Shore Power socket causing reverse polarity? Maybe

[Chrisjunker]

Hi Cruisers.

So I am having a really tough time trying to figure out why I keep getting the reverse polarity light on my switchboard panel. Could someone please give some advice? As I am going to freeze soon without a hot shower here in Belgium.

I will try be as clear as possible.
I am the new owner of this boat. 37ft Endeavour. Not that new around 4 years now. I have been working a lot the past few years so I am finally getting to enjoy her this past summer. Trying all systems now and getting everything up and running. I am in Belgium at the moment.

So its an American boat. I am in Europe. I need a step up step down transformer to plug this baby in. I did this and first thing I see is the polarity reverse light is on. I called the old owner who has been helping me a lot and he suggested to switch the hot and neutral wires on the shore power socket. As he might have done this before somewhere in Greece.
Lovely! It works. I can finally use all the systems onboard and not rely on my 12v system and the weak Belgium sun for power. Fridge and water heater are now running off shorepower.

Then about a week later. I get the reverse polarity light again. How is this possible as I just switched the wires last week? I check at the switchboard panel and all is correct. I thought it might have been something wrong on the little orange NEMA extension cable that I use. Doesn't seem so I checked it.
Was it maybe all the rain over the past week that seeped into the cable where it connects into the extension cable outside before it connects into the transformer?
Maybe? Can that cause reverse polarity, I don't think so?
Its been dry for a week and I tried this all again, same thing. I need hot water its cold now!
Same thing happens, plug it all up,
Fridge turns on, 10 seconds later it trips, and the light shows reverse polarity again, but only after the fridge trips. So it doesn't show reverse polarity then after the fridge trips it does and continues to show so the rest of the day.

My question. (If you have some advice about the above please say so?)
I replaced the owners old USA style shore power cable as it showed burn marks. I am now using my new Marinco pigtail adapter as shown in picture. But i've noticed that the shore power socket has burn marks on it. The old owner has confirmed these were there for a long time. I definitely want to replace this ASAP.
But do you think these burn marks are causing all the reverse polarity and power trips nonsense. I can't figure out what else might cause this other than that being the dodgey connection. Also as my 2000w Transformer is new as well as my pig tail cable.

Long story I know, just wanted to give all details.
Any tips?
Thank you!

[Jammer]

I don't think the burn marks have anything to do with it. I would imagine that it is due to an interaction between how the marina outlet and the step-down transformer are wired.


You should clean up the oxidation on the blades of the shore power inlet using a wire brush or some sandpaper or emery cloth. That won't fix your polarity problem, but it will reduce the likelihood of overheating.

[Be Free]

If my shore power inlet had burn marks and corrosion like that I'd replace it.



If I were replacing it I would give a lot of consideration to replacing it with a more modern connector like a Smart Plug.


Your boat. Your rules.


In a US wired boat, the reverse polarity light on the AC panel should simply indicate that there is a voltage potential between the neutral and the safety ground. In the US that would usually indicate that the neutral and load wires are swapped.

[stormalong]

Originally Posted by Be Free

If my shore power inlet had burn marks and corrosion like that I'd replace it.



If I were replacing it I would give a lot of consideration to replacing it with a more modern connector like a Smart Plug.


Your boat. Your rules.


In a US wired boat, the reverse polarity light on the AC panel should simply indicate that there is a voltage potential between the neutral and the safety ground. In the US that would usually indicate that the neutral and load wires are swapped.

Be Free is right. Because you are using a transformer there is a voltage difference between the neutral wire and ground. When I have used a transformer it was necessary to disconnect the ground leg of the triple circuit breaker in my panel. Not much you can do about it. The transformer isolates the output from the mains power - there will always be a difference. The only thing you could do would be to fool your ground fault protection by wiring the ground lead at the transformer to one of the outputs and make that your neutral going into the boat.

PS. I would replace that connector with a SmartPlug too. Already done on my boat.

[Jammer]

Originally Posted by stormalong

Because you are using a transformer there is a voltage difference between the neutral wire and ground.

Depends.


Many 240v-120v transformers are autotransformers that, by their design, have a common neutral between input and output. Even those transformers that have separate primary and secondary windings can have the input neutral and the output neutral connected together.


