Making a safe ground for generator use

Colvic Watson

Well-known member
Joined
23 Nov 2004
Messages
10,891
Location
Norfolk
Visit site
I tried to make sense of someone else's generator/earth thread but it got very angry very quickly, so apologies if this looks like a repeat.

We use a petrol powered genny most of the year as we’re either anchored or on a non electric connected harbour pontoon. The generator has an earth connection which I could easily make with a wire running to the salt water; but the onboard consumer unit doesn’t have a ground to earth connection. Is it possible via a simple skin fitting similar to an anode stud through the hull?

Thank you.
 

Tranona

Well-known member
Joined
10 Nov 2007
Messages
42,202
Visit site
That is exactly how I did my 240v system. Actually used a button anode and its through hull bolt. Commonly used by production builders such as Bavaria While the 2013 RCD regs require it on new boats it is not retrospective and thousands of earlie boat around without grounded 240V systems.
 

Colvic Watson

Well-known member
Joined
23 Nov 2004
Messages
10,891
Location
Norfolk
Visit site
That is exactly how I did my 240v system. Actually used a button anode and its through hull bolt. Commonly used by production builders such as Bavaria While the 2013 RCD regs require it on new boats it is not retrospective and thousands of earlie boat around without grounded 240V systems.
Thank you - brilliant!
 

lustyd

Well-known member
Joined
27 Jul 2010
Messages
12,299
Visit site
Yes that was essentially what Paul R said to do on my thread. I have gone with a cable screwed to the earth on the generator and into the water using an old anode as a weight since I didn't want to drill a hole in the hull while afloat, but longer term will probably add one as above.
 

Colvic Watson

Well-known member
Joined
23 Nov 2004
Messages
10,891
Location
Norfolk
Visit site
Yes that was essentially what Paul R said to do on my thread. I have gone with a cable screwed to the earth on the generator and into the water using an old anode as a weight since I didn't want to drill a hole in the hull while afloat, but longer term will probably add one as above.
Thank you, I found your thread question helpful but I didn’t get that far in the answers, I got lost in the vitriol! Quick, how do I lock this thread? I’ve got the answer I need and I don’t want the angry mob to wreck it 😁😁😁
 

oldmanofthehills

Well-known member
Joined
13 Aug 2010
Messages
5,061
Location
Bristol / Cornwall
Visit site
The idea of local earth is to stop mains going back via your body and the ground and killing you if a fault occurs.

However normal mains is relative to earth via the great big 11kv to 450v three phase transformers such that each phase relative to the others is 450 but each phase to an imaginary centre point is 240v. So 240v goes out via one of the phases plus a neutral connected at the transformer (star connection). If however the main phase 1 touches a local earth such as at your cooker, bang goes the fuse as you try and short out the whole electric grid via the fairly inefficient soil conductor.

As on a generator the incoming is not via live plus distantly earthed neutral, the attachment to a local earth will do nothing to blow fuse, but might mean that you touching live plus any local earth you have, could kill you if any leakage to local neutral.

Which is why railways and many commercial systems use transformer separated earth free systems, often with careful monitoring that there is no earth connection anywhere
 

PaulRainbow

Well-known member
Joined
16 May 2016
Messages
16,883
Location
Suffolk
Visit site
The idea of local earth is to stop mains going back via your body and the ground and killing you if a fault occurs.

However normal mains is relative to earth via the great big 11kv to 450v three phase transformers such that each phase relative to the others is 450 but each phase to an imaginary centre point is 240v. So 240v goes out via one of the phases plus a neutral connected at the transformer (star connection). If however the main phase 1 touches a local earth such as at your cooker, bang goes the fuse as you try and short out the whole electric grid via the fairly inefficient soil conductor.

As on a generator the incoming is not via live plus distantly earthed neutral, the attachment to a local earth will do nothing to blow fuse, but might mean that you touching live plus any local earth you have, could kill you if any leakage to local neutral.

