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Old 20-03-2017, 12:30   #1
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Reverse Polarity Indicator with a Galvanic Isolator ?

I have a Safeshore Gavanic Isolator installed on my boat ..

The galvanic isolator is like a switch. It fits in the “earth” circuit of your boat shore power line & the switch is “open circuit”...(turned off). This makes a break in the earth wire & stops the flow of any current through the “earth” wire. This now protects your vessel from contact with other boats so galvanic current cannot flow from one boat to another. It also protects you from defective shore power low level earth leaks.(Sometimes the shore power 240 volt “live” cable leaks voltage to the earth cable via damp plugs & sockets or leaky cables: This is known as stray current leakage & puts unwanted voltages directly onto your props & shafts etc & if the voltage is high this can be devastating to your metal ware!). Most galvanic isolators have a “switch on threshold” of 1.2 volts.



I have recently fitted a Blue Sea AC distribution 3 way switch with reverse polarity indicator lights. These lights seem to use a voltage differential between the neutral and ground wires. As I understand it, these two wires are connected onshore, there is no differential - and no light. If you swap the live where the neutral should be, there is a differential and then the lights come on... assuming a polarity swap.


so.... i seem to have the reverse polarity lights on for both Shore Power and Generator.
I am assuming that because of the Galvanic Isolator (breaking the ground circuit) these will always show on ?
And the Generator does not combine the neutral and ground ?


Have i got this right ?
Is there a way round this situation ?
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Old 21-03-2017, 01:27   #2
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Re: Reverse Polarity Indicator with a Galvanic Isolator ?

Quote:
Originally Posted by d4raffy View Post
I have a Safeshore Gavanic Isolator installed on my boat ..

The galvanic isolator is like a switch. It fits in the “earth” circuit of your boat shore power line & the switch is “open circuit”...(turned off). This makes a break in the earth wire & stops the flow of any current through the “earth” wire. This now protects your vessel from contact with other boats so galvanic current cannot flow from one boat to another. It also protects you from defective shore power low level earth leaks.(Sometimes the shore power 240 volt “live” cable leaks voltage to the earth cable via damp plugs & sockets or leaky cables: This is known as stray current leakage & puts unwanted voltages directly onto your props & shafts etc & if the voltage is high this can be devastating to your metal ware!). Most galvanic isolators have a “switch on threshold” of 1.2 volts.



I have recently fitted a Blue Sea AC distribution 3 way switch with reverse polarity indicator lights. These lights seem to use a voltage differential between the neutral and ground wires. As I understand it, these two wires are connected onshore, there is no differential - and no light. If you swap the live where the neutral should be, there is a differential and then the lights come on... assuming a polarity swap.


so.... i seem to have the reverse polarity lights on for both Shore Power and Generator.
I am assuming that because of the Galvanic Isolator (breaking the ground circuit) these will always show on ?
And the Generator does not combine the neutral and ground ?


Have i got this right ?
Is there a way round this situation ?
Not sure whether generator should combine PE and N - consult ABYC folks for a definitive answer, and also did you put your voltmeter across PE and N when RPLs were lit? If yes, what was the readout?

Nevertheless, if you suspect that the voltage level shift coming from GI insertion in the PE circuit is the cause of lit RPLs , build the circuit pictured and insert it in series with the RPL. Total cost to build shouldn't exceed $1.

See if it helps.
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Old 21-03-2017, 06:46   #3
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Re: Reverse Polarity Indicator with a Galvanic Isolator ?

I keep my electrical systems completely isolated. I have a 30 amp main for shore power, and a separate 30 amp main for the generator. I only close the circuit of the one I am using.
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Old 21-03-2017, 07:07   #4
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Re: Reverse Polarity Indicator with a Galvanic Isolator ?

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Originally Posted by Scot McPherson View Post
I keep my electrical systems completely isolated. I have a 30 amp main for shore power, and a separate 30 amp main for the generator. I only close the circuit of the one I am using.
I think we all do? In my case the switch is automatic, but will only allow connection of one or the other. I am not sure what would happen if a generator and shore power were paralled, but I assume it would not be good for the generator?

The other issue would be that if shore power were off, then you would be powering the system from the boat, meaning that you could electrocute someone working on the shore?
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Old 21-03-2017, 07:12   #5
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Re: Reverse Polarity Indicator with a Galvanic Isolator ?

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Originally Posted by Scot McPherson View Post
I keep my electrical systems completely isolated. I have a 30 amp main for shore power, and a separate 30 amp main for the generator. I only close the circuit of the one I am using.
Yes - we all do - that is what the Blue Sea switch is for. .... to keep shore power, Geni and Inverter isolated...



but .. that has nothing to do with my question !
What effect does the GI have on the RPL's that are boat side ....
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Old 21-03-2017, 22:29   #6
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Re: Reverse Polarity Indicator with a Galvanic Isolator ?

The galvanic isolator is not a switch. You have a constant ac ground all the time. It blocks dc current

The galvanic isolator shiuld not be in the gen circuit. So would have nothing to do with the gen rev pol light going on. And yes the gen ground and n should be joined at gen. hard wired.

Sounds like you have a wiring issue. Easy to check with a volt meter if you know what you are doing.
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Old 02-04-2017, 03:39   #7
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Re: Reverse Polarity Indicator with a Galvanic Isolator ?

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The galvanic isolator is not a switch. You have a constant ac ground all the time. It blocks dc current

The galvanic isolator shiuld not be in the gen circuit. So would have nothing to do with the gen rev pol light going on. And yes the gen ground and n should be joined at gen. hard wired.

Sounds like you have a wiring issue. Easy to check with a volt meter if you know what you are doing.
well thanks smac999 - you were spot on.
BTW . The galvanic isolator is only on the shore power feed.

I bought a plug in socket tester with a shore power connector - this proved the shore power was all good and gave me a reference to verify my plug connector orientation - and yes - mine was wired incorrectly ! 10 years like that (from the factory) and i never knew until i fitted this Blue Sea switch.

Next was the Generator. Thanks to the very helpful guy from Advanced Yacht Systems that spotted that wiring mistake The yellow wire connected to the earth was infact the centre phase connection. Had to fit a earth to neg loop and also connect to the chassis. Apparently no danger but all good now.

thanks all .....
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