Earthing a portable generator

[Forest Girl]

Portable suitcase type generators are supposed to be earthed. I have just bought one. It has an earth bolt/nut on the side. Any useful info on earthing them on a boat would be very much appreciated. It would be used direct into shore power inlet for charging batteries.
Thanks everyone.

 

[VicS]

Portable suitcase type generators are supposed to be earthed. I have just bought one. It has an earth bolt/nut on the side. Any useful info on earthing them on a boat would be very much appreciated. It would be used direct into shore power inlet for charging batteries.
Thanks everyone.

Been discussed at length on here before. A search or two should find it all.

IIRC there is nothing useful you can do with the earthing terminal, although ashore this in theory should be connected to earth spike in the ground.

If you plug it in to the shore power connection that should make the connection to the boats own internal " earth " that is necessary for its safe use on board.

You dont say what make and model though!

 

[Richard10002]

I have a dedicated generator lead which has its earth and negatives joined inside the plug that goes into the generator. You must not use this lead for a shore power connection!!!

Without this, the circuit breakers on the boat don't blow, and my 240V circuit tester shows a "no earth" fault.

Having read loads on here, on ybw.com, and the Web in general, the above seems to be the best solution, (to me).

 

[rogerthebodger]

I have a dedicated generator lead which has its earth and negatives joined inside the plug that goes into the generator. You must not use this lead for a shore power connection!!!

Without this, the circuit breakers on the boat don't blow, and my 240V circuit tester shows a "no earth" fault.

Having read loads on here, on ybw.com, and the Web in general, the above seems to be the best solution, (to me).

And for me. The so called earth bolt on the chassis of the generator is worse than useless and potential dangerous.

Any source of mains power including inverters, generators and isolation transformers must have the earth wire and neutral wire connected at the power source otherwise you will have in effect a balanced power system and any RCD will not work.

It is in effect this earth to neutral connection that makes the neutral what it neutral.

Just to make a point if you don't mine then overload circuit breaker may trip when there is no earth it the residual current circuit breaker that will not as no residual current can flow without the earth/neutral connection.

 

[Laundryman]

"Any source of mains power including inverters, generators and isolation transformers must have the earth wire and neutral wire connected at the power source otherwise you will have in effect a balanced power system and any RCD will not work.

It is in effect this earth to neutral connection that makes the neutral what it neutral."

Sorry but we have been here many times and i'm still not 100% convinced. Are you saying that the socket on the pontoon already has its neutral and earth connected or are you suggesting that my plug that goes into that socket should have the neutral and earth connected. Or... is it just a portable mains supply that should be connected as such.
I'm not arguing. I'm a user, not an expert and I just want a clear definitive answer. I want to plug my shorepower lead into either the pontoon or generator. If I need a different lead for each so be it. Thanks Alan

 

[rogerthebodger]

inverters, generators and isolation transformers must have the earth wire and neutral wire connected at the power source

If your pontoon box has an isolation transformers the earth /neutral should be connected inside the pontoon box so there is no need fore your lead that plugs into the socket at the pontoon box to have its earth/neutral connected.

If you have either an inverters, generators and isolation transformers on your boat these need earth/neutral connections.

Get a mains tester as described to see if this setup applied to you or any pontoon box you connect to.

 

[Laundryman]

Thank you. All is now clear.........till someone else comes along to muddy the waters!

 

[Richard10002]

"Any source of mains power including inverters, generators and isolation transformers must have the earth wire and neutral wire connected at the power source otherwise you will have in effect a balanced power system and any RCD will not work.

It is in effect this earth to neutral connection that makes the neutral what it neutral."

Sorry but we have been here many times and i'm still not 100% convinced. Are you saying that the socket on the pontoon already has its neutral and earth connected or are you suggesting that my plug that goes into that socket should have the neutral and earth connected. Or... is it just a portable mains supply that should be connected as such.
I'm not arguing. I'm a user, not an expert and I just want a clear definitive answer. I want to plug my shorepower lead into either the pontoon or generator. If I need a different lead for each so be it. Thanks Alan

As far as I can tell, the earth and neutral are connected at the power station in a shore based mains power system, which is why we don't have to worry about doing it ourselves. In fact, we must not do it ourselves, hence my explanation marks above.

I dont present to understand how this all works.

 

[rogerthebodger]

As far as I can tell, the earth and neutral are connected at the power station in a shore based mains power system

The earth/neutral connection is more likely at the transformer substation than the power station. The substation is very much like an isolation transformer except the substation generally reduces the voltage from the generation voltage to something more usable by the general public, as well as providing isolation. An isolation transformer used on boats will be 1 to 1 voltage

 

[GrahamM376]

And for me. The so called earth bolt on the chassis of the generator is worse than useless and potential dangerous.

Any source of mains power including inverters, generators and isolation transformers must have the earth wire and neutral wire connected at the power source otherwise you will have in effect a balanced power system and any RCD will not work.

It is in effect this earth to neutral connection that makes the neutral what it neutral.

Just to make a point if you don't mine then overload circuit breaker may trip when there is no earth it the residual current circuit breaker that will not as no residual current can flow without the earth/neutral connection.

I never bother with the earth tag on my Honda and the on board rcd works fine, may or may not be bonded within the generator. No way will I modify the connecting lead (as suggested by another poster) as with euro sockets, there's a 50/50 chance of polarity reversal.

