analyzer directly into the power plug on the dock if the outlets on the dock are wired with the common circular twist lock connectors. You'll need an adpater. These are also handy to have for future use at marinas. I think there is a international conspiracy in operation which mandates that every marina use a different connector for its electrical outlets. This forces the yachtsman to purchase dozens of connectors and adapters in order to connect.
boatmed posted 05-29-2006 04:57 PM ET (US)
Thanks again for your help. I sure wish you were in Clearwater!
boatmed posted 05-29-2006 05:02 PM ET (US)
Jimh,
By the way, I tried a different power cord and plugged into another pedestal without any results. I have a Promariner galvanic isolator which I think acts like a GFCI for the whole boat. If this went bad could it account for this problem?

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Author	Topic: Shore Power REVERSE POLARITY Warning
boatmed	posted 05-28-2006 07:11 PM ET (US) Have a new boat. All was well with shore power connected but back at the dock tonite got the REVERSE POLARIY warning light and no power. Shorepower cord is new, same dock pedestal that worked fine for a few days. Any thoughts?
jimh	posted 05-29-2006 08:45 AM ET (US) Typically the REVERSE POLARITY indicator in a boat 115-VAC system is wired between the NEUTRAL and GROUND conductors. If the source of external 115-VAC power is incorrectly wired and has reversed the LINE and NEUTRAL conductors, it will present a voltage of 115-VAC between the NEUTRAL and GROUND conductors on the vessel. This is detected and signaled by the REVERSE POLARITY indicator to alert the vessel electrician that there is a problem with the shore power. You may have lost shore power due to a circuit breaker tripping, possible a ground-fault interrupter (GFI). In a normal circuit, there should be no current flowing on the safety ground portion of the circuit. If there is a polarity reversal, some current will flow on the ground, perhaps just the current from the polarity reversal indicator mentioned above. This current may be enough to trip off the GFI and interrupt the boat's power. It is difficult to determine why a particular circuit functioned properly in the past but does not at the present. There may be unanticipated effects from the connection of other vessels to the power distribution. I would contact the wharfinger and ask them to have their electrician verify the wiring of the circuit to which you are connecting.
boatmed	posted 05-29-2006 09:04 AM ET (US) I appreciate the reply. The marina people tell me the problem is with " my boat" since the pedestals are apparently connected in series and the other boats have no problems. Does this make sense? Thanks!
jimh	posted 05-29-2006 12:32 PM ET (US) In any situation where there are two conflicting opinions, seek a third opinion to help resolve the situation. In this case you can obtain an independent third opinion for quite low cost. Obtain a small circuit analyzer accessory. This will be useful in the future, and the cost is modest. You can usually find these devices sold at home improvement retailers like HOME DEPOT. They look like a small AC plug and have a number of LED indicators. You plug them into a standard 115-VAC outlet and they immediately analyze the circuit and display the results by illuminating the appropriate LED indicators. See: http://www.markertek.com/Product.asp?cat=TESTTOOLS&subcat=& prodclass=MULTIMETER&baseitem=SNAP%2D1&search=0&off=0&showreturn=1 for a typical adapter. Cost is $10. Take your circuit analyzer and plug it into the various power sources on the dock. See if your power source is wired differently than the others. Most likely you won't be able to plug the analyzer directly into the power plug on the dock if the outlets on the dock are wired with the common circular twist lock connectors. You'll need an adpater. These are also handy to have for future use at marinas. I think there is a international conspiracy in operation which mandates that every marina use a different connector for its electrical outlets. This forces the yachtsman to purchase dozens of connectors and adapters in order to connect.
boatmed	posted 05-29-2006 04:57 PM ET (US) Thanks again for your help. I sure wish you were in Clearwater!
boatmed	posted 05-29-2006 05:02 PM ET (US) Jimh, By the way, I tried a different power cord and plugged into another pedestal without any results. I have a Promariner galvanic isolator which I think acts like a GFCI for the whole boat. If this went bad could it account for this problem?