Which is why railways and many commercial systems use transformer separated earth free systems, often with careful monitoring that there is no earth connection anywhere
So what are you saying, no Earth for a generator on a boat ?
 

PaulRainbow

Well-known member
Joined
16 May 2016
Messages
16,883
Location
Suffolk
Visit site
I tried to make sense of someone else's generator/earth thread but it got very angry very quickly, so apologies if this looks like a repeat.

We use a petrol powered genny most of the year as we’re either anchored or on a non electric connected harbour pontoon. The generator has an earth connection which I could easily make with a wire running to the salt water; but the onboard consumer unit doesn’t have a ground to earth connection. Is it possible via a simple skin fitting similar to an anode stud through the hull?

Thank you.
Without knowing the make/model of the generator and how you connect it to the boat, no-0ne can answer your questions. You might think you have the answer, but you probably have not.
 

oldmanofthehills

Well-known member
Joined
13 Aug 2010
Messages
5,061
Location
Bristol / Cornwall
Visit site
So what are you saying, no Earth for a generator on a boat ?
If it is to be earthed it should be to a local earth circuit at the mains sockets such as at the mains sockets as connecting it to the ocean does nothing to provide any fuse blowing capability in an accidental short circuit.

If however the output of the generator is entirely earth free as the 240 has no reference to earth, then connecting the generator chassis or earth to some mains earth circuit in the boat, will do nothing at all

One needs to know what generator manufacturer reccomends
 

PaulRainbow

Well-known member
Joined
16 May 2016
Messages
16,883
Location
Suffolk
Visit site
If it is to be earthed it should be to a local earth circuit at the mains sockets such as at the mains sockets as connecting it to the ocean does nothing to provide any fuse blowing capability in an accidental short circuit.

If however the output of the generator is entirely earth free as the 240 has no reference to earth, then connecting the generator chassis or earth to some mains earth circuit in the boat, will do nothing at all

One needs to know what generator manufacturer reccomends
You do, but equally important is knowing the current standards and regulations for fixed generator installations on boats. The onboard Earth circuit must be connected to the water, as it must for all new boats, whether they have generator or inverter installations or not. Also, generator or inverters must have the neutral and Earth bonded at source. Some come already bonded, some need to be done by the installer. Others cannot be done, therefore they have no place on a boat

This is why the OP needs to say what generator he has and how he connects it to the boat.
 

oldmanofthehills

Well-known member
Joined
13 Aug 2010
Messages
5,061
Location
Bristol / Cornwall
Visit site
Interesting that the current regulations force boat generator to comply with the historic standards used for terrestial house wiring, despite this being theoretically unnecessary. I suppose by forcing earthing of the generator neutral one always gets a known system on board.

I fail to see any virtue in connecting it all to seawater

However as my old research boss kept reminding other engineers at conferences, we dont electrically fully understand lots of stuff, such as what is the reactive, resistive and capacitive model of a long length of steel laid along the ground despite using such for 150 years (ie a railway) so get odd results we cant account for - such as finding 6000A flowing through the ground under london causing extreme decay of the victorian cast iron pillars holding up one station roof.

However the OP is not bound by current boat regulations, so if his generator is guaranteed earth free (ie no connection of neutral to chassis) he could do what he likes.
 

Alex_Blackwood

Well-known member
Joined
19 May 2003
Messages
1,793
Location
Fareham
Visit site
I am not getting involved in this ongoing saga re. generators. Some light reading attached. 😵‍💫 I would also suggest that if you are in anyway unsure of what should be done, you should seek professional advice on site. It all very much depends on how you will be using the generator and your existing system and set up. The articles below are applicable to all installations using portable generators, irrespective of where they are used.
https://dms.niceic.com/0000003348.pdf
MythBusters #6
 

oldmanofthehills

Well-known member
Joined
13 Aug 2010
Messages
5,061
Location
Bristol / Cornwall
Visit site
I am not getting involved in this ongoing saga re. generators. Some light reading attached. 😵‍💫 I would also suggest that if you are in anyway unsure of what should be done, you should seek professional advice on site. It all very much depends on how you will be using the generator and your existing system and set up. The articles below are applicable to all installations using portable generators, irrespective of where they are used.
https://dms.niceic.com/0000003348.pdf
MythBusters #6
Many thanks for that. Sufficiently techy that I can with clear conscience read the stuff on an extended teabreak to complement my IRSE based knowledge so I can push back against bulshit from my E&P colleagues.
 