 

[rogerthebodger]

I never bother with the earth tag on my Honda and the on board rcd works fine, may or may not be bonded within the generator. No way will I modify the connecting lead (as suggested by another poster) as with euro sockets, there's a 50/50 chance of polarity reversal.

Your Honda may already as you say be bonded and one of these plug in mains testers will confirm. I know my Honda EM1000 does not have earth/neutral bonding so I did the same a Richard. My Honda has an unusual connection on the generator that will not fit any where else so it quite safe.

I also have 2 neons fitted to my incoming shore power panel that will show any missing earth or polarity reversal but a mains tester will do the same.

 

[ianj99]

As far as I can tell, the earth and neutral are connected at the power station in a shore based mains power system, which is why we don't have to worry about doing it ourselves. In fact, we must not do it ourselves, hence my explanation marks above.

I dont present to understand how this all works.

The reason for it is very simple if you think about how the rcd on your boat/home etc works.
It trips if the current flowing out the live exceeds that returning via the neutral by more than 10 or 30ma (or whatever the rcd trip current is).

So how can this happen? If there is a leak, to make sure this is as big as possible (ie to ensure rapid tripping), there must be as many paths to earth as possible. In other words, by providing alternate paths for the leakage other than via the negative, tripping is assured.

This also shows why the N & E must be joined BEFORE the rcd (ie at the generator/transformer/substation side) so the leakage current bypasses the rcd, ensuring it trips.

 

[Richard10002]

I never bother with the earth tag on my Honda and the on board rcd works fine, may or may not be bonded within the generator. No way will I modify the connecting lead (as suggested by another poster) as with euro sockets, there's a 50/50 chance of polarity reversal.

Are they euro sockets on board, or do you mean the shore power supply?

I could find no other way to make the RCD work, so not much choice really, other than to risk a dangerous leak on board.

 

[GrahamM376]

Are they euro sockets on board, or do you mean the shore power supply?

I could find no other way to make the RCD work, so not much choice really, other than to risk a dangerous leak on board.

My Honda 2kw was purchased in Portugal so is fitted with 2 x euro sockets, not 3 pin UK type. Also, the boatyard I use has cra**y electrics with 2 pin sockets so no telling polarity and someone measured 90 volts on the earth circuit after getting a tingle from his hull.

RCD does not rely on there being an earth circuit, it looks for imbalance between live and neutral.

One problem I had (but only at Alcoutim) was immediate tripping of the shoreside pontoon RCD whenever I plugged in. In the end it turned out to be a new inverter I had fitted which, although not switched on, had the neutral and earth bonded internally. I keep my boat 240v circuit isolated from everything.

 

[rogerthebodger]

Also, the boatyard I use has cra**y electrics with 2 pin sockets so no telling polarity and someone measured 90 volts on the earth circuit after getting a tingle from his hull.

Thats what you get when you have a balances system where there is earth to ensure correct reference to ground

RCD does not rely on there being an earth circuit, it looks for imbalance between live and neutral.

That statement is only half correct. For there to be an imbalance current between the live and neutral that imbalance must go somewhere. It will either go down the earth wire back to the neutral earth connection at the substation or through the ground to the earth spike also at the substation which is also connected to the earth wire and the neutral.

This is all in accordance to one of the fundamental laws of electricity Kirchhoff's current law. Google it and find out what it says.

Also look here

http://en.wikipedia.org/wiki/Ground_and_neutral

 

[GrahamM376]

For there to be an imbalance current between the live and neutral that imbalance must go somewhere. It will either go down the earth wire back to the neutral earth connection at the substation or through the ground to the earth spike also at the substation which is also connected to the earth wire and the neutral.

Or of course to ground through the person touching the wire:angel:

 

[rogerthebodger]

Or of course to ground through the person touching the wire:angel:

What do you mean "to ground" what do you call ground and where does the electric current go to once it has passed "to what you call ground".

As I said

" or through the ground to the earth spike also at the substation which is also connected to the earth wire and the neutral "

 

[Graham_Wright]

As far as I can tell, the earth and neutral are connected at the power station in a shore based mains power system, which is why we don't have to worry about doing it ourselves. In fact, we must not do it ourselves, hence my explanation marks above.

I dont present to understand how this all works.

There is no neutral at the power station! A glance at a pylon will show groups of three cables (plus possibly one on the top that is obviously connected to the pylon framework).

Neutral is made at the substation/transformer.

Our domestic supply is called PME, Protective Multiple Earth, and every supply to a property has the neutral lead bonded to the earth and also to a plate buried in the earth.

Bearing in mind that, e.g., the French don't really understand (!) earths or polarity, connecting your earth and neutral together could be "interesting" if the shore supply is reversed.

 

[prv]

Our domestic supply is called PME, Protective Multiple Earth

Well, it can be. It can also be TT or TN-S.

Pete

 

[GrahamM376]

What do you mean "to ground" what do you call ground and where does the electric current go to once it has passed "to what you call ground".

As I said

" or through the ground to the earth spike also at the substation which is also connected to the earth wire and the neutral "

The point I am trying to make is that an RCD will trip when a person touches the live wire thus creating an imbalance, regardless of whether there's a physical earth wire anywhere in the circuit. If I use a plug-in RCD in my generator cable, it works although the generator itself and the lead do not have any earth connections.