But if the neutral and hot are reversed at the input to the transformer, the 240v hot is carried through, and you end up with one output leg at 120v to ground and the other output leg at 240v to ground, so that the "polarity" indicator will be active, and will remain so even if the leads at the boat are reversed.


Transformers designed to serve as either step-up or step-down are sometimes designed without polarized plugs and may lead to this problem.

[Chrisjunker]

Originally Posted by stormalong

Be Free is right. Because you are using a transformer there is a voltage difference between the neutral wire and ground. When I have used a transformer it was necessary to disconnect the ground leg of the triple circuit breaker in my panel. Not much you can do about it. The transformer isolates the output from the mains power - there will always be a difference. The only thing you could do would be to fool your ground fault protection by wiring the ground lead at the transformer to one of the outputs and make that your neutral going into the boat.

PS. I would replace that connector with a SmartPlug too. Already done on my boat.

Hi thanks for replies guys.

Ok I am going to try this today? So first thing just remove the ground wire at my circuit breaker? Is that all I have to do and give it a go?

[goboatingnow]

If your polarity light is now on the output of the transformer is now nonsense as it’s connected to shore earth. Nothing should be connected to shore earth on board if an isolating transformer is being used.

The polarity light only makes sense now on the input lead to the transformer.

Shore earth should only be connected to the isolating transformer if metallic case , if not don’t connect it all.

On board your original earth should now terminate at the designated output neutral of the isolating transformer . Preferably this earth should not be seawater connected.

[Rumrace]

I love electricians. Seems a few here. I seem to get same problem but only in one haunt so I just don’t plug in. Also an extension cord 120.
Learned lots thank you.

[Icarus]

Originally Posted by Chrisjunker

Hi Cruisers.



So I am having a really tough time trying to figure out why I keep getting the reverse polarity light on my switchboard panel. Could someone please give some advice? As I am going to freeze soon without a hot shower here in Belgium.



I will try be as clear as possible.

I am the new owner of this boat. 37ft Endeavour. Not that new around 4 years now. I have been working a lot the past few years so I am finally getting to enjoy her this past summer. Trying all systems now and getting everything up and running. I am in Belgium at the moment.



So its an American boat. I am in Europe. I need a step up step down transformer to plug this baby in. I did this and first thing I see is the polarity reverse light is on. I called the old owner who has been helping me a lot and he suggested to switch the hot and neutral wires on the shore power socket. As he might have done this before somewhere in Greece.

Lovely! It works. I can finally use all the systems onboard and not rely on my 12v system and the weak Belgium sun for power. Fridge and water heater are now running off shorepower.



Then about a week later. I get the reverse polarity light again. How is this possible as I just switched the wires last week? I check at the switchboard panel and all is correct. I thought it might have been something wrong on the little orange NEMA extension cable that I use. Doesn't seem so I checked it.

Was it maybe all the rain over the past week that seeped into the cable where it connects into the extension cable outside before it connects into the transformer?

Maybe? Can that cause reverse polarity, I don't think so?

Its been dry for a week and I tried this all again, same thing. I need hot water its cold now!

Same thing happens, plug it all up,

Fridge turns on, 10 seconds later it trips, and the light shows reverse polarity again, but only after the fridge trips. So it doesn't show reverse polarity then after the fridge trips it does and continues to show so the rest of the day.



My question. (If you have some advice about the above please say so?)

I replaced the owners old USA style shore power cable as it showed burn marks. I am now using my new Marinco pigtail adapter as shown in picture. But i've noticed that the shore power socket has burn marks on it. The old owner has confirmed these were there for a long time. I definitely want to replace this ASAP.

But do you think these burn marks are causing all the reverse polarity and power trips nonsense. I can't figure out what else might cause this other than that being the dodgey connection. Also as my 2000w Transformer is new as well as my pig tail cable.



Long story I know, just wanted to give all details.

Any tips?

Thank you!