PaulRainbow

Well-known member
Joined
16 May 2016
Messages
16,883
Location
Suffolk
Visit site
I am not getting involved in this ongoing saga re. generators.
You just have.
Some light reading attached. 😵‍💫 I would also suggest that if you are in anyway unsure of what should be done, you should seek professional advice on site. It all very much depends on how you will be using the generator and your existing system and set up. The articles below are applicable to all installations using portable generators, irrespective of where they are used.
https://dms.niceic.com/0000003348.pdf
MythBusters #6
What does that have to do with fixed installations on a boat ?
 

PaulRainbow

Well-known member
Joined
16 May 2016
Messages
16,883
Location
Suffolk
Visit site
Typical generator/inverter thread, where one or two people know better that the regs, standards and manufacturers and feel qualified to give advice without knowing the equipment that is being installed, how it's being connected and how the existing electrical system if wired. The reason we have standards is so that everyone is playing by the same rules.

I've wasted far too much of my time on generator and inverter threads on this forum, so i'll just say to anyone planning a generator or inverter installation, do you want to install it according to the current standards, regs and manufacturers instructions, or do you want to take the advice of some random bloke on the internet and ignore all of those documents ? Up to you.
 
Last edited:

Tranona

Well-known member
Joined
10 Nov 2007
Messages
42,202
Visit site
This is why the OP needs to say what generator he has and how he connects it to the boat.
Useful to read the OP. He does not have an installed generator, but uses a petrol powered generator, so probably a suitcase one. He also said his 240v system was not earthered. I think I am right in saying those 2 things are not connected other than presumably he has a lead that goes from the generator (sitting in the cockpit?) to the shorepower input.

So really 2 questions. First, does the generator need an earth, second (which I answered) how to earth the 240v system. I don't know the answer to the first.
 

Alex_Blackwood

Well-known member
Joined
19 May 2003
Messages
1,793
Location
Fareham
Visit site
You just have.

What does that have to do with fixed installations on a boat ?
Paul, It doesn't matter if the geny. is in a boat, in a plane or Joe Bloggs garden shed. The proper, safe, installation should be used for what ever system is applicable. Not knocking what you have said but, also, as you have commented, blanket advice without knowing the system and set up, as is this case, is downright dangerous. I think that indeed you have already said that yourself? :unsure:
I fully concur with your #17;)
 

PaulRainbow

Well-known member
Joined
16 May 2016
Messages
16,883
Location
Suffolk
Visit site
Useful to read the OP. He does not have an installed generator, but uses a petrol powered generator, so probably a suitcase one. He also said his 240v system was not earthered. I think I am right in saying those 2 things are not connected other than presumably he has a lead that goes from the generator (sitting in the cockpit?) to the shorepower input.
If that's the case, it's a fixed installation. The fact the generator might be standing on deck or in the cockpit doesn't make the installation portable. If he plugs his kettle into the generator and nothing else, that's portable.
So really 2 questions. First, does the generator need an earth, second (which I answered) how to earth the 240v system. I don't know the answer to the first.
Any generator that is a fixed installation on a boat should have the neutral and Earth bonded and be grounded to the water.

We don't know what the OP has or how it's connected, so cannot provide a definitive solution.

The OP has a history (demonstrated in post #5) of taking an answer that he likes and refusing to give full and proper answers regarding his equipment etc, so it's highly unlikely that we will never know the answers.
 
Top