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Old 21-06-2024, 22:11   #1
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Reverse polarity?

Hi all,
We're currently in Vanuatu and I've just gone to charge up our batteries using our Hush Gensafe portable generator. I've connected it to our shore power inlet and started her up. She's charging great but I've just noticed that the reverse polarity light is on on the shore power panel? From what I've just been googling this is not good. Why would this be happening? When we ARE on shore power the light is not on. Thoughts?
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Old 21-06-2024, 22:27   #2
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Re: Reverse polarity?

because most gennys have a floating ground. the light will come on with most portable gens.

portable gens have no place being on a boat.
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Old 21-06-2024, 23:08   #3
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Re: Reverse polarity?

Hi Smac, thanks for your reply. Can you please elaborate on this? It seems like such a great way to charge the batteries??
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Old 21-06-2024, 23:14   #4
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Re: Reverse polarity?

I suppose my question is: is it safe to use occasionally?
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Old 21-06-2024, 23:37   #5
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Re: Reverse polarity?

Quote:
Originally Posted by Moggatu View Post
I suppose my question is: is it safe to use occasionally?
Yes it is.
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Old 22-06-2024, 03:40   #6
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Re: Reverse polarity?

Portable generators are, generally supplied with a floating [un-bonded] neutral.

Connect [bond] the generator’s neutral wire, to the boat’s grounding electrode system.
The simple way to achieve this, is by connecting the generator’s neutral wire to the generator’s frame, and to the grounding terminal, through a wire or strap.

In a bonded neutral system, the neutral wire provides a low-impedance path, for fault current to flow to the ground, in the event of a fault, thereby reducing the risk of electrical shock, and other hazards.
Bonding the neutral can also help to reduce electrical noise and interference in the system, improving the performance of connected equipment.
This connection creates a common reference point, between the neutral conductor and the earth, preventing a voltage difference [potential], between the neutral conductor, and the ground.


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Old 22-06-2024, 18:55   #7
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Re: Reverse polarity?

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I suppose my question is: is it safe to use occasionally?

it depends which way the boat is facing and what way the wind is blowing, and where the gen is mounted. as multiple people have died from carbon monoxide running a portable gen on a deck before

you also now have the risk of storing a gas tank, and gas jerry cans. neither of which should be inside the boat.

it also possibly violates your boat insurance. as a portable gen on a deck doesn't meat abyc guidelines at all.
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Old 22-06-2024, 20:40   #8
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Re: Reverse polarity?

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Originally Posted by Moggatu View Post
I suppose my question is: is it safe to use occasionally?
Gordmay’s post makes it clear that its not ok and might be dangerous to personnel….. However, I just discovered that the neutral and active on a 15 year old catamaran have been crossed since when the boat was built. Quite accidentally this became apparent while checking the connection of a new AC outlet with a universal power outlet tester, it lit up with a fault light ( AC panel has no dedicated polarity indication) and so did every other outlet on the boat. The problem was in the shore power socket, probably incorrectly wired from new and instantly explained why the owners portable generator had ALWAYS shown reverse polarity on its own built in indicator when plugged into the shore power socket…. No one ever noticed the reverse polarity and the only possible casualty was the early demise of 2 consecutive Heart interface inverter chargers for no apparent reason, (hence the portable generator) and little appetite for shelling out for yet another sacrificial inverter.
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Old 22-06-2024, 22:26   #9
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Re: Reverse polarity?

Thanks Smac. Yes, common sense does need to prevail regarding personal safety but my question really relates to the reverse polarity issue.... will it affect our electronics etc...? Are we ok to charge the batteries without damaging anything?
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Old 22-06-2024, 23:39   #10
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Re: Reverse polarity?

Quote:
Originally Posted by Moggatu View Post
Thanks Smac. Yes, common sense does need to prevail regarding personal safety but my question really relates to the reverse polarity issue.... will it affect our electronics etc...? Are we ok to charge the batteries without damaging anything?
I don't think anyone can answer that question given the variety of wiring standards around the world and what owners may or may not have done to boats over the years. Thankfully neither of us have to worry about ABYC, "couldn't give a hoot" is probably the polite expression.

For some years we charged using a Honda 20i plugged into the shore power connector. Yes the reverse polarity light lit up so we decided to relax with a cup of tea and everything would be alright. Eventually sold the Honda when we increased the solar to the point it wasn't needed anymore.

Thousands of yachts carry a portable generator or dive compressor and used sensibly there isn't a problem.

Pete
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Old 23-06-2024, 01:37   #11
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Re: Reverse polarity?

Safe means different things to Brits, Canadians, Americans, and Australians.

The reverse polarity light means things might be wired better, but it does not mean things won't work. It means that your pants aren't being held up by a belt and suspenders.

Does the shore power lead you have plugged into the generator have 2 wires, or 3?
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Old 23-06-2024, 04:51   #12
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Re: Reverse polarity?

The reverse polarity indicator checks for any voltage between the neutral (white) and ground (green) conductors. Any difference could be due to the hot (black) and neutral being reversed, which is a real reverse polarity condition. With the portable generator's floating ground there can be enough voltage between the two to light the indicator but it's not really reverse polarity. It won't harm any equipment but it is not as shock safe as a bonded ground. ABYC says whatever AC power source you're using must have the neutral and ground bonded at the source, be that in the shore power infrastructure, inverter, or generator. As said above most portable generators do not have a bonded ground. You can buy or make yourself a dummy plug that makes this bond. It is simply a three wire plug with the neutral (usually silver colored) and ground (green) screws connected with a short piece of wire. The brass colored hot screw doesn't get connected to anything. Plug this into the generator's other outlet and the indicator should go out. The generator also should have a grounding terminal, a bare stud marked with the ground symbol. This should be connected to the boat's grounding system.
This takes care of the electrical hazard, but you still have the gasoline and carbon monoxide problems.
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Old 23-06-2024, 13:59   #13
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Re: Reverse polarity?

Thanks Pete! Best answer ever.��
I now have my tea in hand, genie on ( at a safe distance) as I watch the SOC rising nicely. ������
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Old 23-06-2024, 16:47   #14
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Re: Reverse polarity?

Quote:
Originally Posted by donradcliffe View Post
Safe means different things to Brits, Canadians, Americans, and Australians.

The reverse polarity light means things might be wired better, but it does not mean things won't work. It means that your pants aren't being held up by a belt and suspenders.

Does the shore power lead you have plugged into the generator have 2 wires, or 3?
The reverse polarity light means that the neutral in any installed outlet is active and since the switch normally only disconnects the terminal marked “line” or “active” it follows that the power can never be disconnected by turning off the switch, only by disconnecting the shorepower. In the US the neutral terminal in an outlet is often used as a method to power 220 volt appliances by adding an additional active but these are usually dual pole switches. In Australia its a given that land based AC circuits terminate the neutral in the main switchboard at the earth post. My US built boat had isolating transformers and 6 outlets ( stove, washing machine, microwave etc) wired by the manufacturer with hot neutrals as well as the usual active to gain 220v AC. This setup was so unexpected to Australian sparkies that I made up warning plaques for ALL the outlets on the boat and for both main boards.
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Old 29-06-2024, 17:40   #15
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Re: Reverse polarity?

What about outboard motors?
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