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Shore power

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My boat has an inverter fitted on it and a ring main consisting of 3 sockets,if I plumb shore power into the existing consumer unit would I still need a splitter switch even though the Inverter has a on/off switch in the cabin?


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An inverter is an isolated power supply, and must never be on when you are connected to shore power. The first time you forget, will be the end for the inverter immediately. I would strongly suggest fitting at least a manual rotary select three pole switch which you would switch to either connect the inverter or shore power to the consumer unit and therefore the rest of the boat. Sterling power sell them on their website. They also sell a rather nice automatic change over switch. This has priority inputs and will automatically choose the source power depending on what is available. So you might have shore power as priority one, a genny as priority two and the inverter as priority three. As soon as a source of the highest priority becomes available it will automatically switch to it. The automatic switches often have an isolation circuit as well, to isolate some sockets when running on a source with restricted power. For instance if you were running on inverter power, you wouldn't want your battery chargers on. So these would be connected to the isolation circuit and would only come on when on shore power or genny.

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The automatic change over switch is certainly the very best way to do it, but there is also a much cheaper and easier method, that is also 100% safe, albeit needing you to manually make the change whenever you use the alternative source.

Using standard 15amp "hook-up" type cheap fittings, you can fit a bulkhead mounted input plug close to the boats consumer unit, (inside the boat).

You then fit a 15 amp hook up line socket to your incoming hookup mains supply lead (from the existing external hook-up bulkhead plug).

You then fit another 15 amp line socket to the output of your inverter.

Then you just insert whichever line socket you are currently getting the power from into your consumer unit's input plug.

That way the two power sources are completely isolated, and the cost is about £10. (for the two line sockets and one bulkhead plug). :)

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  • 2 weeks later...

Got my sterling power manual cross over switch today,now reading through the brief instructions I notice that the Earth wire doesn't go to the switch but by- passes it and goes direct to the consumer unit,now I was wondering what would be the best way to join 3 earth wires together,I was thinking maybe a Bus bar ?

Any ideas


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Nah Andy, it's the broads, a household chocolate block will be perfect, also don't forget to use ordinary solid copper core mains cable throughout, or just twist ‘em and cover with tape preferably masking tape. :naughty:

Seriously.... a bus bar is ideal, get one with an insulated cover and the job'll be a good un. When you have done it may pay you to have it checked by a qualified marine electrician just for peace of mind.

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  • 3 weeks later...

It might sound a bit "Heath Robinson" Andy, but I've always found the plugs method to be simple, quite neat, and 100% safe.

The fact that it's also a fraction of the cost is pure gravy. :)


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