Generator reverse polarity

[Gleebitz]

Hi all,

I've just bought a generator to use on my 2700 SE so I can have full power whilst on the water.

When I connect the generator, the reverse polarity light on the switch board is on... but everything seems to work fine. Out of curiosity, I switched the live and neutral cables in the plug to see if that would fix it but no, the light is still on.

Any ideas on this at all?

FYI, I'm on British electrics but I doubt this would make any difference.

[jparsons121]

What type of generator? A portable?

If so, it’s probably a ‘floating neutral’ type and there isn’t any bonding between the neutral and ground (by design!). Therefore, the reverse polarity indicator will light as there is a differential between ground and neutral.

In a properly wired boat, there should not be a neutral-to-ground bond(s) in any part of the shore power electrical system aboard the boat. The shore power neutral-to-ground bond is in the shore power infrastructure, ashore, and comes aboard through the shore power cord.

But with a portable genset, if there is no ground at the generator, there is no known, fixed output polarity to the generated voltage. Which also means that many of the safety features we expect to work - won’t. GFCI protection, alternate ground path for power if a short occurs and the assumption that there is only one ‘hot’ lead (typically black).

So it’s not that the plug has wires swapped, it’s the missing bonding between the neutral and ground that’s supplied by the dockside wiring that causes the indicator to light.

[Gleebitz]

Great reply! Thanks you!

Yeah that makes sense as it’s a portable generator. There’s no earth. I assume that running the generator in this way will not harm the electrical components?

[sph801]

I run a Honda 2200 portable on my 3300 SCR. I have the same issue. I've swapped wires too. Still get the red polarity light but I haven't had a problem with anything. After reading the above post it makes sense.


Sent from my iPhone using Tapatalk

[jparsons121]

It doesn’t harm any of the components, it’s just bypassing a number of the electrical code recommendations so things are “safe” ex: GFCI outlets won’t trip as there is no ground.

[yahoo82]

That light contains a diode that illuminates if the neutral wire has a higher voltage than the ground wire. Which is designed to detect a full 120V fed into the neutral instead of hot but can also illuminate on just a few volts of imbalance between the ground and neutral.

The solution would be to bond the ground and neutral at the generator. This is similar to a house in which all the ground paths are kept separate from the neutrals until the point that the buildings electrical system is grounded.

Here is an article that may be useful for you;

https://www.rvtravel.com/rv-electric...onding-basics/

I made one of these and plugged it into the other generator outlet. I also used a GFCI on the shore power cord at the generator. Probably overkill but I figured it was good practice to be sure that every amp which left the generator came back to the source instead of going somewhere else (ie the water).


Sent from my iPhone using Tapatalk

[jparsons121]

Those Edison plugs will provide the bonding, but only if there isn’t a shore power connection. That’s why most dual source installations use a break-before-make transfer switch. Not only does this prevent a connection between the two sources, they also handle the neutral/grounds as well.