Earthing a generator

[Leonidas]

My boat has a dedicated sea earth plate onto which the shore power is earthed. The shore power circuit is protected with RCD and each socket with own fuse. There is no direct connection to the negative of the DC circuits. Is there some reason why the generator could not be earthed to a dedicated sea earth and keep things simple?? Obviously there should be a breaker between the generator and shore power as for these two sources of power to run in parallel they will need to be in phase and synchronized, which I do not believe this facility is available in this generator. Anyway, the recommended procedure is to disconnect the shore power before bringing the generator in line.

 

[All_at_Sea]

Just an update on this. I have put a tester on the sockets in the boat when on shorepower and it comes up with live/neutral reversed. Is this right? I am just about to wire in the generator so want to get it right from the start. The concensus is for the generator wiring to be that the generator earth be connected to the neutral wire in the boats 240v circuit.

If the main input from shorepower isn't like this why does the generator need to be? I can easily alter the shorepower wiring so it comes out in the boat corrected, ie mains in with live, neutral and earth all as per the shore power supply. I then need to link in the generator to the same system via a crossover switch and this will use the same wires as the shorepower system. How should l connect the three wires from the generator?

 

[Lon nan Gruagach]

Just an update on this. I have put a tester on the sockets in the boat when on shorepower and it comes up with live/neutral reversed. Is this right? I am just about to wire in the generator so want to get it right from the start. The concensus is for the generator wiring to be that the generator earth be connected to the neutral wire in the boats 240v circuit.

If the main input from shorepower isn't like this why does the generator need to be? I can easily alter the shorepower wiring so it comes out in the boat corrected, ie mains in with live, neutral and earth all as per the shore power supply. I then need to link in the generator to the same system via a crossover switch and this will use the same wires as the shorepower system. How should l connect the three wires from the generator?

live/ neutral swap is always wrong, you can check your boat by measuring connection between the live pin on the shore power inlet plug (captive on your deck)[yes, its a plug even though its fixed] and the mains outlets in your cabin, be sure that you dont have an inverter running!

If you wire your generator correctly then (for that aspect of things) the it makes no difference if the incoming mains is wrong since you must have a switch that selects both live and neutral from shore or generator and that switch will break one set of contacts before making the other.

so, your onboard wiring is:
shore power live and neutral to one input of the switch
generator live and neutral to the other.
the output of the switch to your mains distribution system.
at the generator you should have a link between neutral and earth.

what you do with the earth is a subject of much debate. for me, I would use either a shore power lead with galvanic isolator included or a stand alone GI intermediately after your deck power inlet. Then connect all onboard earths.

It is possible that the marina power is at fault, you could install a switch to swap it back to whats right (your tester is correct so go by that)

 

[All_at_Sea]

Thanks Dolan
Could the wiring in the genny be neutral/earth connected already? I will have a cable coming from it with three wires, blue, brown and earth. I was going to connect this to the crossover switch and join the earths together, so the shorepower, generaotor and mains distribution to the boat would have common earths.

 

[nigelmercier]

Just an update on this. I have put a tester on the sockets in the boat when on shorepower and it comes up with live/neutral reversed. Is this right? I am just about to wire in the generator so want to get it right from the start. The concensus is for the generator wiring to be that the generator earth be connected to the neutral wire in the boats 240v circuit. ...

L/N reverse is clearly not right and needs to be sorted. And now you see into the can of worms that lies behind the N to E conundrum.

 

[VicS]

Thanks Dolan
Could the wiring in the genny be neutral/earth connected already? I will have a cable coming from it with three wires, blue, brown and earth. I was going to connect this to the crossover switch and join the earths together, so the shorepower, generaotor and mains distribution to the boat would have common earths.

The neutral and earth may be connected in the generator but based what others have reported here I think it would be the exception rather than the rule. Easy enough to check by reference to the wiring diagram, if available, or physically.

Technically you could have a system in which neither conductor is earthed but if you do it would be what is described as a "non-polarised" system and all your switching ( including mcbs and RCDs ) should be 2 pole. Fuses, which by their nature are not 2 pole , are not acceptable in a non-polarised system.

You are perfectly correct to join all the earths

 

[Lon nan Gruagach]

The neutral and earth may be connected in the generator but based what others have reported here I think it would be the exception rather than the rule. Easy enough to check by reference to the wiring diagram, if available, or physically.

Technically you could have a system in which neither conductor is earthed but if you do it would be what is described as a "non-polarised" system and all your switching ( including mcbs and RCDs ) should be 2 pole. Fuses, which by their nature are not 2 pole , are not acceptable in a non-polarised system.

You are perfectly correct to join all the earths

In which case normal domestic 13A sockets are out since they are intrinsically part of polarised system, switched outlets only switch live and 13A plugs only fuse live.

 

[VicS]

In which case normal domestic 13A sockets are out since they are intrinsically part of polarised system, switched outlets only switch live and 13A plugs only fuse live.

Thats right Thats why, as I understand it, if you are using UK standard bits and pieces (and non doubly insulated appliances ) You have to stick to a polarised system, requiring a "neutral" to be created in the output of an isolation transformer. an inverter or a generator.

 

[All_at_Sea]

Anyone know a good electrician in or around Trafalgar Wharf?