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Attachment 265328

I have a US boat wired the same way, I used the same style step down transformer 240V shore to 110 V as my water heater is wired for 110V.
All the various outlets as well.
After having this rather awkward set up for years, when the water heater finally broke I got a 240V heater.
I rewired the US AC board ( 2 hot wires +1 ground) to 1 Active, 1 Neutral, 1Ground to the existing main circuit breaker)
I also installed Australian style 240V outlets.
Checked all power outlets for polarity and for some reason 2 outlets were wired neutral to ground...and kept throwing the outlet breaker circuit breaker when plugging in a vacuum cleaner.
All you need is multimeter and check each outlet for polarity. According to how the marina shore power is wired...Active, Neutral and Earth
US has different wire colour coding then and Australia.
We have Active brown, Neutral blue and Earth Green/Yellow same as EU

[goboatingnow]

Those Marinco plugs on 230vac are total junk products. They burn out contacts repeatedly ,get rid of then and switch to IEC 60309 ( “ blue commando “) replace the boats socket as well.

Secondly if you are using a transformer there is a risk you have a floating neutral this would trip the polarity light

Really in 230 vac land reverse polarity can be meaningless ac neutral assuming and rcd should not be connected to seawater in the boat

Yuh need to test continuity on your circuits to ensure your wiring is sound.

Few EU for good reasons have “ polarity lights “ they are a US predilection. I don’t have one abs hence it doesn’t worry me.

[smac999]

Originally Posted by goboatingnow

Really in 230 vac land reverse polarity can be meaningless ac neutral assuming and rcd should not be connected to seawater in the boat

Yuh need to test continuity on your circuits to ensure your wiring is sound.

Few EU for good reasons have “ polarity lights “ they are a US predilection. I don’t have one abs hence it doesn’t worry me.

EU 230v is an ungrounded hot, a grounded neutreal, and a grounding cable. Exact same as usa 120v.

Both need correct polarity or can be dangerous.

[goboatingnow]

Originally Posted by smac999

EU 230v is an ungrounded hot, a grounded neutreal, and a grounding cable. Exact same as usa 120v.

Both need correct polarity or can be dangerous.

Not so. Many European installations have floating neutrals. In some cases 230vac is derived from you split phase supply 3 phase supply and floating neutrals , it’s very unwise to assume neutral is at earth potential.

Basically U.K. and Ireland follow the us model of grounded neutrals but that’s not EU wide

Tne diference in Europe is unpolarised mains is extremely common. The standard Schuko 2 pin socket is unpolarised

Hence it’s extremely unwise to assume neutral is “ dead “. Hence you not see “ inverted polarity “ lights on European AC panels as a matter of course.

If the boat is fitted with a RCD and wired to RCD standards there no issue with inverted polarity and there’s no need to be worried about it.

[smac999]

Originally Posted by goboatingnow

Not so. Many European installations have floating neutrals. In some cases 230vac is derived from you split phase supply 3 phase supply and floating neutrals , it’s very unwise to assume neutral is at earth potential.

Basically U.K. and Ireland follow the us model of grounded neutrals but that’s not EU wide

Tne diference in Europe is unpolarised mains is extremely common. The standard Schuko 2 pin socket is unpolarised

Hence it’s extremely unwise to assume neutral is “ dead “. Hence you not see “ inverted polarity “ lights on European AC panels as a matter of course.

If the boat is fitted with a RCD and wired to RCD standards there no issue with inverted polarity and there’s no need to be worried about it.

So wire your house backwards. Turn off a light switch. (Which is supposed to switch off the hot, but if it’s backwards it shuts off the neutreal not the hot. ). Now stick your figure in the socket while changing the light bulb

A 30ma rcd is not going to save you. . So unless you wire all your light switches double pole. You need correct polarity with a grounded neutreal…

[goboatingnow]

Originally Posted by smac999

So wire your house backwards. Turn off a light switch. (Which is supposed to switch off the hot, but if it’s backwards it shuts off the neutreal not the hot. ). Now stick your figure in the socket while changing the light bulb

A 30ma rcd is not going to save you. . So unless you wire all your light switches double pole. You need correct polarity with a grounded neutreal…

Why would you stick you fingers in a sockets

Secondly of course the RCD TRIPS

clearly you don’t understand Mains wiring reverse polarity is extremely common. The neutral IS a live wire

[Pete7]

Originally Posted by goboatingnow

clearly you don’t understand Mains wiring reverse polarity is extremely common. The neutral IS a live wire

Indeed, UK and Ireland yachts often find that plugging into European shorepower causes the warning lights to show a reversed polarity. Not unknown for yachts to carry a second pig tail with reversed live and neutral wires to resolve this.

Can be confusing for Europeans to get their heads around US wiring, equally Americans understanding European wiring. Terminology doesn't help either.

Pete